Method for inspecting samples and multi-electron beam inspection system

Abstract

A method for inspecting a sample using a multi-electron beam inspection system (100) is described. The method comprises the steps of: placing a sample on a movable stage (110) extending in an XY plane; generating a plurality of electron beams (105) propagating toward the sample; focusing the plurality of electron beams on the sample at a plurality of probe positions (106) in a two-dimensional array; scanning the surface of the sample by moving the movable stage in a predetermined scanning pattern while maintaining the plurality of electron beams in a stationary state; and detecting signal electrons emitted from the sample during the movement of the movable stage to inspect the sample. Additionally, a multi-electron beam inspection system (100) for inspecting a sample according to the above method is described.

Description

Technology Field

[0001] The present disclosure relates to a method and system for inspecting a sample using charged particle beams. More specifically, the embodiments described herein relate to the inspection of a sample using a plurality of electron beams in parallel. In particular, the embodiments relate to methods for inspecting a sample using a multi-electron beam inspection system for inspecting, for example, semiconductor wafers or other substrates, and to multi-electron beam inspection systems for high-speed inspection of samples using high resolution. Background Technology

[0002] Charged particle beam devices, particularly electron microscopes, have many functions in multiple industrial fields, including (but not limited to) critical dimensioning of semiconductor devices during manufacturing, defect inspection of semiconductor devices, inspection and imaging of semiconductor devices, exposure systems for lithography, detection devices, and test systems, such as electron beam inspection systems. Consequently, there is a high demand for structuring, testing, and inspecting samples at micrometer and nanometer scales.

[0003] Process control, inspection, or structuring at the micrometer and nanometer scales is often performed using charged particle beam devices, such as electron microscopes, which generate and focus charged particle beams, particularly electron beams. Due to their short wavelengths, charged particle beams provide superior spatial resolution compared to, for example, photon beams.

[0004] In many applications, samples are inspected to monitor their quality. For example, wafers or glass substrates upon which layers of electronic devices and / or coating materials are deposited are manufactured for the display market or to produce electronic chips or integrated die packages. Since defects can occur during sample processing, such as during coating, inspecting the samples to review defects and monitor quality can be beneficial. Additionally, the size, shape, and relative position of structures generated by any patterning process need to be monitored and controlled.

[0005] For example, inspecting samples with high resolution within the nanometer range using a scanning electron microscope is time-consuming. To increase sample throughput, only selected regions of the sample, such as those containing, on average, more defects than other regions, may be inspected. Alternatively, to increase throughput, only random sub-sections of the samples may be inspected.

[0006] Another approach to increasing throughput is parallel inspection of samples using multiple electron beams simultaneously. For example, a multi-electron beam inspection system may include multiple inspection columns to inspect samples at higher speeds, but typically with reduced resolution.

[0007] Samples are typically inspected by using scan deflectors to scan one or more electron beams of a scanning electron microscope (SEM) system across the sample surface and then moving the sample to position different parts of the sample within the SEM's field of view. However, SEMs equipped with scan deflectors are complex, large, and expensive devices.

[0008] Considering the above, it would be very beneficial to provide electron beam inspection methods and systems for rapidly and reliably inspecting samples, such as wafers or large-area substrates, with high resolution.

[0009] In light of the above, a method for inspecting a sample using a multi-electron beam inspection system and multi-electron beam inspection systems are provided. Further aspects, advantages, and features of the present disclosure are apparent from the detailed description and the accompanying drawings.

[0010] According to one aspect, a method for inspecting a sample is provided. The method comprises: placing a sample on a movable stage extending in an XY-plane; generating a plurality of electron beams that propagate toward the sample; focusing the plurality of electron beams onto the sample at a plurality of probe positions arranged in a two-dimensional array; scanning the sample by moving the movable stage in a predetermined scanning pattern while maintaining the plurality of electron beams in a stationary state; and detecting signal electrons emitted from the sample during the scanning step to inspect the sample. In some embodiments, the plurality of electron beams may propagate toward the sample essentially parallel to each other.

[0011] According to another aspect, a multi-electron beam inspection system is provided. The multi-electron beam inspection system is configured to perform the sample inspection methods described herein. In particular, the multi-electron beam inspection system may include a movable stage extending in an XY-plane for placing a sample on top of itself, and a plurality of inspection columns configured to generate a plurality of electron beams and to focus a plurality of electron beams onto the sample at a plurality of probe positions arranged in a two-dimensional array. Each of the plurality of inspection columns includes a beam emitter, a focusing lens, and a detector for detecting signal electrons. The multi-electron beam inspection system further includes a stage controller configured to move the movable stage in a predetermined scanning pattern during the inspection of the sample while maintaining the plurality of electron beams in a stationary state. In some embodiments, the plurality of inspection columns may be configured to generate a plurality of electron beams such that the plurality of electron beams propagate toward the sample in essentially parallel to each other.

[0012] Multiple inspection columns may be static electron beam microcolumns without scan deflectors, configured to provide static electron beams while a movable stage moves in a scanning pattern to scan a sample.

[0013] According to another aspect, a multi-electron beam inspection system is provided. The system comprises a plurality of inspection columns without scan deflectors arranged in a two-dimensional array in the X-direction and Y-direction and facing a movable stage for placing a sample on top of itself, and a stage controller configured to move the movable stage in the XY-plane in a predetermined scanning pattern.

