Systems and methods for focusing charged particle beams

Abstract

A charged particle beam system (300) is disclosed. The charged particle beam system includes a platform (201) configured to hold a sample (203) and capable of moving on at least one of the X-Y-Z axes. The charged particle beam system also includes a positioning sensing system (350, 340) for determining the lateral displacement and vertical displacement of the platform and a beam deflection controller (367), the beam deflection controller (367) being configured to: apply a first signal to deflect a primary charged particle beam (330) incident on the sample to at least partially compensate for the lateral displacement; and apply a second signal to adjust the focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the platform. The first signal and the second signal may include electrical signals having high bandwidths in the range of 10 kHz to 50 kHz and 50 kHz to 200 kHz, respectively. Additionally, a non-transitory computer-readable medium is disclosed, comprising a set of instructions for causing an apparatus (300) to perform a method, the apparatus comprising a charged particle source (310) to generate a primary charged particle beam (314, 330), the method comprising: determining a lateral displacement of a platform (201), wherein the platform is movable in at least one of the X-Y axes; and instructing a controller (367) to apply a first signal to deflect the primary charged particle beam incident on a sample (203) to at least partially compensate for the lateral displacement.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application 62 / 786,131, filed December 28, 2018, and U.S. application 62 / 944,958, filed December 6, 2019, which are incorporated herein by reference in their entireties. Technical Field

[0003] The description herein relates to the field of charged particle beam systems, and more particularly to systems and methods for focusing a charged particle beam and dynamically compensating for vibrations. Background Art

[0004] During the manufacture of integrated circuits (ICs), unfinished or completed circuit assemblies are inspected to ensure that they are manufactured according to design and are free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as scanning electron microscopes (SEMs), may be employed. As the physical size of IC assemblies continues to shrink, the accuracy and yield of defect detection become increasingly important. However, the imaging resolution and throughput of inspection tools struggle to keep pace with the ever-decreasing feature sizes of IC assemblies. The accuracy, resolution, and throughput of such inspection tools may be limited by a lack of precision required for stage motion and control mechanisms.

[0005] Therefore, related art systems face limitations in high-precision stage motion control mechanisms, such as for charged particle beam inspection systems used in semiconductor manufacturing processes. Further improvements in the technology are desired. Summary of the Invention

[0006] Embodiments of the present disclosure provide systems and methods for high-precision three-dimensional platform control for a charged particle beam system. In one aspect of the present disclosure, a charged particle beam system is disclosed. The charged particle beam system includes a platform configured to hold a sample and capable of moving in at least one of an X, Y, and Z axis. The charged particle beam system may also include a positioning sensing system and a controller for determining a lateral displacement and a vertical displacement of the platform, the controller being configured to: apply a first signal to deflect a primary charged particle beam incident on the sample to at least partially compensate for the lateral displacement of the platform; and apply a second signal to adjust the focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the platform. The lateral displacement may correspond to a difference between a target position of the platform on at least one of the X, Y axes and a current position of the platform. The first signal may include an electrical signal that affects how the primary charged particle beam is deflected on at least one of the X, Y axes, and the electrical signal may include a signal having a bandwidth in the range of 10 kHz to 50 kHz.

[0007] In some embodiments, the controller may be further configured to dynamically adjust at least one of the first signal or the second signal during a scan of the primary charged particle beam over the sample. The vertical displacement of the platform may correspond to a difference between a target position of the platform on the Z axis and a current position of the platform, and the vertical displacement may be varied during the scan of the primary charged particle beam over the sample to at least partially compensate for an angular rotation about at least one of the X or Y axes. The second signal may include a voltage signal applied to the platform that affects how the deflected charged particle beam incident on the sample is focused on the Z axis, and the voltage signal may include a signal having a bandwidth in the range of 50 kHz to 200 kHz.

[0008] In some embodiments, the charged particle beam system may include a platform motion controller, wherein the platform motion controller includes a plurality of motors, and these plurality of motors are configured to be independently controlled by the third signal. Each motor in the plurality of motors can be independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the elementary charged particle beam. In some embodiments, the leveling of the adjustment platform can be based on a geometric model of the actuation output of the platform. The third signal may include a plurality of control signals, and each control signal in the plurality of control signals corresponds to at least one motor in the plurality of motors. In some embodiments, a plurality of motors may include at least one of a piezoelectric motor, a piezoelectric actuator, or an ultrasonic piezoelectric motor.

[0009] In some embodiments, the charged particle beam system may further include a first component and a second component, the first component being configured to form an embedded control signal based on a plurality of control signals, and the second component being configured to extract at least one of the plurality of control signals from the embedded control signal. The positioning sensing system of the charged particle beam system may be configured to determine the lateral displacement and the vertical displacement of the platform using a combination of a laser interferometer and a height sensor. In some embodiments, the laser interferometer may be configured to determine the lateral displacement of the platform, and the height sensor may be configured to determine the vertical displacement of the platform.

[0010] In another aspect of the present disclosure, a charged particle beam system is disclosed. The charged particle system may include a platform configured to hold a sample and capable of moving at least in the Z axis. The charged particle beam system may also include a positioning sensing system and a controller, the positioning sensing system being configured to determine the vertical displacement of the platform, and the controller being configured to apply a voltage signal to the platform that affects how the charged particle beam incident on the sample is focused on the Z axis. The vertical displacement of the platform may correspond to the difference between the target positioning of the platform on the Z axis and the current positioning of the platform, and the vertical displacement may vary during a scan of the primary charged particle beam on the sample to at least partially compensate for angular rotation about at least one of the X or Y axes. The controller may also be configured to dynamically adjust the voltage signal during the scan of the primary charged particle beam on the sample.

[0011] In another aspect of the present disclosure, a method for irradiating a sample disposed on a platform in a charged particle beam system is disclosed. The method may include generating a primary charged particle beam from a charged particle source; determining a lateral displacement of a platform, wherein the platform is movable in at least one of an X, Y, and Z axis; and applying a first signal to deflect the primary charged particle beam incident on the sample to at least partially compensate for the lateral displacement of the platform, and applying a second signal to the platform to adjust the focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the platform. The lateral displacement may correspond to a difference between a target position of the platform in at least one of the X, Y axes and a current position of the platform. The vertical displacement of the platform may correspond to a difference between a target position of the platform in the Z axis and a current position of the platform, and the vertical displacement may vary during a scan of the primary charged particle beam over the sample to at least partially compensate for angular rotation about at least one of the X or Y axes. The controller may also be configured to dynamically adjust at least one of the first signal or the second signal during the scan of the primary charged particle beam over the sample. The first signal may include an electrical signal that affects how the primary charged particle beam is deflected in at least one of the XY axes, and the electrical signal may include a signal having a bandwidth in the range of 10 kHz to 50 kHz. The second signal may include a voltage signal applied to the platform that affects how the deflected charged particle beam incident on the sample is focused in the Z axis. The voltage signal may include a signal having a bandwidth in the range of 50 kHz to 200 kHz.

[0012] In some embodiments, a method for irradiating a sample disposed on a platform in a charged particle beam system may further include applying a third signal to a platform motion controller, wherein the platform motion controller includes a plurality of motors configured to be independently controlled by the third signal. The method may further include wherein each of the plurality of motors is independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam. In some embodiments, adjusting the leveling of the platform may be based on a geometric model of an actuation output of the platform. The third signal may include a plurality of control signals, each of the plurality of control signals corresponding to at least one motor of the plurality of motors. In some embodiments, the plurality of motors may include at least one of a piezoelectric motor, a piezoelectric actuator, or an ultrasonic piezoelectric motor.

[0013] In some embodiments, applying the third signal may include embedding a plurality of control signals to form an embedded control signal by a first component of the control module, and extracting at least one of the plurality of control signals from the embedded control signal by a second component of the control module. The position sensing system of the charged particle beam system may be configured to determine the lateral displacement and the vertical displacement of the platform using a combination of a laser interferometer and a height sensor. In some embodiments, the laser interferometer may be configured to determine the lateral displacement of the platform, and the height sensor may be configured to determine the vertical displacement of the platform.

[0014] In another aspect of the present disclosure, a method for irradiating a sample disposed on a platform in a charged particle beam system may include generating a primary charged particle beam from a charged particle source, determining a vertical displacement of the platform, wherein the platform is movable in a Z axis, and applying a voltage signal to the platform to adjust a focus of a deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the platform. The method may also include determining a lateral displacement of the platform, wherein the platform is movable in at least one of an XY axis, and applying a beam deflection signal to deflect the focused charged particle beam incident on the sample to at least partially compensate for the lateral displacement.

[0015] In some embodiments, a method for irradiating a sample disposed on a platform in a charged particle beam system may further include dynamically adjusting at least one of a voltage signal or a beam deflection signal during a scan of the primary charged particle beam over the sample. In some embodiments, the method may further include applying a control signal to a platform motion controller, wherein the platform motion controller includes a plurality of motors, the plurality of motors being configured to be independently controlled by the control signal. Each of the plurality of motors can be independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to an optical axis of the primary charged particle beam.

[0016] In some embodiments, applying the control signal may include embedding the plurality of control signals to form an embedded control signal by a first component of the control module, and extracting at least one of the plurality of control signals from the embedded control signal by a second component of the control module.

[0017] In another aspect of the present disclosure, a non-transitory computer-readable medium includes a set of instructions that can be executed by one or more processors of a charged particle beam device to cause the charged particle beam device to perform the disclosed method. The method can include: determining a lateral displacement of a platform, wherein the platform is movable in at least one of an XY axis; and instructing a controller to apply a first signal to deflect a primary charged particle beam incident on a sample to at least partially compensate for the lateral displacement. The set of instructions that can be executed by one or more processors of the device can cause the device to further execute applying a third signal to a platform motion controller configured to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam.

[0018] In another aspect of the present disclosure, a method for focusing a charged particle beam on a sample is disclosed. The method may include irradiating a sample disposed on a platform of a charged particle beam system with a charged particle beam; adjusting a position of a first focus of the charged particle beam using a first component of the charged particle system and a reference sample; and manipulating an electromagnetic field associated with the sample using a second component to adjust the first focus of the charged particle beam with reference to the sample to form a second focus, wherein the second component is located downstream of a focusing component of an objective lens of the charged particle system. Adjusting the position of the first focus may include adjusting a position of the platform in a Z-axis, and adjusting the position of the platform in the Z-axis may include determining a position of the sample in the Z-axis using a height sensor; and adjusting the position of the platform in the Z-axis based on the determined position of the sample using a platform motion controller. The first component of the charged particle system may be configured to adjust a depth of focus of the charged particle beam with reference to the sample. The first component may be located upstream of a focusing component of the objective lens of the charged particle system. The first component may include a charged particle source, an anode of the charged particle source, or a buncher lens, and the first and second components may be different. Manipulating the electromagnetic field may include adjusting an electrical signal applied to a second component of the charged particle system. The second component of the charged particle system may include one or more of a control electrode of the objective lens, the sample, or a platform. Manipulating the electromagnetic field may include adjusting a first component of the electrical signal applied to the control electrode of the objective lens, or adjusting a second component of the electrical signal applied to the platform. Adjusting the second component of the electrical signal may adjust the landing energy of the charged particle beam on the sample. Adjusting the electrical signal may include adjusting a first component of the electrical signal applied to the control electrode of the objective lens and adjusting a second component of the electrical signal applied to the platform. Adjusting the first component of the electrical signal applied to the control electrode may coarsely adjust a first focal point of the charged particle beam on the surface of the sample, and adjusting the second component of the electrical signal applied to the platform may finely adjust the first focal point of the charged particle beam on the surface of the sample. The first component of the electrical signal may be determined based on an acceleration voltage and landing energy of the charged particle beam. Manipulating the electromagnetic field may include adjusting a magnetic field configured to influence a characteristic of the charged particle beam. The characteristic of the charged particle beam may include at least one of the path, direction, velocity, or acceleration of the charged particle beam.

[0019] In some embodiments, the landing energy of the charged particle beam may be in the range of 500 eV to 3 keV. The first component of the electrical signal may include a voltage signal in the range of 5 kV to 10 kV, and the second component of the electrical signal may include a voltage signal in the range of -150 V to +150 V.

[0020] In another aspect of the present disclosure, a method for focusing a charged particle beam on a sample is disclosed. The method may include: irradiating a sample disposed on a platform with a charged particle beam; adjusting a position of a first focal point of the charged particle beam using a first component of a charged particle system and a reference sample; and manipulating an electromagnetic field associated with the sample by adjusting a first component of an electrical signal applied to a control electrode of an objective lens to form a second focal point by adjusting the first focal point of the charged particle beam on the sample.

[0021] In another aspect of the present disclosure, a charged particle beam system is disclosed. The charged particle beam system may include a platform and a controller configured to hold a sample and movable along at least one of an X, Y, or Z axis, the controller comprising circuitry. The controller may be configured to adjust the position of a first focal point of the charged particle beam using a first component of the charged particle system and a reference sample, and to manipulate an electromagnetic field associated with the sample using a second component to adjust the first focal point of the charged particle beam with reference to the sample to form a second focal point, wherein the second component is located downstream of a focusing assembly of an objective lens of the charged particle system. Adjusting the position of the first focal point may include adjusting the position of the platform in the Z axis. The system may also include a position sensing system configured to determine the position of the sample in the Z axis. The position sensing system may include a height sensor comprising a laser diode sensor assembly. The controller may be configured to adjust the position of the platform in the Z axis based on the position of the sample determined by the position sensing system. The height sensor may be configured to determine the position of the sample in the Z axis, and the controller may be configured to adjust the position of the platform in the Z axis to form the first focal point of the charged particle beam on the sample. The first component can be configured to adjust the depth of focus of the charged particle beam with reference to the sample and can be located upstream of a focusing assembly of an objective lens of the charged particle system. The first component can include a charged particle source, an anode of the charged particle source, or a buncher lens, and the first and second components of the charged particle system can be different. Manipulating the electromagnetic field can include adjusting an electrical signal applied to a second component of the charged particle system. The second component of the charged particle system can include one or more of a control electrode of the objective lens, the sample, or a platform. Adjusting the electrical signal applied to the second component can adjust the landing energy of the charged particle beam on the sample. Adjusting the electrical signal can include adjusting a first component of the electrical signal applied to the control electrode of the objective lens and adjusting a second component of the electrical signal applied to the platform. The controller can also be configured to manipulate the electromagnetic field by adjusting a magnetic field configured to affect a characteristic of the charged particle beam. The characteristic of the charged particle beam can include at least one of the path, direction, velocity, or acceleration of the charged particle beam. Adjusting a first component of the electrical signal applied to the control electrode can coarsely adjust a first focus of the charged particle beam on the sample surface, and adjusting a second component of the electrical signal applied to the platform can finely adjust the first focus of the charged particle beam on the sample surface. The first component of the electrical signal can be determined based on an acceleration voltage and a landing energy of the charged particle beam.

[0022] In some embodiments, the first component of the electrical signal can be determined based on the acceleration voltage and landing energy of the charged particle beam. The first component of the electrical signal can include a voltage signal in the range of 5 kV to 10 kV, and the second component of the electrical signal can include a voltage signal in the range of -150 V to +150 V. The landing energy of the charged particle beam is in the range of 500 eV to 3 keV.

[0023] In another aspect of the present disclosure, a non-transitory computer-readable medium comprising a set of instructions is disclosed, the set of instructions being executable by one or more processors of a device to cause the device to perform a method. The method may include: adjusting a position of a first focus of a charged particle beam using a first component of a charged particle system and a reference sample; and manipulating an electromagnetic field associated with the sample using a second component to form a second focus by adjusting the first focus of the charged particle beam with reference to the sample, wherein the second component is located downstream of a focusing component of an objective lens of the charged particle system. The set of instructions executable by the one or more processors of the device may cause the device to further perform: determining a position of the sample in a Z-axis using a height sensor; and adjusting a position of the stage in a Z-axis based on the determined position of the sample using a stage motion controller to form the first focus of the charged particle beam on the sample. The set of instructions executable by the one or more processors of the device may cause the device to further perform: manipulating the electromagnetic field associated with the sample by adjusting a first component of an electrical signal to coarsely adjust the first focus of the charged particle beam on the sample surface; and adjusting a second component of the electrical signal to the stage to fine-tune the first focus of the charged particle beam on the sample surface.

[0024] In another aspect of the present disclosure, a method for generating a 3D image of a sample in a charged particle beam device is disclosed. The method may include: irradiating a sample disposed on a platform using a charged particle beam; manipulating an electromagnetic field associated with the sample to adjust the focus of the charged particle beam with reference to the sample; forming a plurality of focal planes substantially perpendicular to the main optical axis of the charged particle beam based on the manipulation of the electromagnetic field; generating a plurality of image frames from the plurality of focal planes of the sample, wherein an image frame in the plurality of image frames is associated with a corresponding focal plane in the plurality of focal planes; and generating a 3D image of the sample from the plurality of image frames and the corresponding focal plane information. Manipulating the electromagnetic field may include adjusting a first component of an electrical signal applied to a control electrode of the objective lens or adjusting a second component of an electrical signal applied to the platform.

[0025] In some embodiments, adjusting the second component of the electrical signal can adjust the landing energy of the charged particle beam on the sample. Adjusting the landing energy can include adjusting the first component of the electrical signal to coarsely adjust the first focus of the charged particle beam on the sample surface, and adjusting the second component of the electrical signal to the platform to fine-tune the first focus of the charged particle beam on the sample surface. The first component of the electrical signal can be determined based on the acceleration voltage and landing energy of the charged particle beam. The first component of the electrical signal can include a voltage signal in the range of 5kV to 10kV, and the second component of the electrical signal can include a voltage signal in the range of -150V to +150V. The landing energy of the charged particle beam is in the range of 500eV to 3keV.

[0026] The method may also include forming a first focal plane of the plurality of focal planes that coincides with the top surface of the sample, and a second focal plane of the plurality of focal planes that is a distance below the first focal plane. The distance between the first focal plane and the second focal plane may be dynamically adjusted based on the material of the feature being imaged or the sample. The method may include generating a plurality of image frames at each of the plurality of focal planes of the sample. Generating the 3D image may include reconstructing the plurality of image frames using a reconstruction algorithm.

[0027] In another aspect of the present disclosure, a charged particle beam system is disclosed. The charged particle beam system may include a platform and a controller, the platform being configured to hold a sample and being movable along at least one of an XY axis or a Z axis, the controller having a circuit system. The controller may be configured to: manipulate an electromagnetic field associated with the sample to adjust the focus of the charged particle beam with reference to the sample; form a plurality of focal planes substantially perpendicular to a main optical axis of the charged particle beam based on the manipulation of the electromagnetic field; generate a plurality of image frames from the plurality of focal planes, wherein an image frame in the plurality of image frames is associated with a corresponding focal plane in the plurality of focal planes; and generate a 3D image of the sample from the plurality of image frames and the corresponding focal plane information.

[0028] Manipulation of the electromagnetic field may include adjusting a first component of an electrical signal applied to a control electrode of the objective lens or adjusting a second component of an electrical signal applied to the platform. Adjustment of the second component of the electrical signal may include adjusting the landing energy of the charged particle beam on the sample. Adjustment of the landing energy may include applying the first component of the electrical signal to coarsely adjust a first focus of the charged particle beam on the sample surface; and applying the second component of the electrical signal to the platform to fine-tune the first focus of the charged particle beam on the sample surface. The first component of the voltage signal may be determined based on the acceleration voltage and landing energy of the charged particle beam. The first component of the voltage signal may include a voltage signal in the range of 5 kV to 10 kV, and the second component of the voltage signal may include a voltage signal in the range of -150 V to +150 V. The landing energy of the charged particle beam is in the range of 500 eV to 3 keV.

[0029] In some embodiments, the plurality of focal planes includes a first focal plane and a second focal plane, the first focal plane coinciding with the top surface of the sample, and the second focal plane being formed at a distance below the first focal plane. The distance between the first focal plane and the second focal plane is dynamically adjusted based on the material of the feature or sample being imaged. The controller can be configured to generate a plurality of image frames at each of the plurality of focal planes of the sample, and to generate a 3D image of the sample by reconstructing the plurality of image frames using a reconstruction algorithm.

[0030] In another aspect of the present disclosure, a non-transitory computer-readable medium comprising a set of instructions is disclosed, the set of instructions being executable by one or more processors of a device to cause the device to perform a method. The method may include: irradiating a sample disposed on a platform with a charged particle beam; manipulating an electromagnetic field associated with the sample to adjust the focus of the charged particle beam with reference to the sample; forming a plurality of focal planes substantially perpendicular to a principal optical axis of the charged particle beam based on the manipulation of the electromagnetic field; generating a plurality of image frames from the plurality of focal planes of the sample, wherein an image frame in the plurality of image frames is associated with a corresponding focal plane in the plurality of focal planes; and generating a 3D image of the sample from the plurality of image frames and the corresponding focal plane information.

[0031] In some embodiments, the set of instructions executable by one or more processors of the device may cause the device to further perform: forming a first focal plane among multiple focal planes that coincides with the top surface of the sample; and forming a second focal plane among the multiple focal planes at a predetermined distance below the first focal plane.

[0032] In yet another aspect of the present disclosure, a method for determining vibration of a charged particle beam apparatus is disclosed. The method may include detecting a first vibration of an electro-optical component, the electro-optical component being configured to direct the charged particle beam toward a sample; and detecting a second vibration of an electromechanical component, the electromechanical component being configured to hold the sample, and applying a vibration compensation signal to the electro-optical component to compensate for the first vibration and the second vibration based on the determined vibration of the charged particle beam apparatus. The method may also include adjusting the positioning of the sample with reference to one or more axes, wherein adjusting the positioning of the sample causes vibration of the electro-optical component and the electromechanical component. Detecting the first vibration may include detecting vibration of the electro-optical component about the one or more axes through the use of a first sensor, and wherein the first sensor includes an accelerometer mechanically coupled to the electro-optical component.

[0033] The acceleration sensor may include a piezoelectric sensor, a capacitive accelerometer, a microelectromechanical system (MEMS)-based accelerometer, or a piezoresistive accelerometer, and wherein the first sensor is configured to generate a voltage signal based on the frequency of the detected first vibration. Detecting the second vibration may include detecting vibrations of the electromechanical component on a translational axis and a rotational axis using a second sensor, wherein the second sensor includes a plurality of positioning sensors configured to generate a displacement signal based on the frequency of the detected second vibration. A first positioning sensor of the plurality of positioning sensors may be configured to detect vibrations of the electromechanical component on a translational axis, and wherein a second positioning sensor of the plurality of positioning sensors may be configured to detect vibrations of the electromechanical component on a rotational axis. The method may further include: receiving, by a first controller, a voltage signal and a displacement signal; and determining, using the first controller, a vibration compensation signal based on the received voltage signal and displacement signal. Determining the vibration compensation signal may include: identifying a plurality of vibration patterns based on information associated with the first vibration and the second vibration; estimating vibrations of the electro-optical component and the electromechanical component based on the identified plurality of vibration patterns; determining vibrations along a plurality of axes based on the estimated vibrations of the electro-optical component and the electromechanical component; and determining the vibration compensation signal based on the determined vibrations along the plurality of axes. The vibration compensation signal may be determined to compensate for the vibrations based on an estimate of predicted vibrations for a future time, with reference to the times at which the first vibration and the second vibration were measured.

[0034] Identifying multiple vibration modes may include converting a voltage signal into a corresponding distance signal. Identifying multiple vibration modes may also include decoupling a second vibration of the electromechanical component from a vibration of a housing of the electromechanical component. Estimating the vibration of the electro-optical component and the electromechanical component may include using a simulation model, wherein the simulation model may include a three-dimensional finite element analysis model (3D-FEM), a finite difference analysis model (FDM), or a mathematical analysis model. The method may also include receiving the determined vibration compensation signal via a second controller. The method may also include receiving a beam scanning signal via the second controller; and generating a modified beam scanning signal via the second controller based on the received beam scanning signal and the received vibration compensation signal. The method may also include generating a beam deflection signal via a signal detector based on the modified beam scanning signal, wherein the beam deflection signal is applied to the electro-optical component and used to adjust a characteristic of the charged particle beam incident on the sample. The beam deflection signal may be applied to a beam deflection controller associated with the electro-optical component, wherein the characteristic of the charged particle beam includes a beam scanning speed, a beam scanning frequency, a beam scanning duration, or a beam scanning range. A plurality of positioning sensors may be disposed on a surface of a housing of the electromechanical assembly, and wherein the electro-optical assembly may include a charged particle column, and wherein the electromechanical assembly includes a platform configured to hold a sample and capable of moving in one or more of an X-axis, a Y-axis, or a Z-axis.

[0035] In another aspect of the present disclosure, a charged particle beam system is disclosed. The charged particle beam system may include: a first sensor configured to detect a first vibration of an electro-optical component of the charged particle beam system; a second sensor configured to detect a second vibration of an electromechanical component of the charged particle beam system; and a first controller including a circuit system to generate a vibration compensation signal based on the detected first vibration and second vibration applied to the electro-optical component. The electro-optical component may include a charged particle column and be configured to direct the charged particle beam toward a sample. The electromechanical component may include a platform configured to hold the sample and be movable in one or more of an X-axis, a Y-axis, or a Z-axis. Adjustment of the sample may cause vibrations of the electro-optical component and the electromechanical component.

[0036] The system may further include a housing configured to house an electromechanical assembly of the charged particle beam device. The electromechanical assembly may be mechanically coupled to the housing such that the mobile platform causes vibrations of the housing. The electro-optical assembly may be mechanically coupled to the housing such that vibrations of the housing cause first vibrations of the electro-optical assembly. The first sensor may further be configured to detect first vibrations of the electro-optical assembly about one or more axes. The first sensor may include an acceleration sensor mechanically coupled to the electro-optical assembly. The acceleration sensor may include a piezoelectric sensor, a capacitive accelerometer, a micro-electromechanical system (MEMS)-based accelerometer, or a piezoresistive accelerometer. The first sensor may be configured to generate a voltage signal based on the frequency of the detected first vibration. The second sensor may be configured to detect second vibrations of the electromechanical assembly on a translational axis and a rotational axis. The second sensor may include a plurality of positioning sensors configured to generate a displacement signal based on the frequency of the detected second vibration. A first positioning sensor among the plurality of positioning sensors may be configured to detect vibration of the electromechanical component on a translational axis, and a second positioning sensor among the plurality of positioning sensors may be configured to detect vibration of the electromechanical component on a rotational axis, and the first positioning sensor and the second positioning sensor may be disposed on a surface of a housing of the electromechanical component. The first controller may also be configured to receive a voltage signal and a displacement signal; and determine a vibration compensation signal based on the voltage signal and the displacement signal, and the first controller includes a circuit system to identify a plurality of vibration modes based on information associated with the first vibration and the second vibration; estimate vibrations of the electro-optical component and the electromechanical component based on the identified plurality of vibration modes; determine vibrations on a plurality of axes based on the estimated vibrations of the electro-optical component and the electromechanical component; and determine the vibration compensation signal based on the determined vibrations on the plurality of axes.

[0037] The identification of multiple vibration modes may include converting a voltage signal into a corresponding distance signal. The identification of multiple vibration modes may also include decoupling a second vibration of the electromechanical assembly from a vibration of a housing of the electromechanical assembly. Estimating the vibration of the electro-optical assembly and the electromechanical assembly may include using a simulation model, wherein the simulation model may include a three-dimensional finite element analysis model (3D-FEM), a finite difference analysis model (FDM), or a mathematical analysis model. The system may also include a second controller including circuitry to receive the determined vibration compensation signal. The second controller may include circuitry to receive a beam scanning signal and generate a modified beam scanning signal based on the received beam scanning signal and the vibration compensation signal. The system may also include a signal generator configured to generate a beam deflection signal based on the modified beam scanning signal. The beam deflection signal may be applied to the electro-optical assembly and may be configured to adjust a characteristic of the charged particle beam incident on the sample. The beam deflection signal may be applied to a beam deflection controller associated with the electro-optical assembly. The characteristics of the charged particle beam may include a beam scanning speed, a scanning frequency, a scanning duration, or a beam scanning range. The vibration compensation signal may be determined to compensate for the vibration based on an estimate of the predicted vibration for a future time with reference to the measurement times of the first vibration and the second vibration.

[0038] In another aspect of the present disclosure, a non-transitory computer-readable medium comprising a set of instructions is disclosed, the set of instructions being executable by one or more processors of a device to cause the device to perform a method for determining vibration of a charged particle beam device. The method may include detecting a first vibration of an electro-optical component configured to direct a charged particle beam toward a sample; detecting a second vibration of an electromechanical component configured to hold the sample; and applying a vibration compensation signal to the electro-optical component to compensate for the first vibration and the second vibration based on the determined vibration of the charged particle beam device.

[0039] The set of instructions executable by one or more processors of the device may cause the device to further: adjust the positioning of the sample with respect to one or more axes, wherein adjusting the positioning of the sample causes vibration of the electro-optical component and the electromechanical component. The set of instructions executable by the one or more processors of the device may cause the device to further: determine a vibration compensation signal based on the voltage signal and the displacement signal. Determining the vibration compensation signal may include: identifying a plurality of vibration patterns based on information associated with the first vibration and the second vibration; estimating vibration of the electro-optical component and the electromechanical component based on the identified plurality of vibration patterns; determining vibration along a plurality of axes based on the estimated vibration of the electro-optical component and the electromechanical component; and determining the vibration compensation signal based on the determined vibration along the plurality of axes. The set of instructions executable by one or more processors of the device can cause the device to further perform: receiving a beam scanning signal through a controller; generating a modified beam scanning signal based on the received beam scanning signal and a vibration compensation signal; generating a beam deflection signal through a signal generator based on the modified beam scanning signal, wherein the beam deflection signal is applied to the electro-optical component and is configured to adjust the characteristics of the charged particle beam incident on the sample; and applying the beam deflection signal to a beam deflection controller associated with the electro-optical component. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system consistent with embodiments of the present disclosure.

[0041] Figure 2 is a schematic diagram illustrating an exemplary imaging system consistent with embodiments of the present disclosure.

[0042] Figure 3 is a schematic diagram of an exemplary charged particle beam system consistent with embodiments of the present disclosure.

[0043] Figure 4 is a schematic diagram of an exemplary charged particle beam system consistent with embodiments of the present disclosure.

[0044] Figure 5 is a flow chart illustrating an exemplary method of irradiating a sample consistent with embodiments of the present disclosure.

[0045] Figure 6 is a flow chart illustrating an exemplary method of irradiating a sample consistent with embodiments of the present disclosure.

[0046] Figure 7 is a flow chart illustrating an exemplary method of irradiating a sample consistent with embodiments of the present disclosure.

[0047] Figure 8 is a schematic diagram of an exemplary charged particle beam system consistent with embodiments of the present disclosure.

[0048] Figure 9A is a flow chart illustrating an exemplary method of focusing a charged particle beam on a sample consistent with embodiments of the present disclosure.

[0049] Figure 9B is a flow chart illustrating an exemplary method of focusing a charged particle beam on a sample consistent with embodiments of the present disclosure.

[0050] Figure 10 is a schematic diagram illustrating an exemplary configuration of a charged particle beam system including an electron beam inspection tool consistent with embodiments of the present disclosure.

[0051] Figures 11A to 11F Illustrated are image frames of features on a sample and corresponding focal planes consistent with embodiments of the present disclosure.

[0052] Figure 12 is a schematic diagram of process steps for generating a 3D image reconstructed from image frames captured at multiple focal planes, consistent with embodiments of the present disclosure.

[0053] Figure 13 It shows that the embodiment of the present disclosure is consistent with the Figure 8 Flowchart of an exemplary method for generating a 3D image of a sample in a charged particle beam system.

[0054] Figure 14 is a schematic diagram illustrating the translation axis and the rotation axis of a sample platform in a charged particle beam system consistent with embodiments of the present disclosure.

[0055] Figure 15 is a schematic diagram illustrating an exemplary configuration of a charged particle beam system including an electron beam inspection tool consistent with embodiments of the present disclosure.

[0056] Figure 16 is a schematic diagram illustrating steps of an exemplary algorithm for determining vibration estimate and compensation signals consistent with embodiments of the present disclosure.

[0057] Figure 17 The embodiment consistent with the present disclosure is shown in Figure 15 Flowchart of an exemplary method for focusing a charged particle beam on a sample in a charged particle beam system. DETAILED DESCRIPTION

[0058] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which, unless otherwise indicated, the same reference numerals in different figures represent the same or similar elements. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the present disclosure. Instead, they are merely examples of apparatus and methods consistent with aspects related to the subject matter described in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the present disclosure is not limited thereto. Other types of charged particle beams can be similarly applied. In addition, other imaging systems such as optical imaging, photon detection, X-ray detection, etc. can be used.

[0059] Increasing the computing power of electronic devices while reducing the physical size of the devices can be achieved by significantly increasing the packaging density of circuit components (such as transistors, capacitors, diodes, etc.) on IC chips. For example, in a smartphone, a (thumbnail-sized) IC chip can include over 2 billion transistors, each of which can be less than 1 / 1000 the size of a human hair. Not surprisingly, semiconductor IC manufacturing is a complex process with hundreds of individual steps. Even an error in a single step can significantly affect the functionality of the final product. Even a single "fatal defect" can cause device failure. A goal of the manufacturing process is to increase the overall yield of the process. For example, to achieve a 75% yield for a 50-step process, each individual step must have a yield greater than 99.4%, and if the individual step yield is 95%, the overall process yield drops to 7%.

[0060] As geometries shrink and the IC chip industry migrates to three-dimensional (3D) architectures such as NAND gates, FinFETs, and advanced dynamic random access memory (DRAM), finding defects becomes more challenging and expensive at each lower node. While high process yields are desirable in IC chip manufacturing facilities, it is also important to maintain high wafer throughput, which is defined as the number of wafers processed per hour. High process yields, as well as high wafer throughput, can be impacted by the presence of defects, especially when the defects affect the overall performance of the device and the process yield. Therefore, detecting and identifying micron and nanometer-sized defects while maintaining high throughput is critical to high yield and low cost. In addition to detecting and identifying defects, SEM inspection tools can also be used to identify the source of defects by providing high resolution images combined with elemental analysis of the microstructure on the wafer20.

[0061] Whether or not defects are identified or imaged for routine mid-stage inspection by high-resolution SEM imaging, it will be appreciated that precise stage motion control is critical, particularly where the size of the inspected features or defects is a few tens of nanometers or less. In a high-throughput, high-resolution inspection environment, there may be various factors that can cause measurement errors and can affect the imaging and defect detection capabilities of the inspection tool, such as instrument maintenance, sensor calibration, sample tilt, manufacturing tolerances, processing errors, etc. In practice, the manufacture of very large scale integrated (VLSI) circuits requires precise overlay of each layer within specific tolerance limits, and therefore alignment and precise positioning of the sample stage is very critical. In some cases, the overall overlay tolerance required to produce modern integrated circuits can be less than 40nm. For example, aligning a 200mm wafer to this tolerance can be equivalent to bringing a 50km iceberg to a docking point with an accuracy of 1cm.

[0062] In some cases, the platform can move in six different axes of motion (three translational and three rotational), introducing the possibility of motion errors in each of the six axes. Pitch effects in the X and Y axes caused by the linear movement of the platform can produce Error corresponds to the offset between the plane of the measurement axis and the axis of motion of the stage. Furthermore, existing global and local Z-leveling techniques for the stage may be inadequate or infeasible, in part due to shrinking geometries, but also due to the impact on overall inspection throughput. Some embodiments of the high-precision 3D stage control system proposed in this disclosure can significantly improve stage positioning and motion control accuracy by using high control bandwidth signals and independently controllable piezoelectric actuators for Z-leveling.

[0063] One of several methods for focusing a charged particle beam (e.g., an electron beam) and thereby improving imaging resolution is through the use of optomechanical components, such as adjusting the height of a platform via a piezoelectric transducer. However, the focusing capabilities of optomechanical techniques may not be suitable for some applications in nanofabrication and inspection of devices made therefrom, for example, due to limitations in precise motion control and associated errors, or due to the need to move the platform quickly enough to achieve real-time 3D imaging or achieve target production volumes. Examples of error sources include, but are not limited to, vibrations, temperature gradients, calibration errors, and the like. Therefore, it may be desirable to enhance existing focusing capabilities by enabling the system to further fine-tune the focus of the electron beam while addressing this issue.

[0064] As device density on IC chips increases, device architectures include vertically stacked components and multiple layers for advanced features. Inspection of such devices may require a larger depth of focus so that the top surface, bottom surface, and intermediate layers of the feature can be imaged simultaneously while extracting useful information. For example, measuring the critical dimensions of metal contact holes or detecting buried defective particles can be used to analyze defects, and process conditions can be developed based on information obtained from precise imaging and measurement. Using existing technology to inspect stacked structures such as 3D NAND flash memory devices can provide limited or inaccurate information, both of which may negatively impact the throughput and quality of the devices produced. Therefore, it may be necessary to enable existing inspection tools to have real-time 3D imaging capabilities, such as by adjusting the voltage associated with the platform or lens to cause a change in the electro-magnetic field, which in turn causes a change in the depth of focus of the charged particle beam, thereby increasing the imaging range while maintaining high imaging resolution.

[0065] High-throughput wafer inspection in single-beam and multi-beam inspection systems can be facilitated by the ability to move samples very short distances (e.g., on the order of several nanometers) with high precision and speed. In some applications, vibrations associated with the movement of the stage or SEM column can limit image resolution or inspection throughput, among other things. While existing systems can employ vibration compensation methods to compensate for errors caused by vibration, such compensation methods may be inaccurate due to, for example, insufficient vibration detection, inaccurate compensation, measurement delays, or an inability to accurately correct for vibration in real time.

[0066] In conventional charged particle beam inspection systems, a positioning sensing system is used to determine platform vibration or position a sample along an axis. The positioning sensor is placed on the wall of a chamber that is mechanically coupled to the platform so that platform vibration can be transmitted to the chamber. Although the positioning sensor can accurately determine platform vibration with reference to the chamber, vibration of the chamber, the positioning sensor, or the beam column associated with the chamber may not be detected or may be detected with insufficient accuracy, or the source of the vibration may be indistinguishable. In addition, the positioning sensor used may not detect vibration modes in some translational or rotational axes, resulting in under-compensated or over-compensated vibration compensation signals. Therefore, it is desirable to accurately detect, identify, isolate, and compensate for errors caused by vibration to minimize the loss of imaging resolution. For example, it is desirable to detect vibration and isolate the component of the vibration in the Z dimension. The detected Z vibration component can be analyzed, and the Z vibration at a future time can be predicted relative to the time when the vibration was sensed. Voltages associated with the stage or lens can be adjusted to cause changes in the electromagnetic field, which in turn cause changes in the depth of focus of the charged particle beam to compensate for the predicted vibrations at the times when the vibrations were predicted, resulting in improved accuracy images.

[0067] In one aspect of the present disclosure, a charged particle beam system can be used to observe Figure 2 A wafer (such as a wafer) is provided on a platform 201 Figure 2 Wafer 203). Positioning sensing system (including Figure 3 The height sensor 340 and the laser interferometer 350 can determine the lateral and vertical displacement of the platform. In response to determining the lateral displacement, the beam control module (such as Figure 3 The beam control module 365 of the embodiment of the present invention can apply a first high control bandwidth signal to the beam deflector (such as Figure 3 The charged particle beam system may further include a platform control module (such as a platform control module) to deflect the primary charged particle beam incident on the wafer along a plane substantially perpendicular to the charged particle beam. In response to determining the vertical displacement, the beam control module may apply a second high control bandwidth signal to the platform to adjust the focus of the deflected charged particle beam along a plane substantially parallel to the charged particle beam. Figure 3 Platform control module 362) to apply a third signal to the platform motion controller (including Figure 3 Each of the Z-axis motion controllers 372_1, 372_2, and 372_3 can be independently controlled to adjust the Z-leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam 314.

[0068] In another aspect of the present disclosure, a method for focusing a charged particle beam on a sample is disclosed. The method may include adjusting the position of a first focal point of the charged particle beam with reference to the sample using a first component located upstream of a focusing component of an objective lens of the charged particle system (e.g., an anode of a charged particle source). The position of the first focal point may also be adjusted by adjusting the positioning of a platform on the Z-axis. The method may also include adjusting the first focal point to form a second focal point by adjusting an electromagnetic field of the sample or an electromagnetic field associated with the sample. The electromagnetic field may be adjusted using a second component located downstream of the focusing component of the objective lens of the charged particle system (e.g., a control electrode of the objective lens, platform, or wafer). Adjusting the second component may include applying a first component of an electrical signal to a control electrode of the objective lens to coarsely focus the first focal point, and applying a second component of the electrical signal to the platform to finely focus the first focal point.

[0069] In another aspect of the present disclosure, a method for focusing a charged particle beam on a sample is disclosed. The method includes determining a vibration of a charged particle beam system and applying a vibration compensation signal to a beam column to compensate for the determined vibration of the charged particle beam system. The method may also include detecting vibration of the beam column (electro-optical component) using an acceleration sensor mounted on the beam column, and detecting vibration of a platform (electromechanical component) using a positioning sensor mounted on a housing of the charged particle beam system. The method may also include identifying a vibration mode of the beam column and the platform on each of the translational and rotational axes, estimating the vibration of the beam column based on the identified vibration mode, and predicting the vibration of the beam column and the platform based on the estimated vibration. The method may also include generating a compensated beam scanning signal based on the predicted vibration and the beam scanning signal, and forming a vibration compensation signal to be applied to the beam column of the charged particle system.

[0070] According to an embodiment of the present disclosure, the X, Y and Z axes are Cartesian coordinates. The main optical axis of the charged particle beam device is along the Z axis, and the primary charged particle beam from the charged particle source travels along the Z axis.

[0071] For the sake of clarity, the relative sizes of the components in the drawings may be exaggerated. In the following description of the figures, the same or similar reference numerals refer to the same or similar components or entities, and only the differences with respect to the various embodiments are described.

[0072] As used herein, unless otherwise specifically stated, the term "or" encompasses all possible combinations, except where not feasible. For example, if a database is described as including either A or B, then unless otherwise specified or not feasible, the database may include A, or B, or A and B. As a second example, if a database is described as including A, B, or C, then unless otherwise specified or not feasible, the database may include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C.

[0073] Now refer to Figure 1 , Figure 1 An exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure is illustrated. The EBI system 100 can be used for imaging. Figure 1As shown, the EBI system 100 includes a main chamber 101a, a load / lock chamber 102, an electron beam tool 104, and an equipment front end module (EFEM) 106. The electron beam tool 104 is located within the main chamber 101. The EFEM 106 includes a first load port 106a and a second load port 106b. The EFEM 106 may include (a plurality of) additional load ports. The first load port 106a and the second load port 106b receive front-opening unified pods (FOUPs) containing wafers (e.g., semiconductor wafers or wafers made of (a plurality of) other materials) or samples to be inspected (wafers and samples may be used interchangeably). A batch containing multiple wafers may be loaded for processing as a batch.

[0074] One or more robotic arms (not shown) in the EFEM 106 can transport wafers to the load / lock chamber 102. The load / lock chamber 102 is connected to a load / lock vacuum pump system (not shown), which removes gas molecules from the load / lock chamber 102 to a first pressure below atmospheric pressure. After reaching the first pressure, the one or more robotic arms (not shown) can transport the wafers from the load / lock chamber 102 to the main chamber 101. The main chamber 101 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules from the main chamber 101 to a second pressure below the first pressure. After reaching the second pressure, the wafers are inspected by the electron beam tool 104. The electron beam tool 104 can be a single-beam system or a multi-beam system.

[0075] The controller 109 is electronically connected to the electron beam tool 104. The controller 109 may be a computer configured to perform various controls of the EBI system 100. Figure 1 While shown in FIG. 1 as being external to the structure including the main chamber 101 , the load / lock chamber 102 , and the EFEM 106 , it should be understood that the controller 109 may be part of the structure.

[0076] Figure 2 An exemplary imaging system 200 is illustrated in accordance with an embodiment of the present disclosure. Figure 2 The electron beam tool 104 can be configured for use in the EBI system 100. The electron beam tool 104 can be a single beam device or a multi-beam device. Figure 2As shown, the electron beam tool 104 may include a motorized sample stage 201 and a wafer holder 202 supported by the motorized stage 201 to hold a wafer 203 to be inspected. The electron beam tool 104 also includes an objective lens assembly 204, an electron detector 206 (including electron sensor surfaces 206a and 206b), an objective aperture 208, a buncher lens 210, a beam limiting aperture 212, a gun aperture 214, an anode 216, and a cathode 218. In some embodiments, the objective lens assembly 204 may include a modified swing objective retarding immersion lens (SORIL) including a pole piece 204a, a control electrode 204b, a deflector 204c, and an excitation coil 204d. The electron beam tool 104 may additionally include an energy dispersive X-ray spectrometer (EDS) detector (not shown) to characterize materials on the wafer 203.

[0077] A primary charged particle beam 220 (e.g., an electron beam) can be emitted from the cathode 218 by applying a voltage between the anode 216 and the cathode 218. The primary electron beam 220 passes through the gun aperture 214 and the beam limiting aperture 212, both of which can determine the size of the electron beam entering the buncher lens 210, which resides below the beam limiting aperture 212. The buncher lens 210 focuses the primary charged particle beam 220 before the beam enters the objective aperture 208 to set the size of the primary electron beam before entering the objective assembly 204. The deflector 204c deflects the primary electron beam 220 to facilitate beam scanning on the wafer 203. For example, during a scan, the deflector 204c can be controlled to sequentially deflect the primary electron beam 220 onto different locations on the top surface of the wafer 203 at different points in time to provide data for image reconstruction for different portions of the wafer 203. Furthermore, the deflector 204 c can be controlled to deflect the primary electron beam 220 onto different sides of the wafer 203 at specific locations at different times to provide data for stereoscopic image reconstruction of the wafer structure at that location. Furthermore, in some embodiments, the anode 216 and the cathode 218 can be configured to generate multiple primary electron beams 220, and the electron beam tool 104 can include multiple deflectors 204 c to project the multiple primary electron beams 220 onto different portions / sides of the wafer at the same time to provide data for image reconstruction of different portions of the wafer 203.

[0078] The excitation coil 204d and the pole piece 204a generate a magnetic field that begins at one end of the pole piece 204a and terminates at the other end of the pole piece 204a. The portion of the wafer 203 scanned by the primary electron beam 220 can be immersed in the magnetic field and can become charged, which in turn creates an electric field. The electric field reduces the energy of the primary electron beam 220 striking the wafer 203 near its surface before it strikes the wafer 203. The control electrode 204b, electrically isolated from the pole piece 204a, controls the electric field on the wafer 203 to prevent micro-arching of the wafer 203 and ensure proper beam focusing.

[0079] A secondary electron beam 222 may be emitted from a portion of the wafer 203 upon receiving the primary electron beam 220. The secondary electron beam 222 may form a beam spot on the sensor surfaces 206a and 206b of the electron detector 206. The electron detector 206 may generate a signal (e.g., voltage, current, etc.) representing the intensity of the beam spot and provide the signal to the image processing system 250. The intensity of the secondary electron beam 222 and the resulting beam spot may be varied depending on the external or internal structure of the wafer 203. Furthermore, as described above, the primary electron beam 220 may be projected onto different locations on the top surface of the wafer or different sides of the wafer at specific locations to generate secondary electron beams 222 (and the resulting beam spots) of different intensities. Thus, by mapping the intensity of the beam spot using the position of the wafer 203, the processing system may reconstruct an image reflecting the internal or external structure of the wafer 203.

[0080] The imaging system 200 can be used to inspect a wafer 203 on a platform 201 and includes the electron beam tool 104 described above. The imaging system 200 can also include an image processing system 250, which includes an image acquisition device 260, a storage device 270, and a controller 109. The image acquisition device 260 can include one or more processors. For example, the image acquisition device 260 can include a computer, a server, a mainframe, a terminal, a personal computer, any type of mobile computing device, or the like, or a combination thereof. The image acquisition device 260 can be connected to the detector 206 of the electron beam tool 104 via a medium such as an electrical conductor, a fiber optic cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, a wireless radio, or a combination thereof. The image acquisition device 260 can receive signals from the detector 206 and can construct an image. The image acquisition device 260 can thus acquire an image of the wafer 203. The image acquisition device 260 can also perform various post-processing functions, such as generating a profile, overlaying indicators on the acquired image, and the like. The image acquirer 260 may be configured to adjust the brightness and contrast of the acquired image. The storage 270 may be a storage medium such as a hard disk, a random access memory (RAM), or other types of computer-readable memory. The storage 270 may be coupled to the image acquirer 260 and may be used to save the scanned raw image data as original images and save post-processed images. The image acquirer 260 and the storage 270 may be connected to the controller 109. In some embodiments, the image acquirer 260, the storage 270, and the controller 109 may be integrated as a control unit.

[0081] In some embodiments, image acquirer 260 may acquire one or more images of the sample based on the imaging signal received from detector 206. The imaging signal may correspond to a scanning operation for conducting charged particle imaging. The acquired image may be a single image including multiple imaging regions. The single image may be stored in storage 270. The single image may be an original image that may be divided into multiple regions. Each of the regions may include an imaging region containing a feature of wafer 203.

[0082] Now refer to Figure 3 , Figure 3 is an exemplary charged particle beam system consistent with embodiments of the present disclosure. In some embodiments, the charged particle beam system 300 includes a charged particle beam column 310, a primary charged particle beam 314 having an optical axis 312, a buncher lens 315 (similar to Figure 2The charged particle beam system 300 may be a beam condenser lens 210, a deflector array 320 (which deflects the primary charged particle beam 314 and forms a deflected charged particle beam 330 irradiated on the wafer 203 (which is provided on the platform 201), a height sensor 340, a laser interferometer 350, a system control module 360 ​​including a platform control module 362 and a beam control module 365, a beam deflection controller 367, a platform motion controller 370 including a Z-axis motion controller 372, and an XY-axis motion controller 374. Alternatively, the charged particle beam system 300 may be Figure 1 EBI system 100 or Figure 2 It should be understood that in the context of the present disclosure, charged particles and electrons can be used interchangeably. Similarly, elements of the claimed apparatus or method describing (multiple) charged particle beams can be used interchangeably with (multiple) electron beams, as appropriate.

[0083] In some embodiments, the charged particle beam system 300 may include an electron beam system or an electron beam inspection system. The charged particle beam system 300 may include a charged particle beam column 310 that may house a plurality of particles such as Figure 2 The cathode 218, anode 216, gun aperture 214, and beam limiting aperture 212 are shown. A primary charged particle beam 314 can be emitted from the cathode 218 by applying a voltage between the anode 216 and the cathode 218. In some embodiments, the primary charged particle beam 314 can be an electron beam that passes through the gun aperture 214 and the beam limiting aperture 212, both of which can determine the electron beam entering the buncher lens 210 (similar to Figure 3 The deflector array 320 can deflect the primary charged particle beam 314 to facilitate beam scanning on the wafer 203.

[0084] The deflector array 320 can include a single deflector, a plurality of deflectors, or an array of deflectors to deflect the primary charged particle beam 314 away from the optical axis 312. The beam deflection can be configured to scan the primary charged particle beam 314 across the wafer 203 during irradiation or inspection. Because the primary charged particle beam 314 is deflected away from the optical axis 312, additional aberrations may be introduced, resulting in pattern distortion. Deflecting the primary charged particle beam 314 can be accomplished electrostatically or magnetically. Magnetic deflectors allow for a longer deflection range than electrostatic deflectors, but their frequency response may be limited by the inductance of the magnetic coils and eddy currents introduced by the magnetic field.

[0085] In some embodiments, the charged particle beam system 300 may include a source conversion unit ( Figure 3 The source conversion unit may include an image forming element array ( Figure 3not shown), an aberration compensator array and a beam limiting aperture array (such as comprising Figure 2 The image forming element array may include a plurality of microdeflectors or microlenses to form a plurality of parallel images (virtual or real) of the plurality of beam waves of the primary electron beam 314. The beam limiting aperture array may limit the plurality of beam waves. It should be understood that the source conversion unit 120 may be configured to process any number of beam waves.

[0086] The buncher lens 315 can be configured to focus the primary charged particle beam 314. In some embodiments, the buncher lens 315 can also be configured to adjust the current of the primary beam waves of the primary charged particle beam 314 downstream of the source conversion unit by changing the focusing power of the buncher lens 315. Alternatively, the current can be changed by changing the radial size of the beam-limiting apertures 212 corresponding to the respective primary beam waves within the beam-limiting aperture array.

[0087] In some embodiments, the charged particle beam system 300 may include a primary projection optical system ( Figure 3 The primary projection optical system may include an objective lens assembly 204, a beam splitter and a deflection scanning unit (such as, Figure 3 The beam splitter may be, for example, a device that generates an electrostatic dipole field E1 and a magnetic dipole field B1 (both at Figure 3 In some embodiments, the beam splitter 314 may be configured to apply an electrostatic force to each charged particle of the primary charged particle beam 314 via an electrostatic dipole field E1. The electrostatic force is equal in magnitude to, but opposite in direction to, the magnetic force applied to each electron by the magnetic dipole field B1 of the beam splitter. The primary charged particle beam 314 may thus pass through the beam splitter at least substantially straight with a deflection angle that is at least substantially zero. In some embodiments, the deflection scanning unit 330 may be configured to deflect the primary charged particle beam 314 so that the deflected charged particle beam 330 scans a probe spot across each scanning area on the wafer 203.