[0014] The embodiments also relate to assemblies for carrying out the disclosed methods and include assembly parts for carrying out each described aspect of the method. These aspects of the method may be carried out through hardware components, through a computer programmed by appropriate software, by any combination of the two, or in any other way. Furthermore, the embodiments according to the present disclosure also relate to methods for operating the described assemblies and methods for manufacturing the described systems. Methods for operating the described assemblies include aspects of the method for carrying out each and every function of the assembly. Brief explanation of the drawing

[0015] In a manner that the features of the above-mentioned disclosure can be understood in detail, a more detailed description of the disclosure briefly summarized above may be made by reference to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings should not be construed as limiting, as they only illustrate exemplary embodiments. A complete and possible disclosure is presented to those skilled in the art in more detail in the remainder of this specification, including reference to the accompanying drawings, in which: FIG. 1 is a schematic cross-sectional view of a multi-electron beam inspection system according to embodiments described herein; FIG. 2a is a schematic plan view of a multi-electron beam inspection system according to embodiments described herein; FIG. 2b illustrates a sample to be examined to illustrate the examination method described herein; FIG. 3 illustrates a schematic cross-sectional view of an inspection column of a multi-electron beam inspection system according to embodiments described herein; and FIG. 4 illustrates a flowchart illustrating a method of inspecting a sample using a multi-electron beam inspection system according to the embodiments described herein. Specific details for implementing the invention

[0016] Now, various exemplary embodiments will be referenced in detail, and one or more examples of such various exemplary embodiments are illustrated in each drawing. Each example is provided by way of description and is not to be construed as a limitation. For example, features illustrated or described as part of one embodiment may be used with respect to or in conjunction with other embodiments to yield additional embodiments. The present disclosure is intended to include such modifications and variations.

[0017] In the following description of the drawings, identical reference numbers refer to identical components. Only differences between individual embodiments are described. The structures depicted in the drawings are not necessarily depicted to actual scale, but rather provide a better understanding of the embodiments.

[0018] The embodiments described herein relate to multi-electron beam inspection systems for inspecting a sample using a plurality of electron beams in parallel. In multi-electron beam inspection systems, a plurality of primary electron beams or beamlets are generated and focused onto a sample to be inspected. When the primary electron beams hit the surface of the sample, signal electrons are emitted from the sample. The signal electrons are detected using one or more detectors to acquire spatial information about the sample. The sample may be imaged or inspected in another manner.

[0019] Signal electron detection may include the detection of secondary electrons (SE), i.e., signal electrons generated in a sample when struck by primary electrons (PE), and / or backscattered electrons (BSE), i.e., primary electrons backscattered from the sample at various scattering angles. While secondary electrons may typically be low-energy electrons in an energy range of several eV to tens of eV, backscattered electrons may have particle energies of several keV, e.g., 1 keV to 30 keV or more.

[0020] In conventional multi-electron beam inspection systems, primary electron beams are scanned across the sample surface using scan deflectors arranged in individual inspection columns. However, multi-electron beam inspection systems with multiple scanning electron microscopes are typically complex and expensive, and individual scanning electron microscopes are space-consuming. For this reason, such systems typically include only a limited number of inspection columns, which ultimately limits the increase in inspection speed.

[0021] In modern electron beam inspection systems, it is becoming increasingly important to inspect samples, such as semiconductor wafers, very quickly, accurately, and with high resolution. These objectives can be achieved using a multi-electron beam inspection system according to the embodiments described herein.

[0022] FIG. 1 illustrates a schematic cross-sectional view of a multi-electron beam inspection system (100) (hereinafter referred to as "system (100)") for inspecting a sample (10) according to embodiments described herein. The system (100) includes a movable stage (110) for placing the sample (10) on top of it, and a plurality of inspection columns (130). The sample support surface of the movable stage (110) extends in the XY-plane. Accordingly, when a flat sample, such as a wafer or a glass substrate, is placed on the movable stage (110), the main surface of the sample (10) extends in the XY-plane, and the plurality of inspection columns (130) face the sample. The movable stage (110) is movable in two transverse directions in the XY-plane, e.g., the X-direction (exemplarily illustrated as the horizontal direction in FIG. 1) and the Y-direction perpendicular to the X-direction (exemplarily illustrated as the direction perpendicular to the paper plane in FIG. 1). Alternatively or additionally, the movable stage (110) may be rotatable so that the sample can be rotated about an axis (θ-movement).

[0023] The movable stage (110) may additionally be movable in the Z-direction, i.e., toward the plurality of inspection columns (130) and away from the plurality of inspection columns (130), for example, to position the sample surface on the focal plane of the plurality of inspection columns (130) or to adapt the operating distance of the system.

[0024] A plurality of inspection columns (130) are configured to generate a plurality of electron beams (105). As schematically depicted in FIG. 1, the plurality of electron beams (105) propagate essentially parallel to each other toward a sample (10) placed on a movable stage (110). Each of the plurality of inspection columns (130) defines an optical axis (138), and along this optical axis (138), individual electron beams of the plurality of electron beams propagate toward the sample (10). The system (100) is configured to focus the plurality of electron beams onto the sample at a plurality of probe positions (106), and the probe positions (106) are arranged in a two-dimensional array.

[0025] In the cross-sectional view of FIG. 1, only probe positions arranged side by side in the X-direction are shown. However, it should be understood that the two-dimensional array formed by a plurality of probe positions (106) on the sample extends in two transverse directions in the XY-plane, as schematically depicted in FIG. 2a.

[0026] In particular, a plurality of inspection columns (130) may be arranged in a two-dimensional array extending in two transverse directions, as schematically illustrated in FIG. 2a, which illustrates the system in a plan view. A "two-dimensional array" as used herein may be understood as an array of inspection columns in which the inspection columns are arranged side by side along a single line in cross-sectional planes perpendicular to the optical axis (138) ("one-dimensional array"), as well as along two or more adjacent lines or in different two-dimensional patterns of inspection columns. Accordingly, a plurality of probe positions (106) at which electron beams generated from the plurality of inspection columns (130) strike the sample form a two-dimensional pattern of beam spots on the sample surface in the XY-plane (see FIG. 2a).

[0027] Returning to FIG. 1, each of the plurality of inspection columns (130) may include a beam emitter (131) for providing an electron beam, a focusing lens (132) for focusing the electron beam onto a sample at a probe position, and a detector (133) for detecting signal electrons emitted by the sample when the electron beam strikes the sample.

[0028] In typical embodiments, the plurality of inspection columns (130) do not include any scan deflectors for scanning electron beams across the sample surface during sample inspection. Therefore, the inspection columns (130) described herein may also be referred to as "static electron beam micro-columns," which are different from conventionally used scanning electron beam columns. A static electron beam micro-column can be understood as an electron beam inspection column configured for sample inspection using a static electron beam, i.e., sample inspection without beam scanning using a scan deflector, i.e., sample inspection performed by moving the sample in a scanning pattern against the static electron beam.

[0029] The system (100) further includes a stage controller (180) configured to move a movable stage (110) in a predetermined scanning pattern during the inspection of a sample while maintaining a plurality of electron beams in a stationary state. Accordingly, the sample (10) is inspected by exclusively moving the movable stage (110) in a predetermined scanning pattern for the static electron beams. The stage movement causes the scanning of the stationary electron beams across the surface of the sample in a predetermined scanning pattern. The electron beams may be maintained in a stationary state throughout the entire inspection of the sample.

[0030] As a result, multiple inspection columns (130) can be constructed very small and relatively inexpensively. A large number of inspection columns (130) can be provided as an array, for example, more than 10 inspection columns, particularly more than 50 inspection columns, more particularly more than 100 inspection columns, or even more than 150 inspection columns. The number of inspection columns may depend on the size of the sample to be inspected. For example, a system configured to inspect wafers with a diameter of 300 mm may include more than 100 to less than 200 inspection columns. A system configured to inspect wafers with a diameter of 450 mm may include much more inspection columns.

[0031] In some embodiments, each inspection column includes a beam emitter (131), a focusing lens (132), and optionally a beam corrector (shown in FIG. 3), such as a stigmator. In some embodiments, additional beam influence elements for affecting primary electron beams are not provided in the inspection columns. In other embodiments, a beam deflector unit (not shown) may optionally be provided in the inspection columns for tuning and / or alignment purposes of the electron beam. However, inspection columns typically do not include a scan deflector for scanning the electron beam across the sample to inspect the sample.

[0032] In some embodiments, the focusing lens may be an electrostatic lens, such as an electrostatic multipole lens, such as an octupole lens. Since electrostatic lenses are small and easy to implement, many inspection rows can be provided side by side at close distances.

[0033] The beam emitter may include an electron source, such as a cold field emitter, a thermionic emitter, a Schottky-type emitter, or other emitters configured to provide an electron beam. For example, the beam emitter may include a tip for emitting electrons and an extraction electrode.

[0034] Multiple inspection columns include detectors for detecting signal electrons released from a sample. The detector (133) may be configured to detect any of secondary electrons (SE) and backscattered electrons (BSE), and / or may include any one or more of a scintillator, PIN diode, multichannel plate, and Everhard-Thornley detector. In some embodiments, each inspection column may be provided with a separate detector for detecting backscattered electrons and / or secondary electrons generated by an individual electron beam. In some embodiments, the detector has a detector surface having an opening surrounding the optical axis (138) of the inspection columns, through which the primary electron beam propagates. The distance between the movable stage (110) and the detector (133) may be 1 mm or more and 1 cm or less in some embodiments.

[0035] Each of the plurality of inspection columns (130) may include an individual vacuum chamber (also referred to herein as a “microscope chamber (102”)) so that the internal space of each inspection column can be evacuated. The microscope chamber (102) may house the beam-optical elements of the individual inspection column, in particular the beam emitter (131) and the focusing lens (132). The interior of the microscope chamber (102) is maintained at an ultra-high vacuum during the operation of the inspection column, for example, 1×10⁻⁶ -8It can be pumped down to a pressure of mbar or less. Alternatively, two or more of the multiple inspection columns (130), particularly all of the inspection columns, may include a single microscope chamber (not shown) housing multiple beam emitters and focusing lenses. By evacuating the single microscope chamber, the interior of the multiple inspection columns can be evacuated, and an ultra-high vacuum can be provided during inspection.

[0036] In some embodiments, a movable stage (110) for positioning a sample on top of itself may be provided in the sample chamber (101). The sample chamber (101) is kept under high vacuum during the operation of the system, for example, 1×10 -2 It can be pumped down to a pressure of mbar or less. One or more microscope chambers (102) may protrude into the sample chamber (101) such that the individual front ends of a plurality of inspection columns (130) are oriented toward the movable stage (110). The “working distance (WD)” of the system as used herein may be understood as the distance between the front ends of the microscope chambers (102) (or the lowest mechanical thermal surface) and the sample (10) during inspection. Sample inspection according to the embodiments described herein may be performed at a working distance of 1 mm or more and 5 mm or less.