[0088] In practice, wafer 203 can be observed with high magnification in charged particle beam system 300 or EBI system 100, and platform 201 can stably support wafer 203 and move steadily along horizontal XY axis, vertical Z axis, platform tilt or platform rotation. When the movement on X and Y axis can be used for the selection of field of view (FOV), the movement on Z axis can be required to be used for the change of image resolution, depth of focus etc. Platform 201 can be, for example, a fully centered platform. In the fully centered platform, the observation area and the focusing on the wafer surface are not shifted when tilting wafer 203.

[0089] In some embodiments, the positioning sensing system ( Figure 3340 and a laser interferometer 350. It should be understood that the positioning sensing system may include more than one height sensor 340 and more than one laser interferometer 350 and other suitable components, as well as signal amplifiers, bandpass filters, data storage units, data processing units, etc.

[0090] In some embodiments, the height sensor 340 can be used to determine the longitudinal displacement of the platform 201. As referred to herein, the vertical displacement of the platform 201 can correspond to the difference between the actual position of the platform 201 on the Z axis and the target position. An optical height sensor (such as Figure 3 The height sensor 340 shown in FIG3 may comprise a laser diode sensor assembly comprising a one-dimensional position sensitive detector (1-D PSD) or a linear array of photodiodes, etc. The height sensor 340 may communicate with a system control module 360 ​​(described in detail later) so that the output of the height sensor 340 is analyzed and used to further adjust the platform positioning. In some embodiments, the output data from the height sensor 340 may be used to create a tunable electric field on the surface of the sample by applying a voltage to the platform, or to modify the beam focusing by adjusting the current applied to the objective lens assembly 204 or by applying a voltage to the platform and objective lens assembly 204. It should be understood that other suitable components for focusing the incident beam may be employed. One or more optical height sensors, such as the height sensor 340, may be employed based on the complexity and accuracy of the height sensing required. Other height sensing technologies may be appropriately used.

[0091] In some embodiments, the vertical displacement of the platform 201 can be routinely determined based on height measurement or height sensing of a standard sample for device calibration. For example, a wafer 203 including standard patterned features (such as metal lines, photoresist layers, reflective films deposited on the wafer 203, etc.) can be used to calibrate a device, sensor, motor, or platform.

[0092] The high throughput inspection in the wafer in production facilities (such as wafer factories) may require platform 201 to move quickly and accurately in the repetitive pattern of start-stop motion. The start-stop motion can include multiple high accelerations, decelerations and stable cycles of platform 201, with the order of magnitude travel distance of several microns or nanometers. With high speed and high acceleration mobile platform 201 can generate the vibration caused by system dynamics, this vibration can in turn cause dynamic resonance in the system, for example, the vibration wave constructively interferes to cause the higher amplitude vibration of whole charged particle beam system 300. The vibration caused by mobile platform 201 may cause translation error or displacement error on more than one axis. For example, when checking the die on wafer 203, the platform 201 moving on the XY axis can cause dynamic resonance with other mobile or non-mobile components to cause the platform vibration on the Z axis. The accurate positioning of platform 201 may require accurate positioning measurement technology, such as, for example, the optical height sensor using a laser.

[0093] In some embodiments, the laser interferometer 350 can be used to measure translational displacement in the XY axis and to precisely position the stage 201 in the XY axis. Laser interferometer displacement measurement technology is commonly used as a high-accuracy displacement measurement method to control the movement of equipment (e.g., steppers) used in photolithography processes for manufacturing semiconductor devices and for controlling XY stages.

[0094] In some embodiments, the laser interferometer 350 can be, for example, a homodyne laser interferometer or a heterodyne laser interferometer. A homodyne laser interferometer uses a single-frequency laser source, while a heterodyne laser interferometer uses a laser source with two close frequencies. The laser source can include a He-Ne gas laser that emits laser light at a wavelength of 633 nm. Other laser sources emitting at single or multiple wavelengths or frequencies can also be used. In some embodiments, more than one laser interferometer can be used. A combination of homodyne and heterodyne laser interferometers can be used within the system.

[0095] In some embodiments, laser interferometer 350 may be used to determine the lateral displacement of platform 201. As referred to herein, lateral displacement may correspond to the difference between the actual position of platform 201 and the target position in at least one of the X and Y axes. In practice, more than one laser interferometer (such as Figure 3In one embodiment, the laser interferometer 350 shown in FIG2 is used to determine the lateral displacement. Since the deflection of the primary charged particle beam 314 is limited in the cell, accurate mechanical platform positioning may need to be combined with beam deflection by exposing multiple deflection fields and splicing them together to pattern large features. This can be achieved by using two laser interferometers (such as laser interferometer 350) to measure the platform positioning on the X and Y axes. In some embodiments, the two split laser beams can be directed to a reference mirror and a mirror attached to the platform in each direction, and then the interferometer can compare the positioning of the platform mirror with the positioning of the reference mirror to detect and correct any platform positioning error. For example, one laser interferometer is used for the X axis, and a second laser interferometer is used for the Y axis. In some embodiments, more than one laser interferometer can be used for a single axis, such as the X or Y axis. Other suitable technologies can also be used.

[0096] refer to Figure 3 , the charged particle beam system 300 may include a system control module 360. The system control module 360 ​​may include a platform control module 362 and a beam control module 365. The system control module 360 ​​may be configured to communicate with the height sensor 340, the laser interferometer 350, and the platform motion controller 370. The system control module 360 ​​may be configured to receive a signal from the height sensor 340 and process the received signal based on the determined vertical displacement of the platform 201. The system control module 360 ​​may also be configured to receive a signal from the laser interferometer 350 and process the received signal based on the determined lateral displacement of the platform 201. In some embodiments, the system control module 360 ​​may include a user interface (not shown) to receive user input based on the determined lateral and vertical displacements of the platform 201. The user interface may be, for example, a visual touch screen, a screen with user controls, an audio-visual interface, or the like.

[0097] In some embodiments, the system control module 360 ​​may include a platform control module 362 and a beam control module 365. The platform control module 362 may be, for example, a circuit board including various circuits for platform positioning and motion control. Other components may also be mounted on the circuit board, including sequencer circuits, timer circuits, signal processing circuits, etc.

[0098] In some embodiments, the platform control module 362 of the system control module 360 ​​may include a signal processing circuit. The signal processing circuit of the platform control module 362 may be configured to receive a signal from the height sensor 340 or the laser interferometer 350. In some embodiments, the platform control module 362 may be configured to receive a signal from the laser interferometer 350. The signal processing circuit may determine the vertical displacement degree of the platform 201 or the lateral displacement degree of the platform 201 based on the received signal. The received signal may be, for example, an optical signal, an electrical signal, or a combination thereof.

[0099] In some embodiments, the system control module 360 ​​may include a beam control module 365 having a beam deflection controller 367, also referred to herein as a controller. In some embodiments, the beam deflection controller 367 may be configured to apply a first signal to deflect the primary charged particle beam 314 incident on the sample (e.g., wafer 203) to at least partially compensate for lateral displacement of the stage 201. The beam deflection controller 367 may be configured to apply a second signal to adjust the focus of the deflected charged particle beam 330 incident on the wafer 203 to at least partially compensate for vertical displacement of the stage.

[0100] In some embodiments, the beam deflection controller 367 can be configured to dynamically adjust at least one of the first signal and / or the second signal during scanning of the primary charged particle beam 314 over the wafer 203. As used herein, dynamically adjusting a signal can refer to continuously and iteratively adjusting a signal as a sample is scanned or inspected. For example, the positioning of the platform 201 can be continuously monitored, measured, recorded, and communicated to a controller such as the beam deflection controller 367. Upon receiving updated positioning information including lateral displacement, vertical displacement, and / or pitch and roll error information, the beam deflection controller 367 can adjust the signal to at least partially compensate for the displacement based on the received information. As wafer scanning continues, the platform positioning and displacement information can be continuously collected, exchanged, and used by the beam deflection controller to adjust the signal.

[0101] The beam deflection controller 367 may be, for example, a control loop feedback mechanism including a proportional-integral-derivative (PID) controller, a proportional-integral (PI) controller, a proportional controller (P), etc. In some embodiments, the laser interferometer 350 may communicate directly with the beam control module 365 or the beam deflection controller 367 configured to deflect the primary charged particle beam 314 incident on the wafer 203.

[0102] In some embodiments, the laser interferometer 350 can be connected to the platform control module 362 or the beam control module 365 ( Figure 3In some embodiments, the laser interferometer 350 can communicate with the beam control module 365 via the platform control module 362. For example, the laser interferometer 350 can communicate with the signal processing circuitry (not shown) of the platform control module 362 and generate a signal for the beam control module 365 to deflect the incident beam corresponding to the determined lateral displacement or position of the platform 201. At least partially compensating for the lateral displacement of the platform in the XY axis may also be referred to herein as XY dynamic compensation. Figure 3 One laser interferometer 350 is shown configured to determine the position or lateral displacement of the platform 201 , however, more than one interferometer may be used as appropriate.

[0103] In some embodiments, the electrical signal applied to the deflector array 320 by the beam control module 365 may include a signal having a control bandwidth in the range of 10 kHz to 50 kHz. As used herein, the bandwidth ωB of the control system may be defined as the frequency range in which the magnitude of the closed-loop frequency response is greater than -3 dB in the frequency domain.

[0104] Image resolution is directly dependent on the positioning of the sample or wafer 203. In addition to resolution, the repeatability and stability of the platform positioning can be critical to the quality of the image. Movement or small-scale vibrations of the platform 201 or wafer 203 during scanning can significantly affect image quality and adversely affect the defect detection capabilities of the inspection tool. If sample drift does not occur once the target positioning is achieved, image distortion can be avoided. The positioning platform (e.g., platform 201) can be required to move smoothly at speeds of several nanometers per second (nm / s).

[0105] In some embodiments, the platform motion controller 370 can control the movement of the platform 201 in the X, Y, or Z axis. The platform motion controller 370 may include a Z-axis motion controller 372 for moving the platform 201 in the Z axis and an XY-axis motion controller 374 for moving the platform 201 in at least one of the X and Y axes. The platform motion controller 370 may include, for example, a piezoelectric stepper driver and actuator, an ultrasonic piezoelectric motor, a piezoelectric motor, a piezoelectric actuator, etc. In some embodiments, the platform motion controller 370 may communicate with and receive signals from the platform control module 362 based on the determined vertical or lateral displacement of the platform 201. Figure 3 As shown, the Z-axis motion controller 372 may also include more than one piezoelectric driver or piezoelectric actuator. The XY-axis motion controller 374 may also include more than one piezoelectric driver or piezoelectric actuator.

[0106] To improve image resolution and contrast, the user can apply a beam modification voltage to reduce or increase the beam energy of the incident beam on the wafer 203. In some embodiments, the platform 201 can be maintained at a high bias voltage so that the charged particles leaving the charged particle beam column 310 are decelerated before the charged particle beam reaches the wafer 203 or the platform 201. For example, in a secondary electron microscope, if the high voltage (the accelerating voltage applied in the column) is -5 kV and the platform bias is -4 kV, the electrons are first accelerated to an energy of 5 keV in the column and then decelerated by 4 keV after leaving the column, so that without beam deceleration, the effective high voltage is -1 kV. In some embodiments, the platform 201 can be maintained at a high bias voltage so that the charged particles leaving the charged particle beam column 310 are accelerated before they reach the wafer 203 or the platform 201. Applying a platform bias can be used to modify the beam energy and focus of the charged particle beam in the Z axis. The incident beam charged particle beam may include the primary charged particle beam 314 or the deflected charged particle beam 330 .

[0107] In some embodiments, as Figure 3 As shown, the voltage signal applied to the platform 201 via the platform motion controller 370 can be, for example, an alternating current (AC) voltage signal. The applied voltage signal can be based on the determined vertical displacement of the platform 201 to at least partially compensate for the vertical displacement. At least partially compensating for the vertical displacement of the platform in the Z axis may also be referred to herein as Z dynamic compensation.

[0108] In some embodiments, the voltage signal may include a signal having a control bandwidth in the range of 50kHz to 200kHz, 60kHz to 180kHz, 70kHz to 160kHz, 80kHz to 140kHz, 90kHz to 120kHz, 100kHz to 110kHz, or any suitable range. In some embodiments, a preferred control bandwidth of the voltage signal applied to platform 201 may be 100kHz.

[0109] In practice, moving the platform 201 along any of the X, Y, and Z axes may introduce a pitch effect. Specifically, pitch effects along the X and Y axes may generate Abbé errors, which, if not accounted for, may lead to inaccurate platform positioning. As mentioned herein, the pitch effect of the platform 201 along the X axis may be defined as the angular rotation or tilt of the platform 201 about the Y axis, and the pitch effect of the platform 201 along the Y axis may be defined as the angular rotation or tilt of the platform 201 about the X axis. It should be understood that angular rotation about the X axis is referred to as roll. During scanning of the wafer 203 (disposed on the platform 201), compensation for pitch effects along the X and Y axes may require simultaneous and continuous compensation for lateral displacement (X and Y axes) and vertical displacement (Z axis). Vertical displacement can be compensated for by adjusting the focus of the incident beam on the wafer 203 or by adjusting the positioning of the platform 201 along the Z axis. In some embodiments, the measured xy coordinates may be corrected based on the determined Abbé errors from the pitch effects along the X and Y axes. The corrected xy coordinates of the platform 201 may include displacements due to pitch effects.The beam deflection controller 367, beam control module 365, and platform control module 362 may communicate with one or more laser interferometers to receive updated platform positioning information.

[0110] In some embodiments, a laser interferometer (such as Figure 3 The laser interferometer 350 can be configured to measure compensation that is required to account for the pitch effect on the XY axis. For example, the charged particle beam system 300 can include three laser interferometers, each of which is used for a predefined function. The first laser interferometer can be used to determine the lateral displacement on the X axis, the second laser interferometer can be used to determine the lateral displacement on the Y axis, and the third laser interferometer can be used to determine the pitch effect on the XY axis. It should be understood that more than three laser interferometers can be used as needed.

[0111] like Figure 4 As shown, the Z-axis motion controller 372 can include three Z-axis motion controllers, such as, for example, actuators 372_1, 372_2, and 372_3, each of which is configured to communicate independently with the platform control module 362. It should be understood that more Z-motion controllers can be used as needed. For example, a platform 201 holding 300mm wafers can utilize more Z-motion controllers than a platform holding 200mm wafers, or a platform 201 of an online charged particle beam inspection tool can utilize more Z-motion controllers than an offline tool. Independent control of each Z-motion controller in the Z-motion controllers (such as, actuators 372_1, 372_2, and 372_3) can assist in Z leveling of the platform 201.

[0112] In certain embodiments, the accurate positioning of platform 201 can comprise the accurate leveling of platform, makes platform 201 and therefore the wafer 203 that is arranged on platform 201 perpendicular to the optical axis 312 of charged particle beam system 300.The leveling of platform 201 can be constantly monitored by height sensor 340.When determining that platform 201 is non-planar based on the signal received from height sensor 340, platform control module can generate and be configured to move one or more Z motion controllers (such as actuator 372_1) to modify the signal of platform leveling.A plurality of height sensors can be used to monitor level, vertical displacement and platform positioning on the Z axis.Platform control module 362 can be configured to receive signal from each height sensor in a plurality of height sensors.

[0113] In some embodiments, the platform control module 362 further includes a signal processing circuit 410, which includes one or more components (such as, for example, a signal converter 415) configured to convert an optical signal into an electrical signal before processing the signal and generating an output signal. The signal processing circuit 410 can be, for example, a processor, a microprocessor, a control circuit, an application specific integrated circuit (ASIC), an integrated circuit, a computing device, a computer, a controller, etc. Other suitable devices and modules may also be used.

[0114] In some embodiments, the signal processing circuit 410 may include a signal aggregation circuit 412 configured to embed multiple signals from the height sensor 340 into a single signal. In some embodiments, the signal aggregation circuit 412 may be configured to receive one or more signals from the signal converter 415. In some embodiments, the signal aggregation circuit 412 may include a multiplexer circuit configured as a multiple-input, single-output switch. For example, the signal aggregation circuit 412 may receive multiple input signals from the height sensor 340 indicating the platform height across a particular spot on the wafer 203. In some embodiments, the signal aggregation circuit 412 may receive multiple signals from each of the multiple height sensors and process the received signals to determine whether the platform 201 is leveled. In some embodiments, the multiple signals from the height sensor 340 may be used to determine the vertical displacement of the platform 201 or the positioning of the platform 201.

[0115] In some embodiments, the signal aggregation circuit 412 may include a code division multiplexer, a frequency division multiplexer, a time division multiplexer, a wavelength division multiplexer, or a statistical multiplexer. In some embodiments, the multiplexer circuit may include, for example, a 2-input 1-input multiplexer, a 4-input 1-input multiplexer, an 8-input 1-input multiplexer, or a 16-input 1-input multiplexer. Other signal processing circuit types and configurations may also be used.

[0116] In some embodiments, the platform motion controller 370 may include a signal separation circuit 414. The signal separation circuit may be, for example, a demultiplexer circuit configured as a single-input, multiple-output switch. The signal separation circuit 414 may be configured to receive a single output signal from the signal aggregation circuit 412 and generate multiple output signals to actuate one or more Z-axis motion controllers 372 or XY-axis motion controllers 374. For example, when the control bandwidth of the voltage signal applied to the platform 201 is 100 kHz, the voltage signal may include three separate signals embedded in the Z-axis motion controller, one signal for each of the three Z-axis motion controllers.

[0117] In some embodiments, platform motion controller 370 may be configured to receive signals from signal aggregation circuit 412. Platform motion controller 370 may process the received signals based on the determined lateral or vertical displacement and the required compensation.

[0118] In some embodiments, each of the plurality of output signals of the signal decoupling circuit 414 can control a Z-axis motion controller. Figure 4 As shown, each output signal is associated with each of the Z-axis motion controllers. In some embodiments, two output signals can be combined to control one Z-axis motion controller. Alternatively, one output signal from the signal segregation circuit 414 can control both Z-axis motion controllers. It should be understood that numerous combinations of output signals associated with the Z-axis motion controllers may be possible.

[0119] In some embodiments, the output signal from the signal decomposition circuit 414 can control the XY axis motion controller 374 based on the lateral displacement of the platform 201 determined by the laser interferometer 350. The platform motion controller 370 can include other circuits and components for routing signals, timing signals, filtering signals, etc.

[0120] In some embodiments, the signal aggregation circuit 412 and the signal segregation circuit 414 may include functional logic gates such as AND, OR, NAND, NOR, or combinations thereof. The combinational logic gates may interface with one or more of the system control module 360 ​​or the platform motion controller 370 .

[0121] In some embodiments, Z-axis leveling of the platform 201 can be achieved by controlling the height of a vertical actuator (e.g., a piezoelectric motor) using geometric model information calculated from the actuation output. The geometric model can include a mechanical model of the platform, a computer-aided drawing (CAD) of the platform, simulation of the platform's dimensions, and actuation of the platform's movement.

[0122] Figure 5 is a flow chart illustrating an exemplary method of irradiating a sample with a charged particle beam using a charged particle beam system consistent with an embodiment of the present disclosure. The method of observing the sample may be performed by Figure 3 Charged particle beam system 300, Figure 8 Charged particle beam system 800 (discussed later) or Figure 1 It will be appreciated that the charged particle beam system can be controlled to observe, image, and inspect wafers (e.g., Figures 2 to 3 The imaging process may include scanning the wafer to image at least a portion of the wafer, a pattern on the wafer, or the wafer itself. The inspection process may include scanning the wafer to inspect at least a portion of the wafer, a pattern on the wafer, or the wafer itself.

[0123] In step 510, a primary charged particle beam (e.g., Figure 2 A primary charged particle beam 220) is generated from a charged particle source. In some embodiments, a charged particle beam may refer to a spatially positioned group of charged particles having approximately the same kinetic energy and direction. The charged particles may include electrons, protons, or ions. The charged particle source may be, for example, thermionic emission of electrons from a tungsten hexaboride or lanthanum hexaboride (Lab6) cathode, or electric field induced electron emission of electrons from tungsten oxide / zirconium (ZrO2), etc. The charged particle beam may include charged particles with high kinetic energy due to a high accelerating electric field, so that the charged particles are driven toward the sample. The kinetic energy of the charged particles may be in the range of 0.2-40 keV or higher. In some embodiments, the primary charged particle beam may have an optical axis (e.g., optical axis 312) along which the beam is directed toward a wafer or platform (e.g., Figure 2-Figure 3 Platform 201) moves forward.

[0124] In step 520, the lateral displacement of the platform can be determined. As used herein, lateral displacement can refer to the difference between the target location and the current location of the platform on the XY axis. In a charged particle beam system, there may be multiple factors that cause the lateral displacement of the platform. For example, mechanical vibration, electromagnetic interference from stray fields, temperature changes due to lens heating, errors due to platform tilt, etc.

[0125] In some embodiments, the lateral displacement of the platform can be determined using precise optical position sensing techniques. Laser interferometers (e.g., Figure 3 The laser interferometer 350 can be used to determine the lateral displacement of the platform in the XY axis. One or more laser interferometers can be used in conjunction with a beam control module (e.g., Figure 3 The beam control module 365 of the embodiment of the present invention communicates directly with the beam control module (e.g., Figure 3The beam control module 362 communicates indirectly with the platform control module 362. One or more laser interferometers can be configured to determine the lateral displacement of the platform based on signals detected by photodetectors of the laser interferometers. In some embodiments, the beam control module, the platform, and the laser interferometers can form a closed feedback control loop.

[0126] In step 530, upon determining the lateral displacement of the stage, the beam deflection controller of the beam control module may apply a signal to the primary beam deflector (e.g., Figure 3 The applied signal can deflect the primary charged particle beam in the X or Y axis or both axes to at least partially compensate for the lateral displacement of the platform. The applied signal can include an electrical signal with a bandwidth in the range of 10kHz to 50kHz. In a preferred embodiment, the bandwidth of the applied signal can be 30kHz.

[0127] Figure 6 is a flow chart illustrating an exemplary method of irradiating a sample with a charged particle beam using a charged particle beam system consistent with embodiments of the present disclosure. The method of observing the sample may be performed by Figure 3 Charged particle beam system 300 or Figure 1 The EBI system 100 is used to perform.

[0128] In step 610, similar to step 510, a primary charged particle beam (e.g., Figure 2 The primary charged particle beam 220 is generated from a charged particle source. The primary charged particle beam can be, for example, an electron beam generated from an electron source. The electron source can include, but is not limited to, thermionic emission of electrons from a tungsten filament or a Lab6 cathode, or field emission of electrons from a tungsten / ZrO2 cold cathode.

[0129] In step 620, the platform (e.g., Figure 2-Figure 3 In another embodiment, the vertical displacement of the platform 201 can be determined. As used herein, vertical displacement can refer to the difference between the target positioning of the platform on the Z axis and the current positioning. In charged particle beam systems, there may be a plurality of factors causing the vertical displacement of the platform. For example, mechanical vibration, electromagnetic interference from stray fields, platform movement calibration error, piezoelectric motor calibration error etc.

[0130] In some embodiments, the vertical displacement of the platform can be measured using an optical height sensor (e.g., Figure 3 The height sensor 340 is determined using precise optical positioning sensing technology. The height sensor may include a laser diode assembly including a radiation platform or a wafer disposed on the platform (e.g., Figure 2-Figure 3The height sensor can be connected to a platform control module (e.g., Figure 3 Platform control module 362), beam control module ( Figure 3 beam control module 365) or both.

[0131] In step 630, upon determining the vertical displacement of the platform, the beam deflection controller (e.g., Figure 3 The beam deflection controller 367) can apply a signal to the platform to adjust the positioning of the focal plane of the primary charged particle beam on the Z axis by moving the platform along the Z axis. In certain embodiments, the vertical movement of the platform can be performed at least in part using an actuator such as, for example, a piezoelectric motor, a piezoelectric actuator, or an ultrasonic piezoelectric motor or a combination thereof. The signal applied can comprise a voltage signal with a bandwidth in the scope of 50kHz to 200kHz. In a preferred embodiment, the bandwidth of the signal applied can be 100kHz.

[0132] In some embodiments, the applied signal may decelerate or accelerate the primary charged particle beam toward the stage, modifying the focus of the primary charged particle beam incident on the wafer, based on the polarity of the signal.

[0133] Figure 7 is a flow chart illustrating an exemplary method of irradiating a sample with a charged particle beam using a charged particle beam system consistent with embodiments of the present disclosure. The method of observing the sample may be performed by Figure 3 Charged particle beam system 300 or Figure 1 It will be appreciated that the charged particle beam device may be controlled to direct the charged particle beam to the wafer (e.g., Figure 2 The wafer 203 or a region of interest on the wafer can be observed, imaged, and inspected. Imaging can include scanning the wafer to image at least a portion of the wafer, a pattern on the wafer, or the wafer itself. Inspecting the wafer can include scanning the wafer to inspect at least a portion of the wafer, a pattern on the wafer, or the wafer itself. Observing the wafer can include monitoring certain characteristics of the wafer or the region of interest on the wafer, such as the reproducibility or repeatability of the pattern.

[0134] In step 710, similar to steps 510 and 610, a primary charged particle beam (e.g., Figure 2 The primary charged particle beam 220 is generated from a charged particle source. The primary charged particle beam can be, for example, an electron beam generated from an electron source. The electron source can include, but is not limited to, the emission of thermionic electrons from a tungsten filament or a Lab6 cathode, or field emission of electrons from a tungsten / ZrO2 cold cathode.

[0135] In step 720, a height sensor (e.g., Figure 3 Height sensor 340) and laser interferometer ( Figure 3 A positioning sensing system such as a laser interferometer 350 may be used to determine the position of the platform (e.g., Figure 2-Figure 3 In some embodiments, the lateral and vertical displacements of the platform 201 (of the platform 201) can be determined. In some embodiments, one or more optical height sensors can be used to determine the vertical displacement, and one or more laser interferometers can be used to determine the lateral displacement of the platform. In some embodiments, during the scanning of the wafer 203 (set on the platform 201), the pitch effect compensation on the XY axis can require simultaneous and continuous compensation for the lateral displacement (XY axis) and the vertical displacement (Z axis). The vertical displacement can be compensated by adjusting the focus of the incident beam on the wafer 203 or by adjusting the positioning of the platform 201 on the Z axis. In some embodiments, the measured xy coordinates can be corrected based on the pitch effect from the X and Y axes. The corrected xy coordinates of the platform 201 may include the displacement caused by the pitch effect. The beam deflection controller 367, the beam control module 365 and the platform control module 362 can communicate with one or more laser interferometers to receive updated platform positioning information. Compensating for pitch effects in the x and y axes can include determining lateral beam corrections from the measured xy positioning coordinates while scanning, and continuously adjusting the focus of the primary charged particle beam incident on the wafer to compensate for vertical displacement. In some embodiments, a height sensor and a laser interferometer can be used to determine stage positioning, stage calibration, calibration of motors, and calibration of an actuator configured to move the stage in one of the X, Y, and Z axes.