[0037] A plurality of inspection columns (130) may be configured to inspect a sample with a resolution of 20 nm or less, particularly 10 nm or less, or even 5 nm or less. In particular, a plurality of inspection columns (130) may be configured to focus a plurality of electron beams such that electron beam probes having diameters of 20 nm or less, particularly 10 nm or less, are provided on the sample surface at a plurality of probe positions (106).

[0038] In some embodiments, a plurality of inspection columns (130) are arranged in a two-dimensional array of inspection columns, and the two-dimensional array comprises an array of A × B inspection columns extending in two transverse directions, wherein A and B are integers greater than or equal to 5, particularly greater than or equal to 10. For example, 10 × 10 inspection columns may be provided as a closely packed array. In particular, as schematically depicted in FIG. 2a, the essentially whole surface of the movable stage in the plan view may be "covered" by the inspection columns. The optical axes of adjacent inspection columns of the array may be arranged close to each other, for example, at distances (135) of 5 cm or less.

[0039] The sample (10) can be inspected using the multi-electron beam inspection system (100) of FIG. 1 in the following manner:

[0040] First, a sample (10) may be placed on a movable stage (110). For example, the sample (10) may be a wafer, such as a semiconductor wafer to be inspected. In other embodiments, the sample (10) may include a die package comprising two or more interconnected dies. Specifically, the sample may include an interconnection between two or more packaged dies that can be connected by advanced packaging. In additional embodiments, the sample (10) may be a substrate, such as a large-area glass substrate having one or more layers to be inspected deposited on top, such as a substrate for manufacturing displays. The large-area substrate may have a surface area of ​​1 m² or more. The surface of the sample may extend in an XY-plane defined by the movable stage (110).

[0041] A plurality of electron beams (105) are generated that propagate essentially parallel to each other toward a sample (10). The plurality of electron beams (105) are focused on the sample at a plurality of probe positions (106), and the plurality of probe positions (106) are arranged in a two-dimensional array in the XY-plane.

[0042] The movable stage (110) is moved to a predetermined scanning pattern to scan the sample, while a plurality of electron beams are maintained in a static state. During the stage scanning for inspecting the sample, signal electrons emitted from the sample are detected.

[0043] The movable stage (110) can be controlled by a stage controller (180), wherein the stage controller can be configured to position the stage with the assistance of an interferometer (i.e., an X / Y interferometer) configured to determine the stage position with an accuracy of 20 nm or less, particularly 10 nm or less, or even 5 nm or less, and accordingly, to determine the stage position particularly in the X-direction and / or Y-direction. Thus, the movable stage can be moved with high accuracy in a predetermined scanning pattern. In some embodiments, the stage can be interferometer-controlled. A laser interferometer may be specifically provided for monitoring the stage position with an accuracy of 10 nm or less, particularly 5 nm or less, particularly in the X-direction and Y-direction. The current stage position can be forwarded to a test controller that receives and evaluates signals from one detector (133) or all detectors of a plurality of test columns. To generate an image of the sample and / or detect sample defects with high resolution, the current coordinates of the movable stage, as determined by the secondary electronic signal versus stage controller (180), may be recorded. By transmitting the signals of all detectors to a single inspection controller, an image of the intact sample may, if desired, be composed of individual detector signals.

[0044] Accordingly, the resulting image resolution provided by the inspection system results in an image resolution of 10 nm or less, based on both the first beam resolution (spot size) (Upe) (wherein the spot size is typically 20 nm or less) and the stage position accuracy reading by the interferometer (wherein the spot size is typically 10 nm or less).

[0045] When a plurality of electron beams (105) provide beam probes having probe diameters of 20 nm or less (or 10 nm or less) on a sample, and the stage position is monitored with an accuracy of 10 nm or less (or 5 nm or less) and transmitted to an inspection controller, it is possible to inspect the sample with a resolution of 10 nm or less (or 5 nm or less). Much better resolutions are possible.

[0046] In some embodiments, a plurality of 10 or more electron beams, particularly 50 or more electron beams, or even 100 or more electron beams are generated and focused onto a sample. Accordingly, the inspection speed can be increased by 50 or 100 times compared to a one-beam inspection system, and at the same time, high-resolution inspection of the sample surface within the nm scale is possible. To provide an example: in a one-beam inspection system, inspection of a surface area of ​​1 cm² using a resolution of 10 nm can typically take several hours, making inspection of a surface area of ​​hundreds of cm² (e.g., inspection of a conventional wafer) practically impossible. By using the system described herein, which uses 100 or more electron beams in parallel, it becomes possible to inspect the entire wafer surface (e.g., hundreds of cm²) on a reasonable time scale, for example, with scanning in several hours.

[0047] FIG. 2a is a schematic plan view of a multi-electron beam inspection system (100) according to embodiments described herein. The system (100) comprises a plurality of inspection columns (130) arranged in a two-dimensional array, the array extending in the X-direction and Y-direction over a movable stage (110), and a sample (10) placed on the movable stage (110) in the XY-plane. The sample is exemplarily exemplified as a round wafer.

[0048] FIG. 2b illustrates a plan view of the sample (10) of FIG. 2a without a plurality of columns (130) to illustrate a scanning pattern used according to the method described herein.

[0049] Multiple inspection columns (130), such as inspection columns (140), are schematically illustrated as circles in the plan view of FIG. 2a. The inspection columns can be configured according to the multiple inspection columns (130) of the system (100) of FIG. 1, and accordingly, the above descriptions, which are not repeated herein, may be referenced.

[0050] A two-dimensional array defined by a plurality of inspection columns (130) may be arranged into "lines" and "columns". At least some of the lines of the array may include five, ten, or more inspection columns, and at least some of the columns of the array may include five, ten, or more inspection columns. Specifically, the two-dimensional array may include a (sub-)array of A × B inspection columns arranged in lines and columns, where A and B are integers of five, ten, or more. A 10 × 10 (sub-)array of the two-dimensional array is illustrated in FIG. 2a by a dashed line (201).

[0051] In some embodiments, adjacent inspection columns among a plurality of inspection columns (130) are arranged at close distances to each other. In particular, the optical axes of two adjacent columns among the plurality of inspection columns (130) may be spaced apart from each other by distances of 5 cm or less, particularly 3 cm or less, more particularly about 2 cm. As schematically depicted in FIG. 2a, the distances (135) between two adjacent inspection columns in the rows of the array may be 5 cm or less, and / or the distances (135) between two adjacent inspection columns in the columns of the array may be 5 cm or less (distances (135) are measured between the optical axes of the inspection columns). Accordingly, an array of dense packing inspection columns is provided. In some embodiments, essentially, the entire sample support surface of the movable stage (110) may be covered by inspection columns, and each inspection column has a maximum dimension of 5 cm in a cross-sectional plane extending in the XY directions.

[0052] In some embodiments that can be combined with other embodiments described herein, the plurality of inspection columns (130) are small static electron beam micro-columns. The micro-columns may have a maximum dimension of 5 cm or less, particularly 3 cm or less, in a plane perpendicular to the optical axis. Providing a very large number of small micro-columns in a dense packing array enables a significant increase in the inspection speed of the sample.

[0053] During the inspection, multiple static electron beams form a two-dimensional beam array in cross-sectional planes parallel to the XY-plane. Likewise, multiple probe positions (106) are arranged in a two-dimensional array on the sample. Electron beams arranged adjacent to each other in a first direction (e.g., X-direction) and / or electron beams arranged adjacent to each other in a second direction (e.g., Y-direction) traversing the first direction may be spaced apart from each other by distances (135) of 5 cm or less, particularly 3 cm or less, more particularly about 2 cm.

[0054] Now, referring to FIG. 2b, each inspection column may be arranged over individual sub-regions of a sample (10) to inspect individual sub-regions with high resolution. The sample (10) may include a plurality of sub-regions (142) of essentially corresponding shapes (e.g., rectangular or quadratic sub-regions), and in each of the plurality of sub-regions (142), an electron beam associated with the plurality of sub-regions (142) may be focused at an individual probe position. Scanning may include moving a movable stage (110) in a predetermined scanning pattern so that the plurality of sub-regions (142) are simultaneously inspected by a plurality of electron beams until more than 90% of the surface area of ​​the plurality of sub-regions (142) is inspected, particularly with a resolution of 20 nm or less. In particular, by moving a movable stage to a predetermined scanning pattern, the essentially intact surface area of ​​multiple sub-regions can be inspected with high resolution (e.g., 20 nm or 10 nm or less) using static electron beams.

[0055] In some implementations, 10, 50, 100, or more sub-regions of a sample are inspected in parallel using multiple static electron beams with high resolution.

[0056] A plurality of sub-regions (141) may be essentially rectangular in shape and / or have individual surface areas of 3 cm² or more and 10 cm² or less, particularly about 4 cm². Specifically, the sub-regions may be rectangles having a width of 1.5 cm to 3 cm and a length of 1.5 cm to 3 cm, for example, rectangles having a width of about 2 cm and a length of about 2 cm, i.e., a surface area of ​​about 4 cm². Optionally, additional sub-regions including edge regions of the sample may have the shape of truncated rectangles. The rectangles may be inspected synchronously using static electron beams through stage movement.

[0057] Multiple sub-regions can be raster-scanned by moving a movable stage into a raster-scanning pattern. The line length of the raster-scanning pattern can essentially correspond to the width of the multiple sub-regions (141). Moving the movable stage into the raster-scanning pattern can essentially cause static electron beams to move over the sub-regions until the entire surface of the sub-regions is inspected with high resolution. In some embodiments, the scanning pattern may include alternating stage movements of scan lines in the X-direction and Y-shifts to individual next lines in the Y-direction. As schematically depicted for the enlarged sub-region (141) in FIG. 2b, to save time, inspection can be performed during both forward and back movements in the X-direction, that is, lines can be scanned alternately during the back and forward movements of the movable stage in the X-direction.

[0058] In some embodiments, more than 90% of the surface area of ​​the sample, particularly the essentially entire surface of the sample, is inspected using multiple electron beams with high resolution, particularly with a resolution of 10 nm or less. For example, the sample may be a wafer having a surface area of ​​400 cm² or more, and 360 cm² or more of the surface area, or the entire surface area, may be inspected with high resolution using static electron beams. Specifically, each of the 100 or more electron beams may inspect a sub-region of the sample having a surface area of ​​3 cm² or more to 10 cm² or less.