[0136] In step 730, after determining the lateral displacement of the platform, the beam deflection controller (e.g., Figure 3 The beam deflection controller 367) may apply a first signal to the primary beam deflector (e.g., Figure 3 The deflector array 320 of FIG. 3 may be configured to deflect the primary charged particle beam in at least one of the X or Y axes. The applied signal may comprise an electrical signal having a high control bandwidth in the range of 10 kHz to 50 kHz. The deflected charged particle beam (e.g., Figure 3 The deflected charged particle beam 330) can at least partially compensate for the determined lateral displacement of the platform.

[0137] In step 740, after determining the vertical displacement of the platform, the beam deflection controller can apply a second signal to the platform to adjust the focus of the deflected charged particle beam on the Z axis. The applied second signal can include a voltage signal that is configured to decelerate or accelerate the charged particle beam toward the platform. The deceleration or acceleration voltage of the charged particle beam can correspond to the vertical displacement of the platform and can at least partially compensate for the vertical displacement by modifying the focus of the incident charged particle beam on the Z axis. The voltage signal can include a signal with a high control bandwidth in the range of 50 kHz to 200 kHz.

[0138] In step 750, the platform control module (e.g., Figure 3 The platform control module 362 of FIG. 360 may apply a signal to the platform motion controller (e.g., Figure 3 In some embodiments, the signal may include one or more signals to independently control the z motion controller (e.g., Figure 3 Actuators 372_1, 372_2 and 372_3) are used to adjust the Z leveling of the platform so that the platform is substantially perpendicular to the primary charged particle beam.

[0139] Inspection and imaging of three-dimensional (3D) structures (such as contact holes, vias, or interconnects on semiconductor chips) can be performed by positioning a reference sample and adjusting the depth of focus of probing charged particles (e.g., electrons in an electron beam inspection tool) (e.g., by adjusting the landing energy of the electrons on the sample to vary the depth of focus). One way to adjust the depth of focus or focal plane of the primary electron beam includes adjusting the magnetic field associated with the objective lens by adjusting the current through the magnetic objective lens coil. Adjusting the magnetic field to cause a change in the depth of focus can induce delays related to the response time between changing the current and adjusting the magnetic field, slowing the process and thereby negatively impacting inspection throughput.

[0140] Another of several ways to adjust the depth of focus or focal plane is to adjust the landing energy of the electrons of the electron beam, such as by adjusting the voltage of an anode (e.g., anode 216). Adjustment of the anode voltage can adjust the velocity or energy of the electrons incident on the sample surface, thereby adjusting the depth of focus, etc. However, although the depth of focus can be adjusted, the adjusted primary electron beam can be rotated with respect to one or more axes due to changes in the electromagnetic field experienced by the electrons as the beam travels downstream toward the sample. The rotation of the primary electron beam can cause the image formed thereby to be rotated, etc., negatively affecting inspection throughput. Therefore, it may be desirable to provide a method to adjust the focal plane of the incident primary electrons while maintaining a desired inspection throughput, such as by adjusting the landing energy of the primary electron beam to cause a desired change in the focal plane.

[0141] Now refer to Figure 8 , Figure 8 An exemplary charged particle beam system 800 consistent with embodiments of the present disclosure is illustrated. The charged particle beam system 800 may include: a cathode 802 (similar to Figure 2 a charged particle source configured to generate a charged particle beam (e.g., an electron beam) along a main optical axis 801; a source supply unit 805; a buncher lens 810 (similar to Figure 3 beam collector lens 315); electron detector 815 (similar to Figure 2 electronic detector 206); objective lens assembly 820 (similar to Figure 2 The charged particle beam system 800 may further include a control unit 830 configured to control electrical signals applied to the platform 860 and the objective lens assembly 820. Alternatively, the charged particle beam system 800 (such as an electron beam system) may be Figure 2 Imaging system 200 or Figure 1 It should be understood that, although not explicitly depicted, the charged particle beam system 800 may include other standard or non-standard components to perform functions including, but not limited to, beam focusing, beam deflection, electron detection, beam current limiting, and the like.

[0142] In some embodiments, the charged particle beam system 800 can be configured to generate and focus an electron beam on a wafer 850, etc. Focusing the electron beam can include adjusting the height of the wafer 850 so that the electron beam is focused on a desired plane of the wafer 850. It should be understood that because the wafer 850 is disposed on a platform 860, adjusting the height of the platform 860 will result in adjustment of the height of the wafer 850. One of the several ways to focus the electron beam on the wafer 850 can include using a combination of optical and mechanical techniques. For example, an optical component such as an optical height sensor is used to determine the height of the platform 860 or the wafer 850, and a mechanical component such as a piezoelectric transducer is configured to mechanically move the platform 860 based on the determined height. However, using purely optical mechanical techniques for focusing the electron beam can result in inaccurate determinations for certain applications (such as inspection of 3D NAND flash memory devices including vertically stacked structures). In this case, it may be desirable to use the electrical techniques discussed herein to further fine-tune the focus of the electron beam, for example to enhance imaging resolution.

[0143] The source supply unit 805 may be configured to supply electrical power to the charged particle source to generate a charged particle beam. In some embodiments, the source supply unit 805 may be configured to supply electrical power to the charged particle source to generate a charged particle beam. Figure 2 An electric field is generated between the anode 216 of the field emitter and the cathode 802 so that a charged particle beam can be emitted from the charged particle source. In some embodiments, the charged particle source may include a field emission source, wherein charged particles (such as electrons) are emitted from a field emission gun by placing the cathode at a large electric field gradient. The field emission source may appropriately utilize two anode plates or more. The first anode plate may be configured to cause extraction or emission of charged particles from the field emitter, and the second anode plate may be configured to cause acceleration of the extracted charged particles toward the wafer 850. The source supply unit 805 may be configured to determine and supply extraction and acceleration voltages. In some embodiments, the source supply unit 805 may be a beam control module (such as a Figure 3 A beam control module 365) or a system control module such as Figure 3 360) or is coupled to the system control module.

[0144] like Figure 8 As shown, the charged particle beam system 800 may include a buncher lens 810 (similar to Figure 3 The condenser lens 810 may be configured to focus the charged particle beam. In some embodiments, the current of the primary beam of the primary charged particle beam may be adjusted by varying the focusing power of the condenser lens 810.

[0145] The electron detector 815 of the charged particle beam system 800 is similar to Figure 2 The electron detector 815 may be similar to or substantially similar to the electron detector 206. For example, the electron detector 815 may detect secondary electrons emitted from the wafer when interacting with electrons of the primary electron beam and generate a signal associated with the intensity of the detected secondary electrons. The objective lens assembly 820 of the charged particle beam system 800 may be similar to or substantially similar to the electron detector 206. Figure 2 The objective lens assembly 820 may include a control electrode 824 similar to Figure 2The objective lens assembly 820 may include, but is not limited to, a beam focusing assembly configured to adjust the focus of the primary electron beam directed toward the wafer 850 and a field modulation assembly configured to adjust the electric field to which the primary electron beam may be exposed. In some embodiments, the field modulation assembly may include a control electrode 824. In some embodiments, the electrical excitation of the control electrode 824 may be adjusted by varying the voltage or current to adjust the generated electric field. The charged particle beam system 800 may also include a control unit 830 configured to control the voltage applied to the platform 860 and the objective lens assembly 820. In some embodiments, the control unit 830 may be configured to apply a voltage to the control electrode 824 of the objective lens assembly 820.

[0146] In the context of the present disclosure, optomechanical techniques for adjusting the focus of the electron beam refer to adjusting the height of the platform 860 using a combination of electromechanical and optical devices, including but not limited to piezoelectric transducers, piezoelectric actuators, lasers, interferometers, photodiodes, etc. In the context of the present disclosure, electrical techniques for adjusting the focus of the electron beam refer to adjusting the height of the platform 860 by applying electrical signals to control electrodes (e.g., Figure 8 824) to manipulate the electromagnetic field associated with the electron beam.

[0147] As described above, in electron beam inspection tools (such as SEMs), the accuracy of electron beam focusing achieved by purely optomechanical techniques may not be sufficient for certain applications, such as vertically stacked structures in IC chips. Errors and variability in electron beam focusing introduced by, at least due to inaccurate stage motion control or mechanical vibrations, can be expected to limit the use of mechanical techniques. On the other hand, electrical techniques can provide more precise adjustment of the focal plane of the electron beam incident on the sample by modifying the electric or magnetic field on the sample, and can provide a faster method for adjusting the focal plane.

[0148] Now refer to Figure 9A , Figure 9A FIGURE 8 illustrates a flow chart illustrating an exemplary method for focusing a charged particle beam on a sample using a charged particle beam system 800 consistent with an embodiment of the present disclosure. The method for focusing a sample may be performed by Figure 3 Charged particle beam system 300, Figure 8 The charged particle beam system 800 shown or Figure 1 It will be appreciated that the charged particle beam device may be controlled to direct the charged particle beam at a wafer (e.g., Figure 8The wafer 850) or a region of interest on the wafer is observed, imaged, and inspected. Imaging can include scanning the wafer to image at least a portion of the wafer, a pattern on the wafer, or the wafer itself. Inspecting the wafer can include scanning the wafer to inspect at least a portion of the wafer, a pattern on the wafer, or the wafer itself. Observing the wafer can include monitoring the wafer or a region of interest on the wafer for pattern reproducibility or repeatability.

[0149] In step 910A, similar to steps 510, 610, and 710, a primary charged particle beam (e.g., Figure 2 The primary charged particle beam 220 is generated from a charged particle source. Figure 8 The sample on the platform 860 is irradiated with a primary charged particle beam. In some embodiments, at least a portion of the sample can be irradiated with at least a portion of the primary charged particle beam. The primary charged particle beam can be, for example, an electron beam generated from an electron source. The electron source can include, but is not limited to, thermionic emission of electrons from a tungsten filament or Lab6 cathode, or field emission of electrons from a tungsten / ZrO2 cold cathode.

[0150] The sample can be placed directly on the platform. In some embodiments, the sample can be placed on an adapter, such as a sample holder, which is placed on the platform and fixed to the platform. The geometric centers of the sample, sample holder, and platform can be aligned with each other and with the principal optical axis (e.g., Figure 8 The sample, sample holder and platform can be aligned with the main optical axis 801 of the microscope. The sample, sample holder and platform can be arranged in a plane perpendicular to or substantially perpendicular to the main optical axis. In some embodiments, the sample or platform can be tilted off-axis so that the primary charged particle beam is incident on the sample at an angle less than or greater than 90 °. In some embodiments, the sample and platform can be mechanically coupled so that the displacement of the platform on any one of the X, Y or Z axes correspondingly causes the displacement of the sample. In some embodiments, the sample holder and platform can be electrically coupled so that there can be ohmic contact or an insignificant voltage potential gradient between them. In some embodiments, the sample and sample holder can be electrically coupled so that there can be ohmic contact or an insignificant potential potential gradient between them.

[0151] In step 920A, the position of the initial focus of the charged particle beam is adjusted using the first component, the reference sample. As used herein, the initial focus refers to the approximate point or approximate plane of focus of the charged particle beam. In some embodiments, adjusting the position of the initial focus may include using an optical height sensor (e.g., Figure 8The initial position of the platform on the Z axis is determined using a more accurate optical positioning sensing technology such as a height sensor 840 (e.g., a height sensor 840). Based on the determined initial position of the platform and the desired focal plane of the primary charged particle beam, the position of the platform is adjusted so that the initial focus of the primary charged particle beam is formed on or substantially close to the sample surface. In some embodiments, it may be desirable to form the initial focus on the top surface of the sample.

[0152] In some embodiments, the height sensor may include a laser diode assembly including a radiation platform or a sample disposed on the platform (eg, Figure 8 The height sensor can be connected to a platform control module (e.g., Figure 3 Platform control module 362), beam control module (eg, Figure 3 In some embodiments, the platform control module and the beam control module can communicate with each other to adjust the height of the platform to focus the primary charged particle beam on the sample.

[0153] In step 930A, after forming an initial focus on the sample in step 920A, the focus of the primary charged particle beam can be further adjusted by manipulating the electromagnetic field associated with the sample using a second component. The second component may include, but is not limited to, a control electrode of the objective lens (e.g., Figure 8 The second assembly may be located downstream of the focusing assembly of the objective lens. The electromagnetic field associated with the sample may include electric and magnetic fields that affect the sample. Manipulating the electromagnetic field may allow further adjustment of the initial focus of the charged particle beam to form a final focus on the sample. The electromagnetic field may be applied to the objective lens assembly (e.g., Figure 8 The control electrode (e.g., Figure 8 The charged particle beam may be manipulated by adjusting an electrical signal to a control electrode 824 ), adjusting an electrical signal to the platform, or adjusting a magnetic field configured to affect the characteristics of the charged particle beam.

[0154] In certain embodiments, manipulation of electromagnetic field can comprise adjusting the electric signal of the control electrode that is applied to object lens assembly.The initial focus of charged particle beam can be adjusted along the Z axis by the electrical excitation (for example, voltage) of adjusting control electrode.The initial height adjustment or initial focus of charged particle beam are realized by adjusting the height of platform based on optical measurement in step 920A.After forming initial focus, the electrical excitation of control electrode can be changed to adjust the path or the energy of charged particle beam, thereby adjustment focus.For example, changing the voltage signal that is applied to control electrode can manipulate the electric field that charged particle beam experiences, and therefore makes it possible to adjust the focus of charged particle beam on sample surface.The combination of optical machinery as described herein and electrical technology can enable the user to obtain high imaging quality and high resolution.

[0155] In some embodiments, manipulating the electromagnetic field can include adjusting an electrical signal applied to the platform. The initial focus of the charged particle beam can be adjusted along the Z-axis by adjusting a voltage signal applied to the platform. The voltage signal applied to the platform can adjust the landing energy of the charged particle beam on the sample surface. As used herein, the landing energy of the charged particle beam can be defined as the energy of the charged particle beam when it impacts the sample, and can be the difference between the acceleration voltage and the platform / sample bias voltage. In order to improve image resolution and contrast by adjusting the focus of the incident primary charged particle beam, the user can apply a beam-energy modification voltage to the platform to reduce or increase the beam energy of the incident charged particle beam on the sample.

[0156] In some embodiments, manipulating the electromagnetic field may include adjusting an electrical signal applied to the sample or wafer so that the charged particles are decelerated (lower landing energy) or accelerated (higher landing energy) before they impinge on the sample. For example, in an SEM, if the high voltage (the accelerating voltage applied to the column) is 12 kV (e.g., by Figure 2In one embodiment, the charged particle beam is a charged particle beam having a cathode 218 and anode 216 with a voltage set to -12 kV and ground, respectively, and a platform / sample bias voltage of -9 kV (relative to ground), the electrons are first accelerated to an energy of 12 keV in the column and then, after exiting the column, are decelerated by a 9 kV electric field such that the landing energy of the charged particles in the charged particle beam is 3 keV. Accelerating or decelerating the charged particles incident on the sample can change the penetration depth into the sample and can change the focal depth of the beam. At lower landing energies (e.g., less than 1 keV), the charged particle beam can primarily interact with the top surface of the sample. At higher landing energies (e.g., between 1 keV and 6 keV), the penetration depth can be greater, thereby providing information from the sample population. In some embodiments, the landing energy of the charged particle beam is in the range of 250 eV to 6 keV. While lower landing energies can avoid bulk analysis, the signal intensity of the generated secondary charged particles can be lower, thereby negatively impacting the ability to analyze the sample. On the other hand, higher landing energies may be required to extract volume and sub-surface information, but they may charge the sample, thereby negatively impacting the ability to analyze the sample. In some embodiments, the landing energy of the charged particle beam is in the range of 500 eV to 3 keV, depending on the sample, any requirements, and the application involved.

[0157] Adjusting the landing energy of the charged particle beam can include applying one or more electrical signals to the platform. In some embodiments, the electrical signal can include a first component of a voltage signal or a second component of the voltage signal. The first component of the voltage signal can be a voltage applied to the platform or sample to affect the acceleration of the charged particle beam. For some applications, for example, the focus of the charged particle beam at the initial focus on the sample may be insufficient, and therefore the charged particle beam can be further focused or adjusted to achieve better resolution or contrast. In some embodiments, the first component of the voltage signal can be configured to coarsely adjust the initial focus of the charged particle beam on the sample surface. As used herein, coarse adjustment of the initial focus can refer to adjusting the focus along the Z axis. In some embodiments, the first component of the voltage signal can include a voltage signal in the range of 5kV to 10kV.

[0158] The second component of the voltage signal can be a voltage applied to the platform or sample to fine-tune the initial focus formed by adjusting the positioning of the platform on the Z axis. As used herein, fine-tuning of the initial focus can refer to adjustment of the focus along the Z axis to achieve a sharp focus. The second component of the voltage signal can deflect the incident charged particle beam, allowing smaller positioning adjustments along the X, Y or Z axis to achieve a sharper focus. In some embodiments, the second component of the voltage signal can include a voltage signal in the range of -150V to +150V. It should be understood that based on factors including but not limited to application, sample and tool conditions, the first component or the second component of the applied voltage signal can be above or below the ranges mentioned herein.

[0159] In some embodiments, the landing energy of a charged particle beam incident on a sample surface can be adjusted by manipulating an electromagnetic field by applying a single electrical signal. The single electrical signal can include a first component and a second component of a voltage signal. For example, if the first component of the voltage signal for coarse focus adjustment is -9 kV and the second component of the voltage signal for fine focus adjustment is -100 V, the single electrical signal will include a voltage signal of -9.1 kV. Alternatively, if the first component of the voltage signal for coarse focus adjustment is -9 kV and the second component of the voltage signal for fine focus adjustment is +100 V, the single electrical signal will include a voltage signal of -8.9 kV.

[0160] In some embodiments, manipulating the electromagnetic field associated with the sample can include adjusting the magnetic field associated with the sample. In some embodiments, adjusting the electric field by applying an electrical signal can result in adjustment of the magnetic field. Adjustment of the magnetic field by an electrical or magnetic component can affect the characteristics of the charged particle beam. For example, current passing through an electromagnetic lens coil creates a magnetic field in the aperture of a pole piece, and the pole piece can be used to converge the charged particle beam. In some embodiments, the characteristics of the charged particle beam can include, but are not limited to, the path, direction, velocity, or acceleration of the charged particle beam.

[0161] Now refer to Figure 9B , Figure 9B An exemplary method of focusing a charged particle beam on a sample using a charged particle beam system 800 is illustrated, consistent with an embodiment of the present disclosure. The method of focusing a sample may be performed by Figure 3 Charged particle beam system 300, Figure 8 Charged particle beam system 800 or Figure 1 The EBI system 100 is used to perform.

[0162] In step 910b, similar to steps 510, 610, 710, and 910a, the primary charged particle beam (e.g., Figure 2 The primary charged particle beam 220 is generated from a charged particle source. Figure 8The sample on the platform 860) is irradiated using a primary charged particle beam. In some embodiments, at least a portion of the sample can be irradiated using at least a portion of the primary charged particle beam. The primary charged particle beam can be, for example, an electron beam generated from an electron source. The electron source can include, but is not limited to, thermionic emission of electrons from a tungsten filament or Lab6 cathode, or field emission of electrons from a tungsten / ZrO2 cold cathode.

[0163] The sample can be placed directly on the platform. In some embodiments, the sample can be placed on an adapter, such as a sample holder, which is placed on the platform and fixed to the platform. The geometric centers of the sample, sample holder, and platform can be aligned with each other and with the principal optical axis (e.g., Figure 8 The sample, sample holder, and platform can be aligned with the principal optical axis 801 of the sample. The sample, sample holder, and platform can be arranged in a plane perpendicular to or substantially perpendicular to the principal optical axis. In some embodiments, the sample or platform can be tilted off-axis so that the primary charged particle beam is incident on the sample at an angle less than or greater than 90°. In some embodiments, the sample and platform can be mechanically coupled so that displacement of the platform on any one of the X, Y, or Z axes correspondingly causes displacement of the sample. In some embodiments, the sample holder and platform can be electrically coupled so that there can be ohmic contact or an insignificant voltage potential gradient between them.

[0164] In step 920B, similar to step 920A, the position of the initial focus of the charged particle beam is adjusted using the first component, the reference sample. As used herein, the initial focus refers to the approximate point or approximate focal plane of the charged particle beam. In some embodiments, adjusting the position of the initial focus may include using an optical height sensor (e.g., Figure 8 The initial position of the platform on the Z axis is determined using a more accurate optical positioning sensing technology such as a height sensor 840 (e.g., a height sensor 840). Based on the determined initial position of the platform and the desired focal plane of the primary charged particle beam, the positioning of the platform is adjusted so that the initial focus of the primary charged particle beam is formed on or substantially close to the sample surface. In some embodiments, it may be desirable to form the initial focus on the top surface of the sample.

[0165] In some embodiments, the height sensor may include a laser diode assembly including a radiation platform or a sample disposed on the platform (eg, Figure 8 The height sensor can be connected to a platform control module (e.g., Figure 3 Platform control module 362), beam control module (eg, Figure 3In some embodiments, the platform control module and the beam control module can communicate with each other to adjust the height of the platform to focus the primary charged particle beam on the sample.

[0166] In step 930B, after forming an initial focus on the sample in step 920B, an electromagnetic field may be applied to the objective lens (e.g., Figure 8 Objective lens assembly 820 or Figure 2 of 204) of the control electrode (eg, Figure 8 The control electrode 824 or Figure 2 In step 920b, the electric signal of control electrode is controlled to form the final focus. The initial focus of charged particle beam can be adjusted to form the final focus along the Z axis by adjusting the electric excitation of control electrode. The initial height adjustment or initial focus of charged particle beam are realized by the height based on optical measurement adjustment platform in step 920b. After forming the initial focus, the electric excitation of control electrode can be changed to adjust the path or the energy of charged particle beam, thereby adjusting the focus. For example, changing the voltage signal applied to control electrode can manipulate the electric field that charged particle beam experiences, and therefore realizes the adjustment of the focus of charged particle beam on the sample surface. The combination of optical machinery and electric technology as described herein can enable the user to obtain high imaging resolution.

[0167] As mentioned above, one of the challenges encountered during inspection of IC chips with device architectures that include vertically stacked components is insufficient imaging range and resolution. For example, measuring the depth of a 4-5 μm deep metal contact hole or detecting buried defect particles at the base of a structure can be used to analyze defects and develop process conditions based on information extracted from imaging and accurate measurements. The large depth of focus (DOF) of a charged particle beam system (such as a SEM) can achieve a larger imaging range, so that the top surface, bottom surface, and intermediate layers of deep features can be imaged simultaneously and in real time while maintaining high imaging resolution.

[0168] Using existing techniques to inspect vertically stacked structures, such as 3D NAND flash memory devices, can provide limited or inaccurate information, both of which can negatively impact the yield and quality of the devices produced. Therefore, it would be desirable to enable existing inspection tools to have real-time 3D imaging capabilities, thereby improving the imaging range while maintaining high imaging resolution. The ability to adjust the focus of a charged particle beam along the z-axis by manipulating electromagnetic fields can be used to image multiple planes, features, or regions of interest within a sample, thereby enabling accurate 3D morphology to be obtained.

[0169] Now refer to Figure 10 , Figure 10is a schematic diagram illustrating a charged particle beam system 1000 including an electron beam inspection tool 1004 consistent with an embodiment of the present disclosure. Figure 10 As shown, the charged particle beam system 1000 may include Figure 1 The apparatus includes an electron beam inspection tool 1004 similar to the electron beam tool 104, a controller 1009 electrically or electronically connected to the electron beam inspection tool 1004, and an image acquisition system 1060 including a data processor. It should be understood that although the image acquisition system 1060 is shown as being external to the controller 1009, it can be part of the controller 1009.

[0170] In some embodiments, the charged particle beam system 1000 can provide mechanisms to support multiple operating modes. For example, the charged particle beam system 1000 can be configured to operate in a 2D imaging mode to obtain a high-resolution planar image of a sample or region of interest, or in a 3D imaging mode to obtain a high-resolution morphological image of the sample, wherein the high-resolution morphological image contains features and structures having a 3D shape. In some embodiments, the charged particle beam system 1000 can be configured to switch between modes within an inspection scan based on the desired analysis, the sample being analyzed, or the application. For example, the charged particle beam system 1000 can first perform an inspection of the region of interest in a 2D imaging mode, which generally provides higher throughput than a 3D imaging mode, and then switch to a 3D imaging mode to perform a high-resolution scan of, for example, a detected defect. This can eliminate the need for two tools, thereby improving the overall throughput of the inspection process. In some embodiments, the charged particle beam system 1000 can perform an inspection scan only in a 3D imaging mode to obtain a high-resolution scan of a region of interest previously determined by a user.

[0171] In some embodiments, the controller 1009 may include a computer or processor configured to perform various controls of the electron beam inspection tool 1004. The controller 1009 may be electronically connected to the electron beam inspection tool 1004 and may include processing circuitry configured to perform various signal and image processing functions and generate various control signals to control the operation of the charged particle beam system 1000. In some embodiments, the controller 1009 may be configured to switch between operating modes based on user input. Switching operating modes may include, but is not limited to, activating hardware components, executing software programs, and the like. For example, switching the electron beam inspection tool 1004 to a 3D imaging mode may include adjusting a voltage signal applied to the platform, adjusting a voltage signal applied to an objective lens (e.g., Figure 8 The control electrode (e.g., Figure 8The controller 1009 may be configured to generate a voltage signal to the control electrode 824 of the controller 1009, move the stage in the X, Y, or Z axis to adjust the focus of the charged particle beam, instruct the image acquisition system 1060 to acquire an image of the sample at the focus, execute an algorithm to process the image information, etc. Although the image acquisition system 1060 is shown as being external to the controller 1009, it may be part of the controller 1009.