[0059] yes: Multiple inspection columns (130) may be configured to read secondary electron (SE) signals having a frequency of 100 MHz. A sub-region (141) of a sample to be inspected using one inspection column (140) may be a 2 cm × 2 cm rectangle. To obtain a resolution of 10 nm, 2e-6 secondary electron signals need to be read during stage movement along a 2 cm scan line, and a total of 2e-6 lines must be scanned. Considering an inspection frequency of 100 MHz, inspecting one scan line with a resolution of 10 nm takes 20 msec, and inspecting a total of 2e-6 lines takes about 11 hours. Accordingly, a sample having a surface area of ​​400 cm² can be inspected using a system as described herein, comprising 100 or more inspection columns with a resolution of 10 nm, in 11 hours or less compared to 11 × 100 hours (1.5 months) in a 1-beam system.

[0060] FIG. 3 illustrates a schematic cross-sectional view of an inspection column (140) of a multi-electron beam inspection system (100) according to embodiments described herein. A plurality of such inspection columns may be arranged adjacent to each other at close distances, as depicted in FIG. 1.

[0061] The inspection column (140) may be a static electron beam micro-column as previously described. The inspection column (140) may be configured to direct a static electron beam onto a sample (10). The inspection column (140) includes a beam emitter (131) for generating an electron beam that propagates along the optical axis (138) of the inspection column toward the sample (10). The inspection column (140) further includes a focusing lens (132) arranged within a microscope chamber (102) from which it can be discharged, and optionally a beam corrector (134), such as a stigmatizer. The focusing lens (132) is configured to focus the electron beam onto the sample (10) at a probe position (106).

[0062] Additionally, the inspection column (140) includes a detector (133) for detecting signal electrons (107). The signal from the detector (133) can be forwarded to an inspection controller (137) that receives the current stage position of the movable stage from the stage controller (180) with high accuracy, for example, in the range of 10 nm or less. By recording the electronic signal versus stage position during the movement of the movable stage to a predetermined scanning pattern, a high-resolution image of the sample can be generated and / or the sample can be inspected with high accuracy. Sample defects can be reliably detected.

[0063] The inspection column (140) may not include any scan deflector for scanning an electron beam across a sample for inspection purposes. Optionally, a beam deflector (not shown) for alignment or tuning purposes may be provided.

[0064] The electron beam can have a probe diameter of 20 nm or less at the probe position (106) so that inspection with sub-10 nm resolution is possible.

[0065] Accordingly, a relatively simple and small inspection row (140) suitable for high-resolution inspection of sample surfaces is provided. Accordingly, a very large number of inspection rows can be arranged close to each other in a two-dimensional array of inspection rows, which enables an increased inspection speed due to parallel inspection using many electron beams.

[0066] FIG. 4 illustrates a flowchart illustrating a method of inspecting a sample using a multi-electron beam inspection system according to the embodiments described herein.

[0067] In the box (510), the sample is placed on a movable stage such that the main surface of the sample essentially extends in the XY-plane. The sample may be any of a semiconductor wafer, a die package, or a coated substrate.

[0068] In the box (520), multiple electron beams are generated that propagate essentially parallel to each other toward the sample. The multiple electron beams are focused on the sample at multiple probe positions.

[0069] In the box (530), a sample is scanned by moving a movable stage in a predetermined scanning pattern while keeping multiple electron beams stationary. The movable stage can be moved, for example, in a raster-scanning pattern so that each of the multiple electron beams inspects a predetermined sub-region of the sample with high resolution. The scanning pattern of the movable stage causes synchronous movement of multiple electron beams for individual sub-regions in exactly the same way. Synchronous control of multiple scan deflectors is not required. This is because all electron beams are kept immobile, and relative movement is exclusively due to the movement of the stage. Signal capture accuracy can be improved, and the complexity of signal evaluation can be reduced. This allows the inspection speed to be further increased.

[0070] In the box (530), signal electrons emitted from the sample are detected by individual detectors of a plurality of inspection columns during the scanning movement of the movable stage. The detector signals can be transmitted to an inspection controller that records and / or evaluates the signal according to the current stage position. A high-resolution image of the sample can be generated and / or the sample can be inspected with high accuracy.

[0071] Scanning and detection in the box (530) may continue until a large portion of the sample, such as more than 50% of the sample surface, particularly more than 90% of the sample surface, or even an essentially intact sample surface, is inspected with high resolution. Optionally, by combining measurements from multiple inspection columns, an image of the intact sample may be generated.

[0072] The methods and systems described herein are beneficial and provide the following advantages: Inspection speed is increased due to parallel signal capture from a very large number of inspection columns. Samples can be inspected with high resolution, determined by the accuracy of the stage coordinates, i.e., limited by the interferometric resolution of the stage controller. Superior and stronger signals are acquired because the detector and inspection column designs are simpler and more efficient than those for scanning electron beam columns.

[0073] To summarize the above, the present disclosure specifically provides the following embodiments:

[0074] Example 1: A method for inspecting a sample using a multi-electron beam inspection system comprises: placing the sample on a movable stage extending in an XY plane; generating a plurality of electron beams that propagate essentially parallel to each other toward the sample; focusing the plurality of electron beams on the sample at a plurality of probe positions (106) arranged in a two-dimensional array; scanning the sample by moving the movable stage in a predetermined scanning pattern while maintaining the plurality of electron beams in a stationary state; and detecting signal electrons emitted from the sample during the movement of the movable stage to inspect the sample.

[0075] Example 2: In the method of Example 1, the plurality of electron beams includes 10 or more electron beams, in particular 50 or more electron beams, more particularly 100 or more electron beams.

[0076] Example 3: In the method of Example 1 or Example 2, a plurality of electron beams form a two-dimensional beam array in which electron beams arranged adjacently to each other in a first direction (X) and / or electron beams arranged adjacently to each other in a second direction (Y) transversing the first direction are each spaced apart from each other by distances of 5 cm or less, particularly 3 cm or less. In particular, the distances between adjacent electron beams are 1 cm to 3 cm, e.g., about 2 cm.

[0077] Example 4: In the method of any one of Examples 1 to 3, the sample is examined with a resolution of 20 nm or less, particularly 10 nm or less, and / or a plurality of electron beams have probe diameters of 40 nm or less, particularly 20 nm or less, more particularly 10 nm or less, or even 5 nm or less at a plurality of probe positions.

[0078] Example 5: In the method of any one of Examples 1 to 4, more than 90% of the surface area of ​​a sample is inspected using a plurality of electron beams, in particular, the entire sample surface is inspected using a plurality of electron beams. During the entire inspection in which the stage moves toward the plurality of electron beams in a predetermined scanning pattern, the plurality of electron beams may be kept stationary. Specifically, the electron beams are not scanned using a scan deflector. The inspection resolution may be 20 nm or less, in particular 10 nm or less.

[0079] Example 6: In the method of any one of Examples 1 to 5, the sample comprises a plurality of sub-regions having essentially the same shape, and in each of the plurality of sub-regions, an associated electron beam among a plurality of electron beams is focused at a probe position. The scanning step includes moving a movable stage in a predetermined scanning pattern so that the plurality of sub-regions are simultaneously scanned using a plurality of electron beams until more than 90% of the surface area of ​​the plurality of sub-regions is scanned, specifically until the essentially entire surface area of ​​the plurality of sub-regions is scanned.

[0080] Example 7: In the method of Example 6, a plurality of sub-regions are essentially rectangular in shape, and a movable stage is moved in a predetermined scanning pattern, such as a raster-scan pattern, until the essentially entire surface area of ​​the plurality of sub-regions is examined, particularly with a resolution of 20 nm or less. For example, the scanning pattern may include alternating stage movements of scan lines in the X-direction and Y-shifts in the Y-direction.

[0081] Example 8: In the method of Example 6 or Example 7, the sub-regions among the plurality of sub-regions have individual surface areas of 3 cm² or more and 10 cm² or less, particularly 4 cm² or more and 6 cm² or less. In particular, the sub-regions may be rectangles of about 2 cm × 2 cm.

[0082] Example 9: In the method of any one of Examples 1 to 8, the plurality of electron beams comprises 100 or more electron beams, the sample has a surface area of ​​400 cm² or more, and the movement of a movable stage to a predetermined scan pattern causes each of the plurality of electron beams to move over a surface area of ​​3 cm² or more to 10 cm² or less of a sub-region of the sample while providing a scan resolution of 20 nm or less.

[0083] Example 10: In the method of any one of Examples 1 to 9, the movable stage is interferometrically controlled, and the stage controller is configured to determine the stage position with a resolution of 20 nm or less, particularly 10 nm or less, or even 5 nm or less.

[0084] Example 11: In the method of any one of Examples 1 to 10, the sample is at least one of a die package comprising two or more connected dies and a wafer.

[0085] Example 12: In the method of any one of Examples 1 to 11, the sample is inspected at a working distance (WD) of 2 mm or more to 5 mm or less.

[0086] Example 13: A multi-electron beam inspection system for inspecting a sample in particular according to any of the above methods comprises a movable stage extending in an XY-plane for placing the sample on itself, and a plurality of inspection columns configured to generate a plurality of electron beams propagating essentially parallel to each other and to focus the plurality of electron beams onto the sample at a plurality of probe positions arranged in a two-dimensional array. Each of the plurality of inspection columns comprises a beam emitter, a focusing lens, and a detector for detecting signal electrons. The multi-electron beam inspection system further comprises a stage controller configured to move the movable stage in a predetermined scanning pattern during sample inspection while maintaining the plurality of electron beams in a stationary state.

[0087] Example 14: In the system of Example 13, the plurality of inspection columns do not include any scan deflectors. The focusing lens may be an electrostatic lens including, for example, an electrostatic octupole.

[0088] Example 15: In the system of Example 13 or Example 14, a plurality of inspection columns each further include a beam corrector, in particular a stigmator.

[0089] Example 16: In a system of any one of Examples 13 to 15, a plurality of inspection columns are configured to provide beam probes having probe diameters of 20 nm or less, particularly 10 nm or less, on a sample to obtain an inspection resolution of 10 nm or less.

[0090] Example 17: In a system of any one of Examples 13 to 16, a plurality of inspection columns are arranged in a closely packed array of A × B columns in the X-direction and Y-direction, and A and B are individual integers of 5 or more, particularly 10 or more.

[0091] Example 18: A multi-electron beam inspection system comprises a plurality of inspection columns arranged in a two-dimensional array in the X-direction and Y-direction and facing a movable stage for placing a sample on top of itself, and a stage controller configured to move the movable stage in the XY-plane in a predetermined scanning pattern. The plurality of inspection columns are static electron beam microcolumns without scan deflectors.

[0092] Example 19: In the system of Example 18, a plurality of inspection columns are configured for parallel sample inspection having a resolution of 20 nm or less, particularly 10 nm or less.

[0093] Example 20: In the system of Example 18 or Example 19, the two-dimensional array comprises an array of A × B columns in the X-direction and Y-direction, where A and B are individual integers of 5 or more, particularly 10 or more. The optical axes of two adjacent columns of the array may be spaced apart from each other by distances of 5 cm or less, particularly 3 cm or less.