[0172] Image acquisition system 1060 may be substantially similar to Figure 2 The image acquirer 260 can perform the Figure 2 The image acquisition system 1060 may be configured to acquire images or image frames and may include one or more processors (not shown) configured to perform functions related to imaging or post-processing and one or more storage units (not shown) configured to store acquired image frames, post-processing information, analysis results, etc. The image acquisition system 1060 may be configured to communicate with the controller 1009. For example, upon determining that a desired focus is achieved, the controller 1009 may cause the image acquisition system 1060 to acquire one or more image frames at that focus. The image acquisition system 1060 may be operated by the controller 1009 or by a user. In some embodiments, the image acquisition system 1060 may be remotely operated by a computer-implemented program such as software, an algorithm, or a set of instructions.

[0173] As previously mentioned, the focusing achieved using optomechanical techniques may be insufficient for high-resolution and wide-range imaging in some applications, and therefore a more precise and larger depth of focus is required. A larger depth of focus can allow high-resolution imaging of deep 3D features, so that the top and bottom surfaces of the features can be imaged simultaneously and clearly. Discussed herein is an exemplary method for focusing a charged particle beam on a sample surface using a 3D imaging mode of operation of the charged particle beam system 1000. It should be understood that the number and order of the steps in the focusing method are merely exemplary and are for illustrative purposes only. Steps may be added, deleted, edited, reordered, and omitted as needed. The 3D imaging mode of operation includes using a combination of optomechanical and electrical techniques to achieve focusing of the charged particle beam on multiple focal planes of the sample, thereby allowing the user to clearly image the 3D features as a whole.

[0174] In 3D imaging mode, the charged particle beam system 1000 can be configured to use optomechanical techniques to perform platform (e.g., Figure 8An initial height adjustment of the platform 860 is performed so that the focus of the charged particle beam coincides or substantially coincides with a desired focal plane of the wafer 850 disposed on the platform 860. In some embodiments, the initial height adjustment of the platform 860 can be performed in a 2D imaging mode, and once the height of the platform 860 is adjusted in the 2D imaging mode using the optical height sensor and the piezoelectric motor, the charged particle beam system 1000 can be switched to operate in a 3D imaging mode.

[0175] Once the initial height adjustment is achieved, the controller (e.g. Figure 10 The controller 1009 of the electron beam inspection tool 1004 can cause the electron beam inspection tool 1004 to adjust the initial focus of the charged particle beam by manipulating the electromagnetic field associated with the sample. The electromagnetic field can be manipulated to adjust the focal plane of the charged particle beam along the Z axis, allowing the charged particle beam to be focused at multiple focal planes of the sample and thus providing more accurate 3D morphological information. The electromagnetic field associated with the sample can be manipulated by adjusting the landing energy of the charged particles on the sample, adjusting the electrical excitation of the control electrode of the objective lens, or adjusting the stage bias voltage.

[0176] In some embodiments, manipulating the electromagnetic field by adjusting the landing energy can include applying a first component of a voltage signal to coarsely adjust the initial focus of the charged particle beam on the sample surface, and applying a second component of the voltage signal to the platform to fine-tune the initial focus of the charged particle beam on the sample surface. The first component of the voltage signal can be determined based on the desired height adjustment to move the focal plane a predetermined distance along the Z axis. The landing energy can be varied based on an acceleration voltage applied to accelerate the charged particles toward the sample and the first component of the voltage signal applied to the platform. The second component of the voltage signal can be applied to further fine-tune the focus along the Z axis. The voltage signal can be applied to, for example, a control electrode of the objective lens (e.g., Figure 8 control electrode 824), a platform (e.g., Figure 8 platform 860) or other optomechanical components configured to affect the electromagnetic fields of the system.

[0177] After the charged particle beam is focused using electrical techniques, the controller 1009 can instruct the image acquisition system 1060 to acquire one or more image frames of the feature or structure. The acquired image frames can be stored and accessed for analysis by the user. In some embodiments, the stored image frames and corresponding focal plane information can be used to reconstruct a 3D image of the structure using, for example, a reconstruction algorithm.

[0178] Now refer to Figures 11A-11F , illustrates an image frame and corresponding focal plane of a feature on a sample consistent with an embodiment of the present disclosure. Figure 11A 、 Figure 11C and Figure 11Erepresents the top, middle, and bottom focal planes, respectively, in a cross-sectional view of a feature such as a metal contact hole, and Figure 11B 、 Figure 11D and Figure 11F The SEM image corresponding to the focal plane is shown. It should be understood that other features including but not limited to interconnects, metal pads, photoresist profiles, etc. can also be imaged.

[0179] In the sample (e.g. Figure 8 The exemplary features 1110 on the wafer 850) may include metal contact holes, for example, in a 3D NAND flash memory device. In some embodiments, the features 1110 may have a conical, cylindrical, triangular, or rectangular shape, and a circular or elliptical cross-section. Figure 11A As shown in the cross-sectional view of FIG. 1 , for example, feature 1110 may include a tapered metal contact hole having a height H1, a top diameter d1 along a top plane 1115, and a diameter d2 along a mid-plane (eg, Figure 11C The middle diameter d3 of the middle plane 1135) and the middle diameter d3 along the base plane (e.g., Figure 11E 1155). In some embodiments, height h1, top diameter d1, and base diameter d5 may comprise the critical dimensions of feature 1110. As used herein, a critical dimension of a feature or device may refer to a dimension that can affect the electrical performance of the device, as the critical dimension may contribute to parasitic capacitance and resistance. One of ordinary skill in the art will understand that a critical dimension is a dimension that can be adjusted to optimize device performance and manufacturing yield.

[0180] Figure 11B An image frame 1150 (eg, a SEM image) of an array of features 1110 is shown, imaged using a focusing method using a combination of optomechanical and electrical techniques discussed above. Figure 11B The focal plane of the charged particle beam in is adjusted to coincide with the top plane 1115 of feature 1110. It should be understood that each feature 1110 of the array can have different sizes (including height h1) and the focal plane of the charged particle beam may not coincide with the top planes of other features of the array. In such a case, the controller 1009 can be configured to adjust the focal plane of the charged particle beam based on the feature 1110 under investigation and its size.

[0181] Now refer to Figure 11C and Figure 11D , respectively, illustrate a schematic diagram of a feature 1110 having a mid-plane 1135 and a corresponding image frame 1152. Although the mid-plane 1135 is shown as being located between the top plane 1115 and the base plane (e.g., Figure 11E It should be understood that although the top plane 1115 and the base plane 1155 are located at the center of the Z axis, it can be any plane between the top plane 1115 and the base plane 1155 and perpendicular to the Z axis. Figures 11A-11F Three planes and corresponding image frames are shown, but any number of planes may be imaged as appropriate. In some embodiments, one or more image frames may represent a plane of feature 1110. For example, image acquisition system 1060 may acquire more than one image frame of a plane as desired.

[0182] Figure 11E and Figure 11F Schematic diagrams of a feature 1110 having a base plane 1155 and a corresponding image frame 1154 are shown, respectively. As an example, the feature 1110 is shown as having a tapered shape with a diameter gradually tapering along its height H1. In this case, as shown in FIG. Figure 11A 、 Figure 11C and Figure 11E As shown, the diameter of the top plane of the feature 1110 (eg, d1) can be greater than the middle diameter d3, and the middle diameter d3 can be greater than the base diameter D5 of the feature 1110 (D1>D3>D5). Figure 11B 、 Figure 11D and Figure 11F In image frames 1150, 1152, and 1154 of FIG. 1 , the dark circular area highlighted by the dashed line depicts a plan view of the in-focus plane of feature 1110. The diffuse, lighter areas surrounding the dark area within the dashed line represent out-of-focus layers of the sample. It should be understood that the dashed line highlighting the in-focus plane provides a visual aid and is for illustration purposes only.

[0183] Now refer to Figure 12 , Figure 12 1 is a schematic diagram of a process 1200 for generating a 3D image reconstructed from image frames captured at multiple focal planes consistent with an embodiment of the present disclosure. For example, feature 1210 may include a tapered metal contact hole tapering along a height h1 such that a top diameter d1 is greater than a base diameter d5. Figure 12 12. As shown, top plane 1215 represents the top surface of feature 1210 having a top diameter d1 as shown in corresponding top view 1217. Middle planes 1225, 1235, and 1245 represent middle planes of feature 1210 having diameters d2, d3, and d4, respectively, as shown in corresponding top views 1227, 1237, and 1247. Base plane 1255 represents the bottom surface of feature 1210 having a base diameter d5, as shown in corresponding top view 1257. Image frames 1220, 1230, 1240, 1250, and 1260 can be reconstructed to generate a 3D image 1270 of feature 1210.

[0184] In some embodiments, in a 3D imaging mode, the charged particle beam can be focused on the top surface of the feature 1210 so that the focal plane of the charged particle beam can coincide with the top plane 1215 of the feature 1210. The focal plane that coincides with the top plane 1215 can also be referred to as a first focal plane. The image acquisition system 1060 can be configured to acquire a first image frame 1220 of the top surface of the feature 1210. The charged particle beam can be focused by first adjusting the height of the platform 860 to form an initial focus of the charged particle beam on the sample through optical mechanical components, and then adjusting the initial focus through electrical components (including but not limited to adjusting the landing energy of the charged particles, adjusting the electrical excitation of the control electrode, or adjusting the platform bias voltage). In some embodiments, the image acquisition system 1060 can acquire more than one image frame at the focal plane. The acquired image frames can be stored in a storage medium (e.g., Figure 2 The image acquisition system 1060 may be coupled to a storage device 270, such as a hard disk, random access memory (RAM), or other computer-readable memory. The storage medium may be coupled to the image acquisition system 1060 and may be used to store scanned raw image data as raw images and post-processed images. Information associated with the focal plane, acquisition conditions, tool parameters, and the like may also be stored in the storage medium.

[0185] The focus of the charged particle beam can then be adjusted to focus on a second focal plane located a certain distance below the first focal plane. In the context of this disclosure, "below" the first focal plane refers to a position deeper into the sample. The distance between the first and second focal planes can be predetermined by the user based on the application or requirements. In some embodiments, the distance can be dynamically adjusted based on the material of the feature or sample being imaged. The image acquisition system 1060 can be configured to acquire a second image frame 1230 of the feature 1210 at a deeper intermediate plane 1225. The focal plane of the charged particle beam can be shifted deeper into the sample by manipulating the electric field, magnetic field, or both. For example, the landing energy of the charged particles can be adjusted to form a focal plane below the top surface of the sample. In some embodiments, the position of the focal plane can be shifted by adjusting the voltage applied to the control electrode of the objective lens. Adjusting the voltage applied to the control electrode can manipulate the electromagnetic field associated with the sample and affect the path of the charged particles incident on the sample. For example, the charged particles can be accelerated, decelerated, deflected, filtered, or focused based on the electrical excitation and the applied voltage signal. The image acquisition system 1060 may be configured to acquire a third image frame 1240 at the intermediate plane 1235, a fourth image frame 1250 at the intermediate plane 1245, and a fifth image frame 1260 at the base plane 1255. Figure 12Five imaging planes are illustrated as being used to reconstruct the 3D image, but any number of imaging planes that allows coverage of the depth of the feature being imaged may be used to accurately reconstruct the feature.

[0186] In some embodiments, image frames 1220, 1230, 1240, 1250, and 1260 may be reconstructed to generate a 3D image 1270 of feature 1210. In some embodiments, at least two image frames and associated focal plane information may be used, for example, to generate 3D image 1270 of feature 1210, extract key size information, determine overlay shift, etc. The image frames may be reconstructed using a computer-implemented 3D reconstruction algorithm, software program, image processing program, etc.

[0187] Now refer to Figure 13 , Figure 13 The diagram illustrates a flow chart showing an exemplary method for generating a 3D image of a sample in a charged particle beam system consistent with an embodiment of the present disclosure. The method for generating a 3D image of a sample can be respectively Figure 1 The live EBI system 100, Figure 2 Imaging system 200, Figure 3 、 Figure 8 and Figure 10 The method is performed using the charged particle beam system 300, 800 or 1000.

[0188] In step 1310, similar to steps 510, 610, 710, and 910A, a primary charged particle beam (e.g., Figure 2 The primary charged particle beam 220 is generated from a charged particle source. Figure 8 The sample on the platform 860 is irradiated with a primary charged particle beam. In some embodiments, at least a portion of the sample can be irradiated with at least a portion of the primary charged particle beam. The primary charged particle beam can be, for example, an electron beam generated from an electron source. The electron source can include, but is not limited to, thermionic emission of electrons from a tungsten filament or Lab6 cathode, or field emission of electrons from a tungsten / ZrO2 cold cathode.

[0189] The sample can be placed directly on the platform. In some embodiments, the sample can be placed on an adapter, such as a sample holder, which is placed on the platform and fixed to the platform. The geometric centers of the sample, sample holder, and platform can be aligned with each other and with the principal optical axis (e.g., Figure 8The sample, sample holder and platform can be aligned with the principal optical axis 801 of the microscope. The sample, sample holder and platform can be arranged in a plane perpendicular to or substantially perpendicular to the principal optical axis. In some embodiments, the sample or platform can be tilted off-axis so that the primary charged particle beam is incident on the sample at an angle less than or greater than 90 °. In some embodiments, the sample and platform can be mechanically coupled so that the displacement of the platform on any one of the X, Y or Z axes correspondingly causes the displacement of the sample. In some embodiments, the sample holder and platform can be electrically coupled so that there can be ohmic contact or an insignificant voltage potential gradient between them. In some embodiments, the sample and sample holder can be electrically coupled so that there can be ohmic contact or an insignificant voltage potential gradient between them.

[0190] In step 1320, the focus of the primary charged particle beam can be further adjusted by manipulating the electromagnetic field associated with the sample. Before adjusting the focus, the position of the platform on the Z axis is adjusted to form an initial focus of the primary charged particle beam at or substantially at the sample surface. As used herein, the initial focus refers to an approximate point or approximate focal plane of the charged particle beam. In some embodiments, adjusting the positioning of the platform may include using an optical height sensor (e.g., Figure 8 The initial position of the platform on the Z axis is determined using precise optical positioning sensing technology of a height sensor 840 (e.g., a height sensor 840). Based on the determined initial position of the platform and the desired focal plane of the primary charged particle beam, the positioning of the platform is adjusted so that the initial focus of the primary charged particle beam is formed on or substantially close to the sample surface. In some embodiments, it may be desirable to form the initial focus on the top surface of the sample.

[0191] In some embodiments, the height sensor may include a laser diode assembly including a radiation platform or a sample disposed on the platform (eg, Figure 8 The height sensor can be connected to a platform control module (e.g., Figure 3 Platform control module 362), beam control module (eg, Figure 3 In some embodiments, the platform control module and the beam control module can communicate with each other to adjust the height of the platform to focus the primary charged particle beam on the sample.

[0192] The electromagnetic field associated with the sample may include electric and magnetic fields that affect the sample. Manipulating the electromagnetic field may allow further adjustment of the initial focus of the charged particle beam to form a final focus on the sample. The electromagnetic field may be applied to the objective lens assembly (e.g., Figure 8 The control electrode (e.g., Figure 8 The charged particle beam may be manipulated by adjusting an electrical signal to a control electrode 824 ), adjusting an electrical signal to the platform, or adjusting a magnetic field configured to affect the characteristics of the charged particle beam.

[0193] In certain embodiments, manipulation of electromagnetic field can comprise adjusting the electric signal of the control electrode that is applied to objective lens assembly.The initial focus of charged particle beam can be adjusted along the Z axis by the electric excitation of adjusting control electrode.The initial height adjustment or initial focus of charged particle beam are realized by the height based on optical measurement adjustment platform.After forming initial focus, the electric excitation of control electrode can be changed to adjust the path or the energy of charged particle beam, thereby adjusting focus.For example, changing the voltage signal that is applied to control electrode can manipulate the electric field that charged particle beam experiences, and therefore realizes the adjustment of the focus of charged particle beam on sample surface.The combination of optical mechanics and electrical technology as described herein can enable the user to obtain high imaging resolution.

[0194] In some embodiments, manipulating the electromagnetic field can include adjusting an electrical signal applied to the platform. The initial focus of the charged particle beam can be adjusted along the Z-axis by adjusting a voltage signal applied to the platform. The voltage signal applied to the platform can adjust the landing energy of the charged particle beam on the sample surface. As used herein, the landing energy of the charged particle beam can be defined as the energy of the charged particle beam when it impacts the sample, and can be the difference between the acceleration voltage and the platform / sample bias voltage. In order to improve image resolution and contrast by adjusting the focus of the incident primary charged particle beam, the user can apply a beam-energy modification voltage to the platform to reduce or increase the beam energy of the charged particle beam incident on the sample.

[0195] In some embodiments, voltages can be applied to the platform or sample to decelerate (lower landing energy) or accelerate (higher landing energy) the charged particles before they impact the sample. For example, in an SEM, if the high voltage (the accelerating voltage applied to the column) is 12 kV and the platform / sample bias voltage is -9 kV, the electrons are first accelerated to an energy of 12 keV in the column and then, after exiting the column, are decelerated by a 9 keV electric field, resulting in an effective high voltage of 3 kV for the incident charged particle beam and a landing energy of 3 keV for the charged particles in the charged particle beam. Accelerating or decelerating the charged particles incident on the sample can alter the penetration depth into the sample. At lower landing energies (e.g., less than 1 keV), the charged particle beam can primarily interact with the top surface of the sample. At higher landing energies (e.g., between 1 keV and 6 keV), the penetration depth can be greater, thereby providing information from the sample population. In some embodiments, the landing energy of the charged particle beam ranges from 250 eV to 6 keV. While lower landing energies can avoid bulk analysis, the signal strength of the generated secondary charged particles may be lower, negatively impacting the ability to analyze the sample. On the other hand, higher landing energies may be required to extract bulk and sub-surface information, but this may charge the sample, negatively impacting the ability to analyze the sample. In some embodiments, the landing energy of the charged particle beam is in the range of 500 eV to 3 keV, depending on the sample, requirements, and application.

[0196] Adjusting the landing energy of the charged particle beam may include applying one or more electrical signals to the platform. In some embodiments, the electrical signal may include a first component and a second component of a voltage signal. The first component of the voltage signal may be a voltage applied to the platform or sample to affect the acceleration of the charged particle beam and thereby adjust the initial focus formed by adjusting the position of the platform on the Z-axis. For some applications, for example, the focus of the charged particle beam at the initial focus on the sample may be insufficient, and therefore the charged particle beam may be further focused or adjusted to achieve better resolution or contrast. In some embodiments, the first component of the voltage signal may be configured to coarsely adjust the initial focus of the charged particle beam on the sample surface. As used herein, coarse adjustment of the initial focus may refer to adjusting the focus along the Z-axis. In some embodiments, the first voltage signal may include a voltage signal in the range of 5kV to 10kV.

[0197] The second component of the voltage signal can be a voltage applied to the platform or sample to fine-tune the initial focus formed by adjusting the positioning of the platform on the Z axis. As used herein, fine-tuning of the initial focus can refer to adjustment of the focus along the Z axis to achieve a sharp focus. The second component of the voltage signal can deflect the incident charged particle beam, thereby allowing smaller positioning adjustments along the X, Y or Z axis to achieve a sharper focus. In some embodiments, the second component of the voltage signal can include a voltage signal in the range of -150V to +150V. It should be understood that based on factors including but not limited to application, sample and tool conditions, the first component or the second component of the applied voltage signal can be higher or lower than the range mentioned herein.

[0198] In some embodiments, the landing energy of a charged particle beam incident on a sample surface can be adjusted by manipulating the electromagnetic field by applying a single electrical signal. In some embodiments, the electrical signal can be applied by a single source. The electrical signal can include a voltage signal having one or more components. For example, if the first component of the voltage signal for coarse focus adjustment is -9 kV and the second component of the voltage signal for fine focus adjustment is -100 V, the electrical signal will include a voltage signal of -9.1 kV. Alternatively, if the first component of the voltage signal for coarse focus adjustment is -9 kV and the second component of the voltage signal for fine focus adjustment is +100 V, the electrical signal will include a voltage signal of -8.9 kV. In some embodiments, the first component and the second component of the voltage signal can include a coarse signal and a fine signal, respectively, and the electrical signal can be the sum of the first and second components of the voltage signal. It should be understood that the electrical signal can include two or more components as needed.

[0199] In some embodiments, manipulating the electromagnetic field associated with the sample can include adjusting the magnetic field associated with the sample. In some embodiments, adjusting the electric field by applying an electrical signal can result in adjustment of the magnetic field. Adjustment of the magnetic field by an electrical or magnetic component can affect the characteristics of the charged particle beam. For example, current passing through an electromagnetic lens coil creates a magnetic field in the aperture of a pole piece, and the pole piece can be used to converge the charged particle beam. In some embodiments, the characteristics of the charged particle beam can include, but are not limited to, the path, direction, velocity, or acceleration of the charged particle beam. In some embodiments, adjusting the magnetic field using a magnet can result in adjustment of the magnetic field. It should be understood that any type of magnet can be used to adjust the magnetic field as needed.

[0200] In step 1330, multiple focal planes can be formed based on the manipulation of the electromagnetic field. In a 3D imaging mode, a charged particle beam can be focused on a feature (e.g., Figure 12 1210) such that the focal plane of the charged particle beam can be aligned with the top plane of the feature (e.g., Figure 12The focal plane that coincides with the top plane may also be referred to as the first focal plane. Figure 10 The image acquisition system 1060 can be configured to acquire a first image frame of the top surface of the feature (e.g., Figure 12 The charged particle beam can be focused by, for example, adjusting the height of the platform to form an initial focus of the charged particle beam on the sample through optical mechanical components, and adjusting the initial focus through electrical components (including but not limited to adjusting the landing energy of the charged particles, adjusting the electrical excitation of the control electrodes, or adjusting the platform bias voltage).

[0201] The focus of the charged particle beam can then be adjusted to focus on a second focal plane located a distance below the first focal plane (e.g., Figure 12 The distance between the first and second focal planes can be predetermined by the user based on the application or requirements. In some embodiments, the distance can be dynamically adjusted based on the material of the feature or sample being imaged. The image acquisition system can be configured to focus on a deeper intermediate plane (e.g., Figure 12 A second image frame of the feature is acquired at the middle plane 1225 of the objective lens. The focal plane of the charged particle beam can be shifted deeper into the sample by manipulating the electric field or the magnetic field, or both. In some embodiments, the position of the focal plane can be shifted by adjusting the voltage applied to the control electrode of the objective lens. Adjusting the voltage applied to the control electrode can manipulate the electromagnetic field associated with the sample and affect the path of the charged particles incident on the sample. For example, the charged particles can be accelerated, decelerated, deflected, filtered, or focused based on the electrical excitation and the applied voltage signal. Multiple focal planes (e.g., Figure 12 The intermediate planes 1225, 1235, 1245 and 1255) can thus be formed based on the manipulation of the electromagnetic field. It should be understood that the number of intermediate focal planes can be adjusted as needed.

[0202] In step 1340, the image acquisition system may generate more than one image frame at the focal plane. In some embodiments, the image acquisition system may generate one image frame corresponding to the focal plane. The image acquisition system may be configured to communicate with a controller (e.g., Figure 10The controller 1009 communicates with the image acquisition system. For example, after determining that the desired focus has been achieved, the controller can cause the image acquisition system to acquire one or more image frames at that focus. The image acquisition system can be operated by the controller or by a user. In some embodiments, the image acquisition system can be remotely operated using a computer-implemented program such as software, an algorithm, or a set of instructions. The acquired image frames can be stored in a storage medium and can be used to save the scanned raw image data as a raw image and save a post-processed image. Information associated with the focal plane, acquisition conditions, tool parameters, etc. can also be stored in the storage medium.

[0203] In step 1350, the image frames acquired by the image acquisition system and the corresponding focal plane information may be reconstructed to generate a 3D image (eg, Figure 12 3D image 1270). In some embodiments, at least two image frames and associated focal plane information can be used, for example, to generate a 3D image of a feature, extract key size information, determine overlay shift, etc. The image frames 3D can be reconstructed using a computer-implemented reconstruction algorithm, software program, image processing program, etc.

[0204] The high throughput inspection of the wafer in production facilities (such as wafer factory) may require the platform of SEM equipment to move quickly and accurately in the repetitive pattern of start-stop motion.The start-stop motion can comprise the circulation of a plurality of high accelerations, high decelerations and sudden stops of platform, with the order of magnitude displacement of several microns or nanometers.Can cause the vibration generated owing to system dynamics with high speed and high acceleration mobile platform, vibration can in turn cause dynamic resonance in system, for example, vibration wave constructively interferes to cause the higher amplitude vibration of whole charged particle beam system 300.The vibration caused by mobile platform may cause translation error or displacement error more than one axis.For example, when checking the tube die on the wafer on platform, mobile platform may cause dynamic resonance with other mobile or non-mobile components on XY axis, thereby causes platform vibration on Z axis.

[0205] One of several challenges encountered includes the loss of inspection resolution due to vibration and insufficient vibration compensation, etc. In existing charged particle beam systems, the platform is mechanically coupled to the housing, and the vibrations therefore caused by moving the platform can cause vibrations in the housing and components attached thereto. For example, the vibrations of the platform can cause vibrations in the housing, the positioning sensors attached to the surface of the housing, the charged particle beam columns attached to the housing, etc. Although the positioning sensors can be employed to determine the vibrations of the platform or the wafers disposed thereon, the vibrations of the charged particle beam columns and the positioning sensors themselves may not be detected or may be insufficiently detected, causing inaccurate beam deflection signals applied to the beam controller, and thereby resulting in a loss of inspection resolution, and resulting in reduced inspection throughput.

[0206] Furthermore, in existing inspection systems such as SEMs, positioning sensor measurements from the stage can be asynchronous with the application of actuation signals to the beam deflector to compensate for vibration, resulting in inaccurate compensation of vibration and loss of inspection resolution. One cause of this timing mismatch is the delay caused by digital signal processing of the vibration signal to generate the vibration compensation signal. Furthermore, currently employed vibration detection and correction techniques may not be configured to adequately distinguish between various vibration modes of the stage, such as tilt, torsion, rotation, etc., and thus vibration may be undercompensated, overcompensated, or uncompensated. Therefore, it would be desirable to provide systems and methods to adequately identify vibration modes and compensate for vibration based on the identification, and to dynamically predict vibration to accurately compensate for computational and measurement delays.

[0207] Now refer to Figure 14 , Figure 14 1 is a schematic diagram illustrating the translation axis and rotation axis of platform 1450 (e.g., which may be platform 201) in a charged particle beam system consistent with an embodiment of the present disclosure. In some embodiments, platform 1450 may include a wafer platform, a wafer chuck, a sample holder, or a calibration unit. Samples including but not limited to wafers or devices to be imaged may be disposed on platform 1450. For example, the sample may be secured to platform 1450 via a vacuum-assisted securing mechanism. In some embodiments, a wafer chuck (not shown) may be secured to platform 1450, and the sample may be disposed on the wafer chuck. In this configuration, the wafer chuck may be mechanically coupled to platform 1450, and the sample may be secured to the wafer chuck using mechanical coupling, vacuum-assisted components, or a combination thereof.