[0094] Although the foregoing describes some embodiments, other and additional embodiments may be devised without departing from the basic scope, the scope of which is determined by the following claims.

Claims

Claim 1 A method for inspecting a sample (10), comprising: placing the sample on a movable stage (110) extending in an XY plane; generating a plurality of electron beams (105) propagating toward the sample (10); focusing the plurality of electron beams on the sample at a plurality of probe positions (106) arranged in a two-dimensional array; scanning the sample by moving the movable stage (110) in a predetermined raster-scanning pattern while maintaining the plurality of electron beams (105) in a stationary state; and detecting signal electrons (107) emitted from the sample during the scanning step to inspect the sample — the sample is inspected by moving the movable stage in the predetermined raster-scanning pattern with respect to the plurality of electron beams maintained in a stationary state — Claim 2 A method for inspecting a sample (10), wherein, in claim 1, the plurality of electron beams (105) comprises 10 or more electron beams. Claim 3 A method for inspecting a sample (10), wherein, in claim 1, the plurality of electron beams (105) form a two-dimensional beam array in which electron beams arranged adjacently to each other in a first direction (X) in cross-sectional planes parallel to the XY-plane are each spaced apart from each other by distances (135) of 5 cm or less. Claim 4 A method for inspecting a sample (10), wherein, in the first aspect, the plurality of electron beams (105) form a two-dimensional beam array in which electron beams arranged adjacently to each other in a first direction (X) and electron beams arranged adjacently to each other in a second direction (Y) transversing the first direction are each spaced apart from each other by distances (135) of 5 cm or less. Claim 5 A method for inspecting a sample (10), wherein, in any one of claims 1 to 4, the sample (10) is inspected with a resolution of 20 nm or less. Claim 6 In claim 5, the method of inspecting the sample (10) is such that the sample (10) is inspected with a resolution of 10 nm or less. Claim 7 A method for inspecting a sample (10) in which at least 90% of the surface area of ​​the sample is inspected using the plurality of electron beams (105) in any one of claims 1 to 3. Claim 8 A method for inspecting a sample (10), wherein, in any one of claims 1 to 4, the sample (10) comprises a plurality of sub-regions (142) of the same shape, and in each of the plurality of sub-regions (142), an associated electron beam among the plurality of electron beams is focused at a probe position, and the scanning step comprises moving the movable stage (110) to the predetermined scanning pattern so that the plurality of sub-regions (142) are simultaneously inspected by the plurality of electron beams until more than 90% of the surface area of ​​the plurality of sub-regions (142) is inspected. Claim 9 A method for inspecting a sample (10), wherein the sub-regions are rectangular in shape, in claim 8. Claim 10 A method for inspecting a sample (10), wherein, in claim 8, the sub-regions each have an individual surface area of ​​3 cm² or more to 10 cm² or less. Claim 11 A method for inspecting a sample (10), wherein, in any one of claims 1 to 4, the plurality of electron beams comprises 100 or more electron beams, the sample has a surface area of ​​400 cm² or more, and the plurality of electron beams have a surface area of ​​3 cm² or more to 10 cm² or less with a resolution of 20 nm or less. Claim 12 A method for inspecting a sample (10), wherein, in any one of claims 1 to 4, the movable stage (110) is interferometer-controlled and the stage controller (180) is configured to determine the stage position with an accuracy of 10 nm or less. Claim 13 A method for inspecting a sample (10) in any one of claims 1 to 4, wherein the sample is inspected without beam scanning using a scan deflector by moving the movable stage to the predetermined scanning pattern with respect to the plurality of electron beams maintained in a stationary state. Claim 14 A multi-electron beam inspection system (100) for inspecting a sample (10), comprising: a movable stage (110) extending in an XY plane for placing the sample on itself; a plurality of inspection columns (130) configured to generate a plurality of electron beams (105) and to focus the plurality of electron beams onto the sample at a plurality of probe positions (106) arranged in a two-dimensional array—each of the plurality of inspection columns (130) comprises: a beam emitter (131); a focusing lens (132); and a detector (133) for detecting signal electrons (107); A multi-electron beam inspection system (100) for inspecting a sample (10), comprising: a stage controller (180) configured to move the movable stage (110) in a predetermined raster-scanning pattern during inspection of the sample while maintaining the plurality of electron beams (105) in a stationary state — the plurality of inspection columns (130) do not include scan deflectors — Claim 15 In claim 14, the plurality of inspection columns (130) further comprise a beam corrector (134), a multi-electron beam inspection system (100) for inspecting a sample (10). Claim 16 A multi-electron beam inspection system (100) for inspecting a sample (10), wherein, in claim 14 or 15, the plurality of inspection columns (130) are configured to provide beam probes having probe diameters of 20 nm or less on the sample. Claim 17 A multi-electron beam inspection system (100) for inspecting a sample (10), wherein the plurality of inspection columns (130) comprises an array of A × B inspection columns extending in the X-direction and Y-direction, and A and B are integers greater than or equal to 5. Claim 18 delete Claim 19 delete Claim 20 A multi-electron beam inspection system (100) for inspecting a sample (10), wherein, in claim 14 or 15, the two-dimensional array comprises an array of A × B inspection columns, where A and B are integers greater than or equal to 5, and the optical axes of two adjacent columns of the array are each spaced apart from each other by distances (135) of less than or equal to 3 cm.

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