[0208] In some embodiments, platform 1450 may include an adjustable platform with six degrees of freedom. Figure 14 As indicated in , the platform 1450 can be configured to move in one or more axes of linear translation, such as the X-, Y-, or Z-axis, or in one or more axes of rotation, such as the Rx-, Ry-, or Rz-axis. In some embodiments, the platform 1450 can be positioned so that the Z-axis is substantially parallel to the principal optical axis (e.g., Figure 8 The primary optical axis 801 is substantially perpendicular to the primary optical axis 802, and the X-axis and Y-axis are substantially perpendicular to the primary optical axis. In some embodiments, the platform 1450 can be tilted along one or more of the rotation axes to adjust factors including, but not limited to, the amount of interaction between the primary charged particle beam and the sample, the area of ​​the sample to be examined, the desired analysis, etc.

[0209] In some embodiments, the moving platform 1450 can cause vibrations about any translational or rotational axis. For example, moving the platform 1450 along the XY plane can cause vibrations of the platform 1450 about a roll axis (Rx axis) or a pitch axis (Ry axis) or a yaw axis (Rz axis) or a combination thereof. In some embodiments, the vibrations of the platform 1450 can have six degrees of freedom for movement, and the vibrations can include one or more vibration modes about one or more axes (such as rotation, rocking, tilting, shifting, etc.). It can be desirable to detect, isolate, and identify the vibration modes of the platform 1450 to compensate for the vibrations via a beam deflection signal configured to adjust characteristics of the incident primary charged particle beam, such as the X / Y position of the beam at the sample or the depth of focus of the beam. Although Figure 14 The translational and rotational axes are illustrated for the exemplary platform 1450 with respect to movement and vibration induced thereby, but it is understood that the housing, SEM column, positioning sensor, etc. can also vibrate about one or more translational and rotational axes.

[0210] Now refer to Figure 15 , Figure 15 The charged particle beam system 1500 is shown in accordance with an embodiment of the present disclosure. The charged particle beam system 1500 may include a housing 1510, positioning sensors 1522 and 1524 disposed on the housing 1510, acceleration sensor(s) 1526, a charged particle beam column 1530 (also referred to herein as an SEM column), and a platform 1560 (which may be a housing). Figure 2-Figure 4 The charged particle beam system 1500 may further include a control module 1570 configured to receive the vibration signal and generate a vibration compensation signal to compensate for vibration of one or more components of the charged particle beam system 1500. The control module 1570 may include: a signal processor 1572 including a processor 1574 configured to process signals received from the positioning sensors 1522 and 1524; an acceleration sensor 1526; a digital image controller 1576 configured to receive a beam scanning signal 1575; and an actuator 1578 configured to generate a beam deflection signal 1580 to be applied to the SEM column 1530. Alternatively, the charged particle beam system 1500 (such as an electron beam system) may be Figure 1 EBI system 100 or Figure 2 It is understood that, although not explicitly described, the charged particle beam system 1500 may include other standard or non-standard components to perform functions including, but not limited to, beam focusing, beam deflection, electron detection, beam current limiting, etc. It is understood that the components described may suitably perform more or fewer functions than those discussed.

[0211] like Figure 15 As shown, the charged particle beam system 1500 may include a housing 1510 configured to house components including, but not limited to, a platform 1560, a wafer chuck 1562, a sample 1550, positioning sensors 1522 and 1524, portions of a charged particle beam column 1530, and the like. In some embodiments, the housing 1510 may be substantially similar to Figure 1 of Room 101 and can be performed with Figure 1 It should be understood that although a portion of the charged particle beam column 1530 is shown as being housed within the housing chamber 1510 , the charged particle beam column 1530 may be housed entirely within the housing chamber 1510 .

[0212] In some embodiments, the housing 1510 can be configured to house the electromechanical components of the charged particle beam column 1530. In the context of the present disclosure, the electromechanical components of the charged particle beam column 1530 can include, but are not limited to, the platform 1560, the wafer chuck 1562, the sample 1550, the platform motion control motor, the drive, etc. The housing 1510 can be placed on an anti-vibration platform or a vibration damping platform (not shown) to minimize the impact of vibration on the overall performance and inspection resolution of images obtained by the charged particle beam system 1500.

[0213] In some embodiments, the platform 1560 can be configured to move in one or more of the X-, Y-, Z-, Rx-, Ry-, or Rz-axes (such as about Figure 14 1450). The platform 1560 may include a wafer chuck 1562 disposed and secured thereto. In some embodiments, the platform 1560 may be configured to move in the X and Y axes, and the wafer chuck 1562 may be configured to move in the Z axis. The sample 1550 may be placed on the wafer chuck 1562 using mechanical clamping or vacuum assistance or other suitable non-contact clamping mechanisms. For example, the wafer chuck 1562 may include a vacuum sample holder configured to hold and secure the sample 1550 while the sample 1550 is being moved in one or more axes for inspection. In some embodiments, the wafer chuck 1562 may be configured to be charged to adjust the landing energy of the incident primary charged particle beam, etc. It should be understood that the sample 1550 may be placed directly on the platform 1560, which is capable of adjusting its positioning in one or more axes, thereby eliminating the use of the wafer chuck 1562.

[0214] In some embodiments, the platform 1560 can be mechanically coupled to the housing chamber 1510 so that vibrations of the platform 1560 can also cause vibrations of the housing chamber 1510. In the context of the present disclosure, mechanical coupling refers to being physically attached to a portion of the housing chamber 1510 (e.g., via multiple intermediate components) or physically contacting a portion of the housing chamber 1510. The platform 1560 can be mechanically coupled to the housing chamber 1510 using techniques including, but not limited to, heat welding, spot welding, riveting, welding, gluing, and the like. In some embodiments, the coupling mechanism can depend on the effect of the mechanism on the vacuum pressure within the housing chamber 1510. For example, some metal glues may degas, causing virtual leaks in the housing chamber 1510, and thus may have a negative impact on the overall inspection resolution of the charged particle beam system 1500.

[0215] The charged particle beam system 1500 can include a charged particle beam column 1530 configured to generate a charged particle beam (e.g., an electron beam) and focus the charged particle beam on a sample 1550. In some embodiments, the SEM column 1530 can be referred to as an electro-optical assembly. The electro-optical assembly can include a charged particle source configured to generate charged particles and a plurality of lenses (optical and electromagnetic) and an aperture configured to focus the generated charged particle beam on the sample 1550. In some embodiments, the SEM column 1530 can be mechanically coupled to a portion of the housing 1510 such that vibrations of the housing 1510 can induce vibrations in the SEM column 1530.

[0216] Charged particle beam system 1500 may include positioning sensors 1522 and 1524, which are configured to determine the displacement of platform 1560. Positioning sensors 1522 and 1524 may include laser interferometers. It should be understood that the positioning sensing system of charged particle beam system 1500 may include more than one positioning sensor and other suitable components (e.g., signal amplifiers, bandpass filters, data storage units, data processing units, etc.).

[0217] In some embodiments, position sensors 1522 and 1524 may include a laser diode sensor assembly including a one-dimensional position sensitive detector (1-D PSD) or a linear array of photodiodes, etc. In some embodiments, position sensors 1522 and 1524 may be configured to determine a lateral displacement of platform 1560. As referred to herein, the lateral displacement of platform 1560 may correspond to a difference between an actual position of platform 1560 on the X-axis or Y-axis and a target position.

[0218] In some embodiments, positioning sensors 1522 and 1524 can be configured to detect vibration modes of platform 1560. For example, positioning sensor 1522 can be configured to detect vibration modes such as torsion, tilt, rotation on the X-axis, and positioning sensor 1524 can be configured to detect vibration modes such as torsion, tilt, rotation on the Y-axis. In some embodiments, more than two positioning sensors can be used. For example, a first positioning sensor is used to detect vibration along the X-axis, a second positioning sensor is used to detect vibration along the Y-axis, a third sensor is used to detect vibration around the Rx-axis, and a fourth sensor is used to detect vibration around the Ry-axis. It should be understood that fewer or more positioning sensors (such as laser interferometers) can be used based on the desired sensing complexity and accuracy, application, sample, etc. Other positioning sensing and vibration detection technologies can be used as appropriate.

[0219] Exemplary positioning sensors 1522 and 1524 can be configured to communicate with control module 1570 (described in detail later) so that the output of positioning sensors 1522 and 1524 is analyzed and used to further adjust beam characteristics to compensate for vibration. Positioning sensors 1522 and 1524 can also be configured to generate output signals comprising displacement signals. In certain embodiments, the output data from one or more positioning sensors 1522 and 1524 can be used to modify beam focusing, beam energy, beam scanning speed, beam scanning frequency, beam scanning duration or beam scanning range by applying a beam deflection signal to the charged particle beam system 1500. It should be understood that other suitable components of the focused beam can be adopted.

[0220] In some embodiments, one or more positioning sensors 1522 and 1524 may be disposed on a surface of the housing 1510. In a configuration including a laser interferometer as the positioning sensor 1522 or 1524, the optical detector surface of the laser interferometer may be positioned to receive an optical signal representing displacement or vibration of the platform 1560 or the sample 1550. In some embodiments, the positioning sensors 1522 and 1524 may be mechanically coupled to the housing 1510 or otherwise suitably mounted on the housing 1510. In some embodiments, the positioning sensors 1522 and 1524 may be configured to adjust the positioning of the platform 1560 or the sample 1550 along one or more of the X, Y, Z, Rx, Ry, and Rz axes, and to detect vibration along one or more of the X, Y, Z, Rx, Ry, and Rz axes.

[0221] In some embodiments, positioning sensors 1522 and 1524 may include, for example, a homodyne laser interferometer or a heterodyne laser interferometer. A homodyne laser interferometer uses a single-frequency laser source, while a heterodyne laser interferometer uses a laser source with two closely spaced frequencies. The laser source may include a He-Ne gas laser that emits laser light at a wavelength of 633 nm. It should be understood that other laser sources emitting at single or multiple wavelengths or frequencies may also be used as appropriate.

[0222] As an example, platform positioning or vibration detection using a laser interferometer can include two separate laser beams, two separate laser beams are directed to a reference mirror and a mirror attached to the platform in each direction. The interferometer can compare the positioning of the platform mirror with the positioning of the reference mirror to detect and correct any platform positioning errors. For example, one laser interferometer is used for the X axis and a second laser interferometer is used for the Y axis. In some embodiments, more than one laser interferometer can be used for a single axis, such as the X axis or the Y axis. Other suitable technologies can also be used. In some embodiments, such as Figure 15 As shown, additional laser interferometers may be employed for vibration detection on the Rx and Ry axes.

[0223] Among the challenges encountered in charged particle beam systems such as SEMs is the loss of inspection resolution due to undetected vibrations and insufficient compensation for detected vibrations. For example, in existing inspection systems, vibrations of the platform 1560 may induce vibrations in the housing 1510, which in turn may induce vibrations in the SEM column 1530. These vibrations of the SEM column 1530 may remain undetected and, therefore, uncompensated. Therefore, it may be desirable to provide a method or system for detecting, determining, and compensating for vibrations of the SEM column 1530.

[0224] The charged particle beam system 1500 can include an accelerometer 1526 configured to determine the vibration of the SEM column 1530. The accelerometer 1526 can be configured to measure the acceleration of the vibration or motion of the SEM column 1530. In some embodiments, the accelerometer 1526 can include a piezoelectric accelerometer, a capacitive accelerometer, an accelerometer based on a microelectromechanical system (MEMS), or a piezoresistive accelerometer. In a piezoelectric accelerometer configured to measure vibration, the force caused by the change in vibration or motion (acceleration) causes the substance to "squeeze" the piezoelectric material, which generates an electric charge proportional to the force applied thereto. Since charge is proportional to force and mass is constant, charge is also proportional to acceleration.

[0225] In some embodiments, acceleration sensor 1526 may comprise a high-impedance charge-output accelerometer. In this type of accelerometer, a piezoelectric crystal generates an electrical charge that is directly connected to a measuring instrument. In some embodiments, acceleration sensor 1526 may comprise a low-impedance output accelerometer. A low-impedance accelerometer comprises a charge accelerometer and a microcircuit comprising a transistor that converts the charge into a low-impedance voltage signal. A low-impedance accelerometer may generate a voltage signal based on the accelerometer's frequency response or sensitivity. It should be understood that other suitable types of accelerometers may also be employed as appropriate.

[0226] In some embodiments, the accelerometer 1526 can be configured to detect vibrations of the SEM column 1530 and to detect vibration patterns, including but not limited to tilt, rotation, torsion, displacement, etc. In some embodiments, the charged particle beam system 1500 can include more than one accelerometer 1526 mounted on the SEM column 1530. The output signal generated by the accelerometer 1526 can include an electrical signal such as a voltage signal. The accelerometer can generate a voltage signal in response to the detected vibration and based on the detected vibration frequency.

[0227] The charged particle beam system 1500 may include a control module 1570 configured to process a vibration signal of the charged particle beam system 1500 and apply a vibration compensation signal to the SEM column 1530 to compensate for the vibration. In some embodiments, the control module 1570 may include a signal processor 1572, an image controller 1576 configured to receive a beam scanning signal 1575, and an actuator 1578 configured to generate a beam deflection signal 1580 to be applied to the SEM column 1530.

[0228] In existing techniques for vibration detection and compensation, a vibration signal generated by a positioning sensor can be directly added to a beam scanning signal to form a vibration compensation signal. Among several issues with this approach, insufficient vibration compensation can result in a loss of inspection resolution because the vibration compensation signal may not account for vibration modes in all translational and rotational axes. Furthermore, because the vibration signal is directly added to the beam scanning signal, delays between measuring vibration and applying vibration compensation may not be accounted for, causing the controller to generate an under-compensated or over-compensated vibration compensation signal. Therefore, it would be desirable to provide a method for determining vibration compensation based on identified vibration modes and estimating vibration to compensate for computational delays and control sampling delays.

[0229] In some embodiments, the control module 1570 can be configured to receive signals associated with vibration detection from the position sensors 1522 and 1524 and the accelerometer 1526. The control module 1570 can include a signal processor 1572 configured to receive signals from the position sensors 1522 and 1524 and the accelerometer 1526, and the control module 1570 can also be configured to utilize the received signals to identify vibration patterns of the platform 1560 and the SEM column 1530. In some embodiments, the signal processor 1572 can include a field programmable gate array (FPGA)-based controller and can be configured to process vibration signals from the position sensors 1522 and 1524 and the accelerometer 1526. In some embodiments, the signal processor 1572 can also be referred to as a digital vibration estimation controller (DVEC) and can be configured to identify vibration patterns based on input vibration signals from the position sensors 1522 and 1524 and the accelerometer 1526.

[0230] In some embodiments, the signal processor 1572 may be configured to use a dynamic vibration estimation algorithm (described later in detail) executed by, for example, the processor 1574. Figure 16 ), determine the vibration compensation signal based on the signals from the positioning sensors 1522 and 1524 and the acceleration sensor 1526. The signal processor 1572 may include other related components (not shown), including but not limited to data storage units, memories, timing control circuits, etc. to support the processor 1574 or signal processor 1572.

[0231] In some embodiments, signal processor 1572 can be configured to determine a predicted vibration signal based on signals from positioning sensors 1522 and 1524 and acceleration sensor 1526 using a dynamic vibration estimation algorithm executed by, for example, processor 1574. The predicted vibration signal can be applied to digital image controller 1576 in combination with beam scanning signal 1575. Beam scanning signal 1575 can be applied directly to digital image controller 1576 or can be applied to digital image controller 1576 via control module 1570. In some embodiments, beam scanning signal 1575 can be generated by a user, a host computer, or a beam control module (e.g., Figure 3The beam control module 365 of the embodiment of the present invention is generated by the digital image controller 1576. The digital image controller 1576 can be configured to generate a compensated beam scanning signal based on the beam scanning signal 1575 and the predicted vibration signal from the signal processor 1572. In some embodiments, although not preferred, the signal processor 1572 can also be configured to receive the beam scanning signal 1575 from the host and determine the predicted vibration signal based on signals from the positioning sensors 1522 and 1524 and the acceleration sensor 1526.

[0232] In some embodiments, the control module 1570 may further include an actuator 1578 configured to receive the compensated beam scanning signal from the digital image controller 1576 and generate a beam deflection signal 1580 based on the received compensated beam scanning signal. In some embodiments, the actuator 1578 may include a digital wave generator configured to generate an electrical waveform using digital signal processing techniques. The beam deflection signal 1580 may be applied to the SEM column 1530. In some embodiments, the beam deflection signal 1580 may be applied to the SEM column 1530 by a beam deflection controller (e.g., Figure 3 beam deflection controller 367) or a beam control module (e.g., Figure 3 1570 ). The beam deflection signal 1580 may be applied to the SEM column 1530 by, for example, adjusting the characteristics of the primary charged particle beam based on the detected vibration to compensate for vibrations of the charged particle beam system 1500. It should be understood that although the signal processor 1572, the digital image controller 1576, and the actuator 1578 are illustrated as components of the control module 1570, one or more of these components may be used as independent elements of the charged particle beam system 1500. For example, the control module 1570 may include the signal processor 1572 and the digital image controller 1576, while the actuator 1578 may be operated independently. It should also be understood that the charged particle beam system 1500 may not include the control module 1570, but rather include the signal processor 1572, the digital image controller 1576, and the actuator 1578 as discrete components.

[0233] Now refer to Figure 16 , Figure 16The steps of an exemplary algorithm 1600 for determining a vibration estimate and compensation signal consistent with embodiments of the present disclosure are illustrated. One or more steps of algorithm 1600 may be performed, for example, by processor 1574. In some embodiments, algorithm 1600 may be performed in real time. In the context of the present disclosure, "real time" may refer to the occurrence of events within a very short time period on the order of milliseconds or microseconds. In other words, events occur with negligible delay between them. For example, in the context of the present disclosure, step 1610 may be performed immediately after vibration is measured by positioning sensors 1522 and 1524 and acceleration sensor 1526.

[0234] In step 1610 of algorithm 1600, vibration measurement signals from positioning sensors 1522 and 1524 and accelerometer 1526 can be utilized to identify vibration modes of platform 1560 and SEM column 1530, respectively. Signal processor 1572 (DVEC) can be configured to perform vibration mode identification. In some embodiments, vibration mode identification can include compatibility of signals from positioning sensors 1522 and 1524 and accelerometer 1526. For example, the vibration measurement signal from accelerometer 1526 can include a voltage signal, while the vibration measurement signals from positioning sensors 1522 and 1524 can include a distance signal or a displacement signal. In some embodiments, signal processor 1572 can be configured to convert the voltage signal from accelerometer 1526 into a corresponding displacement signal so that the input signals used to identify the vibration modes of platform 1560 and SEM column 1530 are compatible.

[0235] In some embodiments, the vibration mode identification may further include forming a vibration mode identification matrix of vibration measurements from the six degrees of freedom of the platform 1560 and the SEM column 1530 based on the compatible vibration measurement signals. The vibration mode identification matrix may include measurements of vibration in each direction (X, Y, Z, Rx, Ry, and Rz). In this step, the vibration mode of the SEM column 1530 may be identified with reference to the platform 1560.

[0236] The vibration pattern identification in step 1610 may also include decoupling the vibrations from positioning sensors 1522 and 1524 from the vibrations from platform 1560 using the vibration measurements from accelerometer 1526. Because positioning sensors 1522 and 1524 may be mounted to or mechanically coupled to housing 1510, vibrations of housing 1510 may cause vibrations in positioning sensors 1522 and 1524. The vibration measurements obtained by positioning sensors 1522 and 1524 may include vibration patterns and vibrations of positioning sensors 1522 and 1524 in addition to the vibrations of platform 1560. Therefore, it may be desirable to decouple and isolate the vibrations of platform 1560 from the vibrations of positioning sensors 1522 and 1524.

[0237] Based on the vibration mode identification matrix, the vibration modes of the SEM column 1530 and platform 1560 may be determined, and corresponding output signals may be generated.

[0238] In step 1620, the identified vibration modes from step 1610 may be used to estimate the vibrations of the SEM column 1530 and platform 1560 using a simulation model or a mathematical model. In some embodiments, a three-dimensional finite element analysis model (3D-FEM) may be used to estimate the vibrations of the SEM column 1530 and platform 1560 along any or all of the X, Y, Z, Rx, Ry, and Rx axes.

[0239] In step 1630, the vibration of the SEM column 1530 and platform 1560 can be predicted based on the estimated vibration from step 1620. One of the several problems encountered in digital signal processing techniques includes computation and measurement delays, also known as "single-sample delays." To mitigate the negative effects of signal processing delays, it may be desirable to determine and apply a "predicted" vibration signal to compensate for the vibration.

[0240] In this context, a single-sample delay can refer to the delay between the measurement of vibration and the application of the actuation signal or beam deflection signal 1580. For example, a vibration measurement can be performed at a first timestamp, and a correction signal or beam deflection signal for compensating for the measured vibration can be performed at a second timestamp, where the time difference between the first timestamp and the second timestamp is the amount of time required to process the measured vibration signal and generate the vibration compensation signal. Due to the time delay, the measured vibration and the applied compensation signal are asynchronous, resulting in inaccurate vibration compensation.

[0241] To compensate for digital signal processing delays, vibrations may be predicted or anticipated based on the estimated vibrations of the SEM column 1530 and platform 1560 at the second timestamp so that the vibration measurement and application of the compensation signal may be synchronized.

[0242] In some embodiments, the steps of the algorithm 1600 can be performed to predict vibrations in one or more of the X, Y, or Rz axes of the SEM column 1530 and the platform 1560. One of several ways to compensate for vibrations in the Z, Rx, or Ry axes can include adjusting the depth of focus of the incident primary charged particle beam by adjusting the landing energy, etc.

[0243] Now refer to Figure 17 , Figure 17 A flow chart illustrating an exemplary method 1700 for focusing a charged particle beam (eg, an electron beam) on a sample in a charged particle beam system consistent with an embodiment of the present disclosure is shown. The method for focusing the electron beam on the sample may be performed by Figure 1 Charged particle EBI system 100, Figure 2 It should be understood that the charged particle beam system 1500 can be controlled to image a sample (e.g., Figure 15 Observing, imaging, and inspecting a sample (1550) or a region of interest on the sample. Imaging can include scanning the sample to image at least a portion of the sample, a pattern on the sample, or the sample itself. Inspecting the sample can include scanning the sample to inspect at least a portion of the sample, a pattern on the sample, or the sample itself. Observing the sample can include monitoring the sample or the region of interest on the sample for reproducibility and repeatability of the pattern.

[0244] Primary charged particle beam (e.g. Figure 2 The primary charged particle beam 220 is generated from a charged particle source. Figure 2-Figure 4 Platform 201, Figure 15 The sample on the platform 1560 is irradiated with a primary charged particle beam. In some embodiments, at least a portion of the sample can be irradiated with at least a portion of the primary charged particle beam. The primary charged particle beam can be, for example, an electron beam generated from an electron source. The electron source can include, but is not limited to, thermionic emission of electrons from a tungsten filament or Lab6 cathode, or field emission of electrons from a tungsten / ZrO2 cold cathode.

[0245] The sample can be placed directly on the platform. In some embodiments, the sample can be placed on a surface such as a sample holder (e.g., Figure 15 The geometric centers of the sample, sample holder, and platform can be aligned with each other and with the principal optical axis (e.g., Figure 8The sample, sample holder, and platform can be aligned with the principal optical axis 801 of the microscope. The sample, sample holder, and platform can be arranged in a plane perpendicular to or substantially perpendicular to the principal optical axis. In some embodiments, the sample or platform can be tilted off-axis so that the primary charged particle beam is incident on the sample at an angle less than or greater than 90°. In some embodiments, the sample and platform can be mechanically coupled so that displacement of the platform in any of the X, Y, or Z axes results in corresponding displacement of the sample.

[0246] The platform can be connected to the housing (e.g. Figure 15 The housing 1510) is mechanically coupled to the platform so that vibrations of the platform can also cause vibrations of the housing. The platform can be mechanically coupled to the housing using techniques including but not limited to heat welding, spot welding, riveting, welding, gluing, etc. The housing can be configured to accommodate the electromechanical components of the charged particle beam column. In the context of the present disclosure, the electromechanical components of the charged particle beam column can refer to parts or elements, which include but are not limited to platforms, wafer chucks, samples, platform motion control motors, drives, etc. The housing can be placed on an anti-vibration platform or a vibration damping platform to minimize the impact of vibrations on the overall performance and inspection resolution of the images obtained. In some embodiments, the SEM column (for example, Figure 15 The charged particle beam column 1530) can be referred to as an electro-optical assembly. The electro-optical assembly can include a charged particle source configured to generate charged particles and a plurality of lenses (optical and electromagnetic) and apertures configured to focus the generated charged particle beam on the sample. The SEM column can be mechanically coupled to a portion of the housing so that vibrations of the housing can induce vibrations of the SEM column.

[0247] In step 1710, an acceleration sensor (eg, Figure 15An accelerometer 1526) can be used to detect vibrations of an electro-optical component of a charged particle beam system. The electro-optical component may include an SEM column. The accelerometer can be configured to measure the acceleration of the vibration or motion of the SEM column. The accelerometer can include a piezoelectric accelerometer, a capacitive accelerometer, a microelectromechanical system (MEMS)-based accelerometer, or a piezoresistive accelerometer. In a piezoelectric accelerometer configured to measure vibrations, the force caused by the change in vibration or motion (acceleration) generates an electric charge proportional to the force applied thereto. Since charge is proportional to force and mass is constant, charge is also proportional to acceleration. The accelerometer can include a high-impedance charge output accelerometer or a low-impedance output accelerometer configured to generate a voltage signal in response to detected vibrations and based on the detected vibration frequency. The accelerometer can detect vibrations of the SEM column and detect vibration modes, including but not limited to tilt, rotation, torsion, displacement, etc. The charged particle beam system can include more than one accelerometer mounted on the SEM column. The output signal generated by the acceleration sensor may include an electrical signal such as a voltage signal.

[0248] In step 1720, the positioning sensor (e.g., Figure 15 The positioning sensor 1522) can be used to detect vibrations of the electromechanical components of the charged particle beam system. The electromechanical components of the charged particle beam system may include a platform, a wafer chuck, a sample, a platform motion control motor, a drive, etc. One or more positioning sensors can be used to detect vibrations and vibration patterns of the platform in the X or Y axis. The positioning sensor(s) may include a laser diode sensor assembly, the laser diode sensor assembly including a one-dimensional positioning sensitive detector (1-D PSD) or a linear array of photodiodes, etc. The positioning sensor can be configured to determine the lateral displacement of the platform and detect vibration patterns (such as torsion, tilt, rotation, shift) of the platform in the translation X or Y axis and the rotation Rx and Ry axes. In some embodiments, a first positioning sensor is used to detect vibrations along the X axis, a second positioning sensor is used to detect vibrations along the Y axis, a third sensor is used to detect vibrations around the Rx axis, and a fourth sensor is used to detect vibrations around the Ry axis. The positioning sensor(s) can be connected to a control module (e.g., Figure 15 The control module 1570) communicates with the positioning sensor so that the output signal of the positioning sensor(s) can be analyzed and used to further adjust the beam characteristics to compensate for vibration. The output signal may include a displacement signal.

[0249] The positioning sensor(s) may be disposed on a surface of the housing or mounted on the housing. The positioning sensor(s) may include a laser interferometer. The positioning sensor(s) may be mechanically coupled to the housing so that vibrations of the housing cause the positioning sensor(s) to vibrate. The positioning sensor(s) may be configured to adjust the positioning of the platform or sample on one or more of the X-axis, Y-axis, Z-axis, Rx-axis, Ry-axis, and Rz-axis, and to detect vibrations on one or more of the X-axis, Y-axis, Z-axis, Rx-axis, Ry-axis, and Rz-axis. The positioning sensor(s) may include, for example, a homodyne laser interferometer or a heterodyne laser interferometer. A homodyne laser interferometer uses a single-frequency laser source, while a heterodyne laser interferometer uses a laser source having two close frequencies. The laser source may include a He-Ne gas laser that emits laser light having a wavelength of 633 nm. It should be understood that other laser sources emitting at single or multiple wavelengths or frequencies may also be used as appropriate. The positioning sensor(s) may generate a displacement signal or a distance signal based on the frequency of the vibration or the type of vibration mode detected.

[0250] In step 1730, a vibration compensation signal may be applied to the SEM column to compensate for vibrations of the electro-optical and electromechanical components. The vibration compensation signal may be generated by a controller (e.g., Figure 15 The controller is also referred to herein as a dynamic vibration estimation controller (DVEC) and is generated by a signal processor 1572. The controller can be configured to: receive signals associated with vibration detection from the positioning sensor(s) and the acceleration sensor; process the received signals; and generate a vibration compensation signal based on the processed vibration signals. The DVEC may include a field programmable gate array (FPGA)-based controller and may be configured to process vibration signals from the positioning sensor(s) and the acceleration sensor(s).

[0251] The DVEC can be configured to predict or calculate vibration compensation signals based on signals from the positioning sensor(s) and the acceleration sensor(s) using a dynamic vibration estimation algorithm. The algorithm can include the following steps: identifying vibration modes of the SEM column and platform in each of the X-axis, Y-axis, Z-axis, Rx-axis, Ry-axis, and Rz-axis based on vibration measurements from the positioning sensor(s) and the acceleration sensor(s); estimating vibrations of the SEM column and platform based on the identified vibration modes; and predicting or calculating vibrations in the six degrees of freedom to be applied to the SEM column.

[0252] The algorithm can be implemented in real time and executed by the DVEC. In the vibration mode identification step, the vibration measurement signals from the positioning sensor(s) and the acceleration sensor(s) can be utilized to identify the vibration modes of the platform and the SEM column, respectively. The DVEC can perform the vibration mode identification. The identification of the vibration mode can include compatibility of the signals from the positioning sensor(s) and the acceleration sensor(s). For example, the vibration measurement signal from the acceleration sensor can include a voltage signal, while the vibration measurement signal from the positioning sensor can include a distance signal or a displacement signal. The DVEC can convert the voltage signal from the acceleration sensor into a corresponding displacement signal so that the input signals from the platform and the SEM column for identifying the vibration mode are compatible.

[0253] Identification of the vibration mode may also include forming a vibration mode identification matrix of vibration measurements from the six degrees of freedom for the platform and the SEM column based on the compatible vibration measurement signals. The vibration mode identification matrix may include measurements of vibration in each direction (X, Y, Z, Rx, Ry, and Rz). In this step, the vibration mode of the SEM column may be identified with reference to the platform.

[0254] The vibration mode identification can also include decoupling the vibration of the positioning sensor(s) from the vibration of the platform using vibration measurements from the acceleration sensor(s). Because the positioning sensor(s) can be mounted to the housing or mechanically coupled to the housing, vibrations of the housing can cause vibrations of the positioning sensor(s). In addition to the vibrations of the platform, the vibration measurements obtained by the positioning sensor(s) can include vibrations and vibration modes of the positioning sensor(s). Thus, the vibrations of the platform are decoupled and isolated from the vibrations of the positioning sensor(s). Based on the vibration mode identification matrix, the vibration modes of the SEM column and platform can be determined, and corresponding output signals can be generated.

[0255] The identified vibration modes can be used to estimate the vibration of the SEM column and platform using a simulation model or a mathematical model. A three-dimensional finite element analysis model (3D-FEM) can be used to estimate the vibration of the SEM column and platform along the X, Y, Z, Rx, Ry, and Rz axes. It should be understood that other simulation models can be used as appropriate.

[0256] The vibration of the SEM column and platform can be predicted based on the estimated vibration. One of the problems encountered in digital signal processing techniques is the computation and measurement delay, also known as "single-sample delay." To mitigate the negative effects of signal processing delays, it may be desirable to determine and apply a "predicted" vibration signal to compensate for the vibration.

[0257] In this context, single-sample delay can refer to the delay between the measurement of vibration and the application of an actuation signal or beam deflection signal. For example, a vibration measurement can be performed at a first timestamp, and a correction signal or beam deflection signal used to compensate for the measured vibration can be applied at a second timestamp, where the time difference between the first timestamp and the second timestamp is the amount of time required to process the measured vibration signal and generate the vibration compensation signal. Due to the time delay, the measured vibration and the applied compensation signal are asynchronous, resulting in inaccurate vibration compensation. To compensate for the digital signal processing delay, the vibration can be predicted or anticipated based on the estimated vibration of the SEM column and platform at the second timestamp, so that the vibration measurement and the application of the compensation signal can be synchronized.

[0258] The predicted vibration signal can be compared with the beam scanning signal (e.g. Figure 15 The beam scanning signal 1575) is applied to the image controller (e.g., Figure 15 The beam scanning signal may be applied directly to the digital image controller or may be applied to the digital image controller via a control module. In some embodiments, the beam scanning signal may be applied by a user, a host, or a beam control module (e.g., Figure 3 The image controller may be configured to generate a compensated beam scanning signal based on the beam scanning signal and a predicted vibration signal from a signal processor or controller.

[0259] Actuator (e.g. Figure 15 The actuator 1578 may be configured to receive the compensated beam scanning signal from the image controller and generate a beam deflection signal (eg, Figure 15 The actuator may include a digital wave generator configured to generate an electrical waveform using digital signal processing techniques. The beam deflection signal may be applied to the SEM column to adjust beam characteristics and compensate for vibrations. The beam deflection signal may be applied to the SEM column by a beam deflection controller (e.g., Figure 3 The beam deflection controller 367) or beam control module is applied to the SEM column. The beam deflection signal can be configured to adjust the characteristics of the primary charged particle beam to compensate for vibrations of the charged particle beam system, for example, based on the detected vibrations. It should be understood that although the signal processor, digital image controller, and actuator are illustrated as components of the control module, one or more of these components can be used as independent elements of the charged particle beam system.

[0260] The embodiments may be further described using the following terms:

[0261] 1. A charged particle beam system comprising:

[0262] a stage configured to hold a sample and movable in at least one of an XY and Z axis;

[0263] a position sensing system configured to determine lateral and vertical displacements of the platform; and

[0264] The controller is configured as:

[0265] applying a first signal to deflect the primary charged particle beam incident on the sample to at least partially compensate for the lateral displacement of the stage; and

[0266] A second signal is applied to adjust the focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the stage.

[0267] 2. The system of clause 1, wherein the first signal comprises an electrical signal that affects how the primary charged particle beam is deflected in at least one of the XY axes.

[0268] 3. The system of clause 2, wherein the electrical signal comprises a signal having a bandwidth in the range of 10 kHz to 50 kHz.

[0269] 4. A system according to any of clauses 1 to 3, wherein the lateral displacement corresponds to a difference between a target position of the platform and a current position of the platform in at least one of the XY axes.

[0270] 5. The system of any of clauses 1-4, wherein the controller is further configured to dynamically adjust at least one of the first signal or the second signal during scanning of the primary charged particle beam over the sample.

[0271] 6. The system of any of clauses 1-5, wherein the second signal comprises a voltage signal applied to the stage, the voltage signal affecting how a deflected charged particle beam incident on the sample is focused on the Z-axis.

[0272] 7. The system of clause 6, wherein the voltage signal comprises a signal having a bandwidth in the range of 50 kHz to 200 kHz.

[0273] 8. A system according to any of clauses 1-7, wherein the vertical displacement corresponds to a difference between a target position of the platform on the Z axis and a current position of the platform, and wherein the vertical displacement varies during scanning of the primary charged particle beam over the sample to at least partially compensate for angular rotation about at least one of the X or Y axes.

[0274] 9. The system of any of clauses 1-8, further comprising a platform motion controller, wherein the platform motion controller comprises a plurality of motors configured to be independently controlled by the third signal.

[0275] 10. The system of clause 9, wherein each motor of the plurality of motors is independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam.

[0276] 11. The system of any one of clauses 9 and 10, wherein the third signal comprises a plurality of control signals, each control signal corresponding to at least one motor of the plurality of motors.

[0277] 12. The system of any of clauses 9-11, wherein the plurality of motors comprises at least one of a piezoelectric motor, a piezoelectric actuator, or an ultrasonic piezoelectric motor.

[0278] 13. The system of clause 11, further comprising:

[0279] a first component configured to form an embedded control signal based on a plurality of control signals; and

[0280] The second component is configured to extract at least one control signal of the plurality of control signals from the embedded control signal.

[0281] 14. The system of any of clauses 10-13, wherein leveling of the adjustment platform is based on a geometric model of the actuation output of the platform.

[0282] 15. The system of any of clauses 1-14, wherein the position sensing system uses a combination of laser interferometers and height sensors to determine the lateral and vertical displacements of the platform.

[0283] 16. The system of clause 15, wherein the laser interferometer is configured to determine at least a lateral displacement of the platform.

[0284] 17. The system of clause 15, wherein the height sensor is configured to determine at least a vertical displacement of the platform.

[0285] 18. A charged particle beam system comprising:

[0286] a platform configured to hold a sample and capable of moving in at least a Z-axis;

[0287] a positioning sensing system configured to determine the vertical displacement of the platform, and

[0288] A controller is configured to apply a voltage signal to the stage that affects how a charged particle beam incident on the sample is focused on the Z-axis.

[0289] 19. A system according to claim 18, wherein the vertical displacement can correspond to a difference between a target position of the platform on the Z axis and a current position of the platform, and wherein the vertical displacement varies during scanning of the primary charged particle beam over the sample to at least partially compensate for angular rotation about at least one of the X or Y axes.

[0290] 20. The system according to any of clauses 18 and 19, wherein the controller is further configured to dynamically adjust the voltage signal during scanning of the primary charged particle beam over the sample.

[0291] 21. The system of any of clauses 18-20, wherein the voltage signal comprises a signal having a bandwidth in the range of 50 kHz to 200 kHz.

[0292] 22. The system of any of clauses 18-21, further comprising a platform motion controller, wherein the platform motion controller comprises a plurality of motors configured to be independently controlled by the control signals.

[0293] 23. The system of clause 22, wherein each motor of the plurality of motors is independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam.

[0294] 24. The system of any of clauses 22 and 23, wherein the control signal comprises a plurality of control signals, each control signal of the plurality of control signals corresponding to at least one motor of the plurality of motors.

[0295] 25. The system of clause 24, further comprising:

[0296] a first component configured to form an embedded control signal based on a plurality of control signals; and

[0297] The second component is configured to extract at least one control signal of the plurality of control signals from the embedded control signal.

[0298] 26. The system according to any of clauses 18-25, wherein the positioning system comprises a height sensor to determine the vertical displacement of the platform.

[0299] 27. A method for irradiating a sample disposed on a platform in a charged particle beam system, the method comprising:

[0300] generating a primary charged particle beam from a charged particle source;

[0301] determining a lateral displacement and a vertical displacement of a platform, wherein the platform is movable in at least one of an X, Y, and Z axis;

[0302] applying a first signal to deflect the primary charged particle beam incident on the sample to at least partially compensate for the lateral displacement of the stage; and

[0303] A second signal is applied to the stage to adjust a focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the stage.

[0304] 28. The method of clause 27, wherein the first signal comprises an electrical signal that affects how the primary charged particle beam is deflected in at least one of the XY axes.

[0305] 29. The method of clause 28, wherein the electrical signal comprises a signal having a bandwidth in the range of 10 kHz to 50 kHz.

[0306] 30. A method according to any of clauses 27 to 29, wherein the lateral displacement corresponds to a difference between a target position of the platform and a current position of the platform in at least one of the XY axes.

[0307] 31. A method according to any of clauses 27 to 30, wherein the vertical displacement corresponds to a difference between a target position of the platform on the Z axis and a current position of the platform, and wherein the vertical displacement varies during scanning of the primary charged particle beam over the sample to at least partially compensate for an angular rotation about at least one of the X or Y axes.

[0308] 32. The method of any of clauses 27-31, further comprising dynamically adjusting at least one of the first signal or the second signal during scanning of the primary charged-particle beam over the sample.

[0309] 33. The method of any of clauses 27-32, wherein the second signal comprises a voltage signal applied to the stage, the voltage signal affecting how a deflected charged particle beam incident on the sample is focused on the Z-axis.

[0310] 34. The method of clause 33, wherein the voltage signal comprises a signal having a bandwidth in the range of 50 kHz to 200 kHz.

[0311] 35. The method of any of clauses 27-34, further comprising applying a third signal to a platform motion controller, wherein the platform motion controller comprises a plurality of motors configured to be independently controlled by the third signal.

[0312] 36. The method of clause 35, wherein each motor of the plurality of motors is independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam.

[0313] 37. The method of any of clauses 35 and 36, wherein the third signal comprises a plurality of control signals, each control signal of the plurality of control signals corresponding to at least one motor of the plurality of motors.

[0314] 38. The method of any of clauses 35-37, wherein applying the third signal comprises:

[0315] embedding the plurality of control signals to form an embedded control signal; and

[0316] At least one control signal of the plurality of control signals is extracted from the embedded control signal.

[0317] 39. A method according to any of clauses 36-38, wherein adjusting the levelling of the platform is based on a geometric model of the actuation output of the platform.

[0318] 40. A method according to any of clauses 27-39, wherein the lateral and vertical displacements of the platform are determined by a positioning sensing system.

[0319] 41. The method of clause 40, wherein the position sensing system uses a combination of a laser interferometer and a height sensor to determine the lateral and vertical displacements of the platform.

[0320] 42. The method of clause 41, wherein the laser interferometer is configured to determine the lateral displacement of the platform.

[0321] 43. The method of clause 41, wherein the height sensor is configured to determine a vertical displacement of the platform.

[0322] 44. A method for irradiating a sample disposed on a platform in a charged particle beam system, the method comprising:

[0323] generating a primary charged particle beam from a charged particle source;

[0324] determining a vertical displacement of a platform, wherein the platform is movable in a Z-axis; and

[0325] A voltage signal is applied to the stage to adjust a focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the stage.

[0326] 45. A method according to claim 44, wherein the vertical displacement corresponds to a difference between a target position of the platform on the Z axis and a current position of the platform, and wherein the vertical displacement varies during scanning of the primary charged particle beam over the sample to at least partially compensate for angular rotation about at least one of the X or Y axes.

[0327] 46. ​​The method according to any of clauses 44 and 45, further comprising:

[0328] determining a lateral displacement of a platform, wherein the platform is movable in at least one of an XY axis; and

[0329] A beam deflection signal is applied to deflect the focused charged particle beam incident on the sample to at least partially compensate for the lateral displacement.

[0330] 47. The method of any of clauses 44-46, further comprising dynamically adjusting at least one of the voltage signal or the beam deflection signal during scanning of the primary charged particle beam over the sample.

[0331] 48. A method according to any of clauses 44-47, wherein the voltage signal comprises a signal having a bandwidth in the range of 50 kHz to 200 kHz.

[0332] 49. The method of clause 46, wherein the beam deflection signal comprises an electrical signal that affects how the focused charged particle beam is deflected in at least one of the XY axes.

[0333] 50. The method of clause 49, wherein the electrical signal comprises a signal having a bandwidth in the range of 10 kHz to 50 kHz.

[0334] 51. A method according to any of clauses 46 to 50, wherein the lateral displacement corresponds to a difference between a target position of the platform and a current position of the platform in at least one of the XY axes.

[0335] 52. The method of any of clauses 44-51, further comprising applying a control signal to a platform motion controller, wherein the platform motion controller comprises a plurality of motors configured to be independently controlled by the control signal.

[0336] 53. The method of clause 52, wherein each motor of the plurality of motors is independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam.

[0337] 54. The method of any of clauses 52 and 53, wherein the control signal comprises a plurality of control signals, each control signal of the plurality of control signals corresponding to at least one motor of the plurality of motors.

[0338] 55. The method of any of clauses 52-54, wherein the plurality of motors comprises at least one of a piezoelectric motor, a piezoelectric actuator, or an ultrasonic piezoelectric motor.

[0339] 56. The method of any of clauses 52-55, wherein applying the control signal comprises:

[0340] embedding the plurality of control signals to form an embedded control signal; and

[0341] At least one control signal of the plurality of control signals is extracted from the embedded control signal.

[0342] 57. A method according to any of clauses 53-56, wherein adjusting the levelling of the platform is based on a geometric model of the actuation output of the platform.

[0343] 58. A method according to any of clauses 46-57, wherein the lateral and vertical displacements of the platform are determined by a position sensing system.

[0344] 59. The method of clause 58, wherein the position sensing system uses a combination of a laser interferometer and a height sensor to determine the lateral and vertical displacements of the platform.

[0345] 60. The method of clause 59, wherein the laser interferometer is configured to determine the lateral displacement of the platform.

[0346] 61. The method of clause 59, wherein the height sensor is configured to determine a vertical displacement of the platform.

[0347] 62. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of an apparatus to cause the apparatus to perform a method, wherein the apparatus comprises a charged particle source to generate a primary charged particle beam, and the method comprises:

[0348] determining a lateral displacement of a platform, wherein the platform is movable in at least one of an XY axis; and

[0349] The controller is instructed to apply a first signal to deflect the primary charged particle beam incident on the sample to at least partially compensate for the lateral displacement.

[0350] 63. The medium of clause 62, wherein the set of instructions executable by one or more processors of the device causes the device to further perform:

[0351] determining a vertical displacement of a platform, wherein the platform is movable in a Z-axis; and

[0352] The controller is instructed to apply a second signal to adjust the focus of the primary charged particle beam incident on the sample to at least partially compensate for the vertical displacement.

[0353] 64. A medium according to any of clauses 62 and 63, wherein the set of instructions executable by one or more processors of the apparatus causes the apparatus to further perform:

[0354] A third signal is applied to a platform motion controller configured to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam.

[0355] 65. A method of focusing a charged particle beam on a sample, the method comprising:

[0356] irradiating a sample disposed on a platform of a charged particle beam system using a charged particle beam;

[0357] adjusting a position of a first focus of the charged particle beam using the first component of the charged particle system and the reference sample; and

[0358] An electromagnetic field associated with the sample is manipulated using a second component to form a second focus by adjusting the first focus of the charged particle beam with reference to the sample, wherein the second component is located downstream of a focusing component of an objective of the charged particle system.

[0359] 66. The method of clause 65, wherein adjusting the position of the first focus comprises adjusting the positioning of the platform on the Z-axis.

[0360] 67. The method of clause 66, wherein adjusting the position of the platform on the Z axis comprises:

[0361] Using a height sensor to determine the positioning of the sample in the Z-axis; and

[0362] Using the stage motion controller, the positioning of the stage in the Z axis is adjusted based on the determined positioning of the sample.

[0363] 68. A method according to any of clauses 65-67, wherein the first component is configured to adjust the depth of focus of the charged particle beam with reference to the sample.

[0364] 69. A method according to any of clauses 65-68, wherein the first component is located upstream of a focusing component of an objective of the charged particle system.

[0365] 70. The method of clause 69, wherein the first component comprises a charged particle source, an anode of a charged particle source, or a buncher lens, and wherein the first component of the charged particle system is different from the second component of the charged particle system.

[0366] 71. The method of any of clauses 65-70, wherein manipulating the electromagnetic field comprises adjusting an electrical signal applied to the second component of the charged particle system.

[0367] 72. A method according to any of clauses 65-71, wherein the second component of the charged particle system comprises one or more of the objective, the sample, or a control electrode of the stage.

[0368] 73. The method of any of clauses 71-72, wherein adjusting the electrical signal applied to the second component adjusts the landing energy of the charged particle beam on the sample.

[0369] 74. The method of any of clauses 72-73, wherein adjusting the electrical signal comprises:

[0370] adjusting a first component of an electrical signal applied to a control electrode of the objective lens; and

[0371] A second component of the electrical signal applied to the platform is adjusted.

[0372] 75. A method according to item 74, wherein a first component of the electrical signal applied to the control electrode is adjusted, with reference to the sample, to coarsely adjust the first focus of the charged particle beam, and wherein a second component of the electrical signal applied to the platform is adjusted, with reference to the sample, to finely adjust the first focus of the charged particle beam.

[0373] 76. The method according to any of clauses 74-75, wherein the first component of the electric signal is determined based on an acceleration voltage and a landing energy of the charged particle beam.

[0374] 77. A method according to any of clauses 74-76, wherein the first component of the electrical signal comprises a voltage signal having an absolute value in the range of 5 kV to 10 kV, and wherein the second component of the electrical signal comprises a voltage signal having an absolute value in the range of 0 V to 150 V.

[0375] 78. The method of any of clauses 65-77, wherein manipulating the electromagnetic field further comprises adjusting an electric field configured to affect a characteristic of the charged particle beam.

[0376] 79. The method of any of clauses 65-78, wherein manipulating the electromagnetic field further comprises adjusting a magnetic field configured to affect a characteristic of the charged particle beam.

[0377] 80. The method of any of clauses 78 and 79, wherein the characteristic of the charged particle beam comprises at least one of a path, a direction, a velocity or an acceleration of the charged particle beam.

[0378] 81. The method of any of clauses 73-80, wherein the landing energy of the charged particle beam is in the range of 500 eV to 3 keV.

[0379] 82. A method of focusing a charged particle beam on a sample, the method comprising:

[0380] irradiating a sample disposed on a platform of a charged particle beam system using a charged particle beam;

[0381] adjusting a position of a first focus of the charged particle beam using the first component of the charged particle system and the reference sample; and

[0382] An electromagnetic field associated with the sample is manipulated by adjusting a first component of an electrical signal applied to a control electrode of the objective lens to form a second focus by adjusting a first focus of the charged particle beam on the sample.

[0383] 83. The method of clause 82, wherein adjusting the position of the first focus comprises adjusting the positioning of the platform on the Z-axis.

[0384] 84. The method of clause 83, wherein adjusting the positioning of the platform in the Z-axis comprises:

[0385] Using a height sensor to determine the positioning of the sample in the Z-axis; and

[0386] Based on the determined position of the sample, the position of the stage in the Z-axis is adjusted using the stage motion controller.

[0387] 85. The method of any of clauses 82-84, wherein the first component is configured to adjust a depth of focus of the charged particle beam with reference to the sample.

[0388] 86. A method according to any of clauses 82-85, wherein the first component is located upstream of a focusing component of an objective lens of the charged particle system, and wherein the first component comprises a charged particle source, an anode of a charged particle source, or a buncher lens.

[0389] 87. A method according to any of clauses 82-86, wherein the control electrode comprises a second component of the charged particle system and is located downstream of a focusing component of the objective of the charged particle system.

[0390] 88. The method of clause 87, wherein adjusting the electrical signal applied to the second component adjusts the landing energy of the charged particle beam on the sample.

[0391] 89. The method of clause 88, wherein the landing energy of the charged particle beam is in the range of 500 eV to 3 keV.

[0392] 90. A method according to any of clauses 87-89, wherein the second component of the charged particle system comprises one or more of a control electrode of the objective, the sample, or the stage.

[0393] 91. The method of any of clauses 87-90, wherein the first component of the charged particle system is different from the second component of the charged particle system.

[0394] 92. The method of any of clauses 82-91, wherein manipulating the electromagnetic field further comprises adjusting a second component of the electrical signal applied to the platform.

[0395] 93. The method of any of clauses 88-92, wherein the first component of the electric signal is determined based on an acceleration voltage and a landing energy of the charged particle beam.

[0396] 94. A method according to any one of clauses 92 and 93, wherein the first component of the electrical signal comprises a voltage signal having an absolute value in the range of 5 kV to 10 kV, and wherein the second component of the electrical signal comprises a voltage signal having an absolute value in the range of 0 V to 150 V.

[0397] 95. A method according to any one of clauses 92-94, wherein adjusting a first component of the electrical signal applied to the control electrode coarsely adjusts the first focus of the charged particle beam, and wherein adjusting a second component of the electrical signal applied to the platform, the reference sample, fine-tunes the first focus of the charged particle beam.

[0398] 96. The method of any of clauses 82-95, wherein manipulating the electromagnetic field further comprises adjusting a magnetic field configured to affect a characteristic of the charged particle beam.

[0399] 97. The method of clause 96, wherein the characteristic of the charged particle beam comprises at least one of a path, a direction, a velocity, or an acceleration of the charged particle beam.

[0400] 98. A charged particle beam system comprising:

[0401] a stage configured to hold a sample and movable along at least one of an XY axis or a Z axis; and

[0402] A controller having circuitry and configured to:

[0403] adjusting a position of a first focus of the charged particle beam using the first component of the charged particle system and the reference sample; and

[0404] An electromagnetic field associated with the sample is manipulated using a second component to form a second focus by adjusting the first focus of the charged particle beam with reference to the sample, wherein the second component is located downstream of a focusing component of an objective of the charged particle system.

[0405] 99. A system according to clause 98, wherein adjusting the position of the first focus includes adjusting the positioning of the platform on the Z axis.

[0406] 100. The system of any one of clauses 98 and 99, further comprising a position sensing system configured to determine a position of the sample in the Z-axis, wherein the position sensing system comprises a height sensor having a laser diode sensor assembly.

[0407] 101. The system of clause 100, wherein the controller is configured to adjust the positioning of the platform in the Z axis based on the positioning of the sample determined by the positioning sensing system.

[0408] 102. A system according to any of clauses 100 and 101, wherein the height sensor is configured to determine the position of the sample in the Z axis, and wherein the controller is configured to adjust the position of the platform in the Z axis to form a first focus of the charged particle beam on the sample.

[0409] 103. The system of any of clauses 98-102, wherein the first component is configured to adjust a depth of focus of the charged particle beam with reference to the sample.

[0410] 104. A system according to any of clauses 98-103, wherein the first component is located upstream of a focusing component of an objective lens of the charged particle system.

[0411] 105. The system of clause 104, wherein the first component comprises a charged particle source, an anode of a charged particle source, or a buncher lens, and wherein the first component of the charged particle system is different from the second component of the charged particle system.

[0412] 106. The method of any of clauses 98-105, wherein the manipulation of the electromagnetic field comprises adjustment of an electrical signal applied to the second component of the charged particle system.

[0413] 107. The system of any of clauses 98-106, wherein the second component of the charged particle system comprises one or more of a control electrode of the objective, the sample, or the stage.

[0414] 108. The system of any of clauses 106 and 107, wherein adjustment of the electrical signal applied to the second component adjusts the landing energy of the charged particle beam on the sample.

[0415] 109. The system of any of clauses 107 and 108, wherein the conditioning of the electrical signal comprises:

[0416] adjustment of a first component of an electrical signal applied to a control electrode of the objective lens; and

[0417] Modulation of the second component of the electrical signal applied to the platform.

[0418] 110. A system according to clause 109, wherein adjustment of the first component of the electrical signal applied to the control electrode coarsely adjusts the first focus of the charged particle beam, and wherein adjustment of the second component of the electrical signal applied to the platform fine-tunes the first focus of the charged particle beam.

[0419] 111. The system of any of clauses 98-110, wherein the controller is further configured to manipulate the electromagnetic field by adjusting a magnetic field configured to affect a characteristic of the charged particle beam.

[0420] 112. The system of clause 111, wherein the characteristic of the charged particle beam comprises at least one of a path, a direction, a velocity, or an acceleration of the charged particle beam.

[0421] 113. The system of any of clauses 110-112, wherein the first component of the electrical signal is determined based on an acceleration voltage and a landing energy of the charged-particle beam.

[0422] 114. A system according to any of clauses 110-113, wherein the first component of the electrical signal comprises a voltage signal having an absolute value in the range of 5kV to 10kV, and wherein the second component of the electrical signal comprises a voltage signal having an absolute value in the range of 0V to 150V.

[0423] 115. The system of any of clauses 109-114, wherein the landing energy of the charged particle beam is in the range of 500 eV to 3 keV.

[0424] 116. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of an apparatus to cause the apparatus to perform a method, wherein the apparatus comprises a charged particle source to generate a charged particle beam, and the method comprises:

[0425] adjusting a position of a first focus of the charged particle beam using the first component of the charged particle system and the reference sample; and

[0426] An electromagnetic field associated with the sample is manipulated using a second component to form a second focus by adjusting the first focus of the charged particle beam with reference to the sample, wherein the second component is located downstream of a focusing component of an objective lens of the charged particle system.

[0427] 117. The non-transitory computer-readable medium of clause 116, wherein the set of instructions executable by one or more processors of the device causes the device to further perform:

[0428] Using a height sensor to determine the positioning of the sample in the Z-axis; and

[0429] The positioning of the stage in the Z-axis is adjusted based on the determined position of the sample using a stage motion controller to form an initial focus of the charged particle beam on the sample.

[0430] 118. The non-transitory computer-readable medium of any of clauses 116 and 117, wherein the set of instructions executable by one or more processors of the device causes the device to further perform: manipulating an electromagnetic field associated with the sample by:

[0431] adjusting the first component of the electrical signal to coarsely adjust a first focus of the charged particle beam on the sample surface; and

[0432] A second component of the electrical signal to the stage is adjusted to fine tune a first focus of the charged particle beam on the sample surface.

[0433] 119. A method for generating a 3D image of a sample in a charged particle beam apparatus, the method comprising:

[0434] irradiating a sample disposed on a platform with a charged particle beam;

[0435] manipulating an electromagnetic field associated with the sample to adjust the focus of the charged particle beam with reference to the sample;

[0436] Based on the manipulation of electromagnetic fields, a plurality of focal planes are formed which are substantially perpendicular to the main optical axis of the charged particle beam;

[0437] generating a plurality of image frames from a plurality of focal planes of the sample, wherein image frames in the plurality of image frames are associated with corresponding focal planes in the plurality of focal planes; and

[0438] A 3D image of the sample is generated from the multiple image frames and corresponding focal plane information.

[0439] 120. The method of clause 119, wherein manipulating the electromagnetic field comprises adjusting a first component of an electrical signal applied to a control electrode of an objective lens of the charged particle beam device.

[0440] 121. The method of clause 120, wherein manipulating the electromagnetic field further comprises adjusting a second component of an electrical signal applied to a platform of the charged-particle beam device.

[0441] 122. The method of clause 121, wherein adjusting the second component of the electrical signal adjusts a landing energy of the charged particle beam on the sample.

[0442] 123. A method according to any one of clauses 121 and 122, wherein adjusting a first component of the electrical signal applied to the control electrode coarsely adjusts the first focus of the charged particle beam, and wherein adjusting a second component of the electrical signal applied to the platform, the reference sample, fine-tunes the first focus of the charged particle beam.

[0443] 124. A method according to any of clauses 121-123, wherein the first component of the electrical signal comprises a voltage signal having an absolute value in the range of 5kV to 10kV, and wherein the second component of the electrical signal comprises a voltage signal having an absolute value in the range of 0V to 150V.

[0444] 125. The method of any of clauses 122-124, wherein the landing energy of the charged particle beam is in the range of 500 eV to 3 keV.

[0445] 126. The method of any of clauses 119-125, further comprising forming a first focal plane of the plurality of focal planes that coincides with a top surface of the sample.

[0446] 127. The method of clause 126, further comprising forming a second focal plane of the plurality of focal planes at a distance below the first focal plane.

[0447] 128. The method of clause 127, wherein the distance between the first focal plane and the second focal plane is dynamically adjusted based on the material of the feature or sample being imaged.

[0448] 129. The method of any of clauses 119-128, further comprising generating a plurality of image frames at each of a plurality of focal planes of the sample.

[0449] 130. The method of any of clauses 119-129, wherein generating the 3D image comprises reconstructing the plurality of image frames using a reconstruction algorithm.

[0450] 131. A charged particle beam system comprising:

[0451] a stage configured to hold a sample and movable along at least one of an XY axis or a Z axis; and

[0452] A controller having circuitry configured to:

[0453] manipulating an electromagnetic field associated with the sample to adjust the focus of the charged particle beam with reference to the sample;

[0454] Based on the manipulation of electromagnetic fields, a plurality of focal planes are formed which are substantially perpendicular to the main optical axis of the charged particle beam;

[0455] generating a plurality of image frames from the plurality of focal planes, wherein image frames in the plurality of image frames are associated with corresponding focal planes in the plurality of focal planes; and

[0456] A 3D image of the sample is generated from the multiple image frames and corresponding focal plane information.

[0457] 132. The system of clause 131, wherein manipulating the electromagnetic field comprises adjusting a first component of an electrical signal applied to a control electrode of an objective lens of the charged particle beam system.

[0458] 133. The system of clause 132, wherein manipulating the electromagnetic field further comprises adjusting a second component of an electrical signal applied to a platform of the charged-particle beam system.

[0459] 134. The system of clause 133, wherein adjustment of the second component of the electrical signal adjusts a landing energy of the charged particle beam on the sample.

[0460] 135. A system according to any of clauses 133 and 134, wherein adjustment of the first component of the electrical signal applied to the control electrode coarsely adjusts the first focus of the charged particle beam, and wherein adjustment of the second component of the electrical signal applied to the platform fine-tunes the first focus of the charged particle beam.

[0461] 136. A system according to any of clauses 133-135, wherein the first component of the electrical signal comprises a voltage signal having an absolute value in the range of 5kV to 10kV, and wherein the second component of the electrical signal comprises a voltage signal having an absolute value in the range of 0V to 150V.

[0462] 137. The system of any of clauses 134-136, wherein the landing energy of the charged particle beam is in the range of 500 eV to 3 keV.

[0463] 138. The system of any of clauses 131-137, wherein the plurality of focal planes comprises a first focal plane that coincides with a top surface of the sample.

[0464] 139. A system according to clause 138, wherein the plurality of focal planes includes a second focal plane formed at a certain distance below the first focal plane.

[0465] 140. The system of clause 139, wherein a distance between the first focal plane and the second focal plane is dynamically adjusted based on a feature or sample material being imaged.

[0466] 141. The system of any of clauses 131-140, wherein the controller is further configured to generate a plurality of image frames at each of a plurality of focal planes of the sample.

[0467] 142. The system of any of clauses 131-141, wherein the controller is further configured to generate a 3D image of the sample by reconstructing the plurality of image frames using a reconstruction algorithm.

[0468] 143. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of an apparatus to cause the apparatus to perform a method, wherein the apparatus comprises a charged particle source to generate a charged particle beam, and the method comprises:

[0469] manipulating an electromagnetic field associated with the sample to adjust the focus of the charged particle beam with reference to the sample;

[0470] Based on the manipulation of electromagnetic fields, a plurality of focal planes are formed which are substantially perpendicular to the main optical axis of the charged particle beam;

[0471] generating a plurality of image frames from a plurality of focal planes of the sample, wherein image frames in the plurality of image frames are associated with corresponding focal planes in the plurality of focal planes; and

[0472] A 3D image of the sample is generated from the multiple image frames and corresponding focal plane information.

[0473] 144. The non-transitory computer-readable medium of clause 143, wherein the set of instructions executable by one or more processors of the device causes the device to further perform:

[0474] forming a first focal plane among the plurality of focal planes that coincides with the top surface of the sample; and

[0475] A second focal plane of the plurality of focal planes is formed at a predetermined distance below the first focal plane.

[0476] 145. A method of determining vibration of a charged particle beam apparatus, the method comprising:

[0477] detecting a first vibration of an electro-optical assembly configured to direct a charged particle beam toward a sample; and

[0478] detecting a second vibration of an electromechanical assembly configured to hold the sample; and

[0479] A vibration compensation signal is applied to the electro-optical component to compensate for the first vibration and the second vibration based on the determined vibration of the charged particle beam arrangement.

[0480] 146. The method of clause 145, further comprising adjusting a positioning of the sample with respect to one or more axes, wherein adjusting the positioning of the sample causes vibration of the electro-optical and electromechanical components.

[0481] 147. The method of any of clauses 145 and 146, wherein detecting the first vibration comprises detecting vibration of the electro-optical component about one or more axes using a first sensor.

[0482] 148. The method of clause 147, wherein the first sensor comprises an acceleration sensor mechanically coupled to the electro-optical assembly.

[0483] 149. The method of clause 148, wherein the acceleration sensor comprises a piezoelectric sensor, a capacitive accelerometer, a microelectromechanical system (MEMS)-based accelerometer, or a piezoresistive accelerometer.

[0484] 150. The method of any of clauses 147-149, wherein the first sensor is configured to generate a voltage signal based on a frequency of the detected first vibration.

[0485] 151. The method of any of clause 150, wherein detecting a second vibration comprises detecting vibration of the electromechanical component in a translational axis and a rotational axis through use of a second sensor.

[0486] 152. The method of clause 151, wherein the second sensor comprises a plurality of position sensors, the electro-optical position sensors being configured to generate a displacement signal based on a frequency of the detected second vibration.

[0487] 153. The method of clause 152, wherein a first positioning sensor of the plurality of positioning sensors is configured to detect vibration of the electromechanical component on a translational axis, and wherein a second positioning sensor of the plurality of positioning sensors is configured to detect vibration of the electromechanical component on a rotational axis.

[0488] 154. A method according to any of clauses 152-153, further comprising:

[0489] receiving a voltage signal and a displacement signal through a first controller;

[0490] Using a first controller, a vibration compensation signal is determined based on the received voltage signal and the displacement signal.

[0491] 155. The method of clause 154, wherein determining the vibration compensation signal comprises:

[0492] identifying a plurality of vibration patterns based on information associated with the first vibration and the second vibration;

[0493] estimating vibrations of the electro-optical and electromechanical components based on the identified plurality of vibration modes;

[0494] determining vibrations in a plurality of axes based on the estimated vibrations of the electro-optical and electromechanical components; and

[0495] A vibration compensation signal is determined based on the determined vibrations in the plurality of axes.

[0496] 156. The method of any of clauses 145-155, wherein the vibration compensation signal is determined to compensate for the vibration based on an estimate of the predicted vibration for a future time with reference to the measurement times of the first vibration and the second vibration.

[0497] 157. The method of any of clauses 155 and 156, wherein identifying a plurality of vibration patterns comprises converting a voltage signal into a corresponding distance signal.

[0498] 158. The method of any of clauses 155-157, wherein identifying the plurality of vibration modes further comprises decoupling the second vibration of the electromechanical assembly from the vibration of a housing of the electromechanical assembly.

[0499] 159. The method of any of clauses 155-158, wherein estimating vibrations of the electro-optical and electromechanical components comprises using a simulation model.

[0500] 160. The method of clause 159, wherein the simulation model comprises a three-dimensional finite element analysis model (3D-FEM), a finite difference analysis model (FDM), or a mathematical analysis model.

[0501] 161. The method of clauses 154-160, further comprising receiving the determined vibration compensation signal by a second controller.

[0502] 162. The method according to clause 161, further comprising:

[0503] receiving, by a second controller, a beam scanning signal; and

[0504] A modified beam scanning signal is generated by a second controller based on the received beam scanning signal and the received vibration compensation signal.

[0505] 163. The method of clause 162, further comprising generating, by a signal generator, a beam deflection signal based on the modified beam scanning signal.

[0506] 164. A method according to clause 163, wherein the beam deflection signal is applied to the electro-optical component and is used to adjust the characteristics of the charged particle beam incident on the sample.

[0507] 165. A method according to any of clauses 163 and 164, wherein the beam deflection signal is applied to a beam deflection controller associated with the electro-optical component.

[0508] 166. The method of any of clauses 164 and 165, wherein the characteristic of the charged particle beam comprises a beam scanning speed, a beam scanning frequency, a beam scanning duration, or a beam scanning range.

[0509] 167. The method of any of clauses 158-166, wherein a plurality of positioning sensors are disposed on a surface of a housing of the electromechanical assembly.

[0510] 168. A method according to any of clauses 145-167, wherein the electro-optical component comprises a charged particle column, and wherein the electromechanical component comprises a stage configured to hold a sample and capable of movement in one or more of an X, Y or Z axis.

[0511] 169. A charged particle beam system comprising:

[0512] a first sensor configured to detect a first vibration of an electro-optical component of the charged particle beam system;

[0513] a second sensor configured to detect a second vibration of an electromechanical component of the charged-particle beam system; and

[0514] A first controller includes circuitry to generate a vibration compensation signal based on the detected first and second vibrations applied to the electro-optical component.

[0515] 170. The system of clause 169, wherein the electro-optical assembly comprises a charged particle column and is configured to direct the charged particle beam toward the sample.

[0516] 171. The system of clause 170, wherein the electromechanical assembly comprises a platform configured to hold a sample and capable of moving in one or more of an X, Y, or Z axis.

[0517] 172. The system of any of clauses 170 and 171, wherein adjustment of the positioning of the sample causes vibration of the electro-optical and electromechanical components.

[0518] 173. The system of any of clauses 169-172, further comprising a housing configured to house electromechanical components of the charged-particle beam device.

[0519] 174. A system according to clause 173, wherein the electromechanical assembly is mechanically coupled to the shell such that the moving platform causes vibration of the shell.

[0520] 175. The system of any of clauses 173 and 174, wherein the electro-optical assembly is mechanically coupled to the housing such that vibration of the housing causes a first vibration of the electro-optical assembly.

[0521] 176. The system of any of clauses 169-175, wherein the first sensor is further configured to detect a first vibration of the electro-optical component about one or more axes.

[0522] 177. The system of any of clauses 169-176, wherein the first sensor comprises an acceleration sensor mechanically coupled to the electro-optical assembly.

[0523] 178. The system of clause 177, wherein the acceleration sensor comprises a piezoelectric sensor, a capacitive accelerometer, a microelectromechanical system (MEMS)-based accelerometer, or a piezoresistive accelerometer.

[0524] 179. The system of any of clauses 169-178, wherein the first sensor is configured to generate a voltage signal based on a frequency of the detected first vibration.

[0525] 180. The system of any of clause 179, wherein the second sensor is configured to detect a second vibration of the electromechanical component in a translational axis and a rotational axis.

[0526] 181. The system of any of clauses 179 and 180, wherein the second sensor comprises a plurality of position sensors configured to generate a displacement signal based on a frequency of the detected second vibration.

[0527] 182. A system according to clause 181, wherein a first positioning sensor of the plurality of positioning sensors is configured to detect vibration of the electromechanical component on a translational axis, and wherein a second positioning sensor of the plurality of positioning sensors is configured to detect vibration of the electromechanical component on a rotational axis.

[0528] 183. The system of clause 182, wherein the first positioning sensor and the second positioning sensor are disposed on a surface of a housing of the electromechanical assembly.

[0529] 184. The system of any of clauses 181-183, wherein the first controller is further configured to:

[0530] receiving a voltage signal and a displacement signal; and

[0531] A vibration compensation signal is determined based on the voltage signal and the displacement signal.

[0532] 185. The system of any of clauses 169-184, wherein the first controller comprises circuitry to:

[0533] identifying a plurality of vibration patterns based on information associated with the first vibration and the second vibration;

[0534] estimating vibrations of the electro-optical and electromechanical components based on the identified plurality of vibration modes;

[0535] determining vibrations in a plurality of axes based on the estimated vibrations of the electro-optical and electromechanical components; and

[0536] A vibration compensation signal is determined based on the determined vibrations on the plurality of axes.

[0537] 186. The system of any of clauses 169-185, wherein the vibration compensation signal is determined to compensate for the vibration based on an estimate of a predicted vibration for a future time with reference to the measured times of the first vibration and the second vibration.

[0538] 187. The system of any of clauses 185 and 186, wherein the identification of the plurality of vibration patterns comprises conversion of a voltage signal into a corresponding distance signal.

[0539] 188. The system of any of clauses 185-187, wherein the identification of the plurality of vibration modes further comprises decoupling the second vibration of the electromechanical assembly from the vibration of the housing of the electromechanical assembly.

[0540] 189. A system according to any of clauses 184-188, wherein the estimation of vibrations of the electro-optical and electromechanical components comprises the use of simulation models.

[0541] 190. A system according to clause 189, wherein the simulation model comprises a three-dimensional finite element analysis model (3D-FEM), a finite difference analysis model (FDM), or a mathematical analysis model.

[0542] 191. The system of any of clauses 184-190, further comprising a second controller comprising circuitry to receive the determined vibration compensation signal.

[0543] 192. The system of clause 191, wherein the second controller comprises circuitry to:

[0544] receiving a beam scanning signal; and

[0545] A modified beam scanning signal is generated based on the received beam scanning signal and the vibration compensation signal.

[0546] 193. The system of clause 192, further comprising a signal generator configured to generate a beam deflection signal based on the modified beam scanning signal.

[0547] 194. The system of clause 193, wherein the beam deflection signal is applied to the electro-optical component and is configured to adjust characteristics of the charged particle beam incident on the sample.

[0548] 195. A system according to any of clauses 193 and 194, wherein the beam deflection signal is applied to a beam deflection controller associated with the electro-optical component.

[0549] 196. The system of any of clauses 194 and 195, wherein the characteristic of the charged particle beam comprises a beam scanning speed, a beam scanning frequency, a beam scanning duration, or a beam scanning range.

[0550] 197. A non-transitory computer-readable medium comprising a set of instructions, the set of instructions being executable by one or more processors of an apparatus to cause the apparatus to perform a method of determining vibration of a charged particle beam apparatus, the method comprising:

[0551] detecting a first vibration of an electro-optical assembly configured to direct a charged particle beam toward a sample; and

[0552] detecting a second vibration of an electromechanical assembly configured to hold the sample; and

[0553] A vibration compensation signal is applied to the electro-optical component to compensate for the first vibration and the second vibration based on the determined vibration of the charged particle beam arrangement.

[0554] 198. A non-transitory computer-readable medium according to claim 197, wherein the set of instructions capable of being executed by one or more processors of the device causes the device to further perform: adjusting the positioning of the sample with reference to one or more axes, wherein adjusting the positioning of the sample causes vibration of the electro-optical component and the electromechanical component.

[0555] 199. The non-transitory computer-readable medium of any of clauses 197 and 198, wherein the set of instructions executable by one or more processors of the device causes the device to further perform: determining a vibration compensation signal based on the voltage signal and the displacement signal, the determining comprising the steps of:

[0556] identifying a plurality of vibration patterns based on information associated with the first vibration and the second vibration;

[0557] estimating vibrations of the electro-optical and electromechanical components based on the identified plurality of vibration modes;

[0558] determining vibrations in a plurality of axes based on the estimated vibrations of the electro-optical and electromechanical components; and

[0559] A vibration compensation signal is determined based on the determined vibrations on the plurality of axes.

[0560] 200. The non-transitory computer-readable medium of any of clauses 197-199, wherein the set of instructions executable by one or more processors of the apparatus causes the apparatus to further perform:

[0561] receiving a beam scanning signal via a controller;

[0562] generating a modified beam scanning signal based on the received beam scanning signal and the vibration compensation signal;

[0563] generating, by a signal generator, a beam deflection signal based on the modified beam scanning signal, wherein the beam deflection signal is applied to the electro-optical assembly and is configured to adjust a characteristic of the charged particle beam incident on the sample; and

[0564] A beam deflection signal is applied to a beam deflection controller associated with the electro-optical assembly.

[0565] A non-transitory computer-readable medium may be provided that stores instructions for a processor (e.g., a processor of the controller 109, the processor 430) to perform wafer inspection, wafer imaging, stage calibration, displacement error calibration, displacement error compensation, manipulation of electromagnetic fields associated with a sample, communication with an image acquisition system, activation of an acceleration sensor, activation of a laser interferometer, operation of a DVEC, execution of an algorithm to estimate vibrations of an SEM column and stage, operation of a charged particle beam device or other imaging equipment, etc. Common forms of non-transitory media include, for example, a floppy disk, a flexible magnetic disk, a hard disk, a solid-state drive, a magnetic tape or any other magnetic data storage medium, a compact disc-read only memory (CD-ROM), any other optical data storage medium, any physical medium having a pattern of holes, a random access memory (RAM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a Flash-EPROM or any other flash memory, a non-volatile random access memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions thereof.

[0566] The block diagrams in the accompanying drawings illustrate the structure, function and operation of possible implementations of the systems, methods and computer hardware or software products according to various exemplary embodiments of the present disclosure. To this end, each box in the flowchart or block diagram may represent a module, segment or code portion comprising one or more executable instructions for implementing a specified logical function. It should be understood that in some alternative implementations, the functions indicated in the box may occur in an order different from that indicated in the accompanying drawings. For example, two boxes shown in succession may be executed or implemented substantially simultaneously, or, depending on the functions involved, the two boxes may sometimes be executed in the opposite order. Some boxes may also be omitted. It should also be understood that each box in the block diagram and the combination of boxes may be implemented by a dedicated hardware-based system that performs the specified function or action, or by a combination of dedicated hardware and computer instructions.

[0567] It should be understood that the embodiments of the present disclosure are not limited to the exact construction that has been described above and illustrated in the drawings, and that various modifications and changes may be made without departing from the scope of the present disclosure.

Claims

1. A charged particle beam system comprising: a stage configured to hold a sample and capable of moving in XY and Z axes; a position sensing system configured to determine lateral and vertical displacements of the platform; as well as The controller is configured as: applying a first signal to deflect a primary charged particle beam incident on the sample to at least partially compensate for the lateral displacement of the stage; as well as A second signal is applied to adjust a focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the stage, wherein the vertical displacement corresponds to a difference between a target position of the stage on the Z axis and a current position of the stage. 2 . The system of claim 1 , wherein the first signal comprises an electrical signal that affects how the primary charged particle beam is deflected in at least one of an XY axis. 3 . The system of claim 2 , wherein the electrical signal comprises a signal having a bandwidth in the range of 10 kHz to 50 kHz.

4. The system of claim 1 , wherein the lateral displacement corresponds to a difference between a target position of the platform and a current position of the platform in at least one of the XY axes. 5 . The system of claim 1 , wherein the controller is further configured to dynamically adjust at least one of the first signal or the second signal during scanning of the primary charged particle beam over the sample.

6. The system of claim 1, wherein the second signal comprises a voltage signal applied to the stage, the voltage signal affecting how a deflected charged particle beam incident on the sample is focused on the Z-axis. 7 . The system of claim 6 , wherein the voltage signal comprises a signal having a bandwidth in the range of 50 kHz to 200 kHz.

8. The system of claim 1, wherein the vertical displacement varies during scanning of the primary charged particle beam across the sample to at least partially compensate for angular rotation about at least one of an X or Y axis.

9. The system of claim 1, further comprising a platform motion controller, wherein the platform motion controller comprises a plurality of motors configured to be independently controlled by a third signal.

10. The system of claim 9, wherein each of the plurality of motors is independently controlled to adjust the leveling of the platform so that the platform is substantially perpendicular to the optical axis of the primary charged particle beam. 11 . The system of claim 9 , wherein the third signal comprises a plurality of control signals, each control signal of the plurality of control signals corresponding to at least one motor of the plurality of motors.

12. The system of claim 9, wherein the plurality of motors comprises piezoelectric motors.

13. The system of claim 9, wherein the plurality of motors comprise piezoelectric actuators.

14. The system of claim 9, wherein the plurality of motors comprises ultrasonic piezoelectric motors.

15. The system of claim 11, further comprising: a first component configured to form an embedded control signal based on the plurality of control signals; as well as A second component is configured to extract at least one control signal of the plurality of control signals from the embedded control signal.

16. The system of claim 10, wherein adjusting the leveling of the platform is based on a geometric model of an actuation output of the platform.

17. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of a device to cause the device to perform a method, wherein the device comprises a charged particle source to generate a primary charged particle beam, and the method comprises: determining a lateral displacement of a platform, wherein the platform is movable in X, Y, and Z axes; A controller is instructed to apply a first signal to deflect a primary charged particle beam incident on the sample to at least partially compensate for the lateral displacement, and to apply a second signal to adjust the focus of the deflected charged particle beam incident on the sample to at least partially compensate for the vertical displacement of the platform, wherein the vertical displacement corresponds to a difference between a target position of the platform on the Z-axis and a current position of the platform.

Images