High-sensitivity optical measurement in scanning mode and stationary mode

Abstract

The metrology system 100 may include a metrology tool for selectively performing metrology measurements in a stationary mode, in which one or more metrology targets on the sample do not move during the measurement, or in a scanning mode, in which one or more metrology targets move during the measurement, and a controller 130 communicatively coupled to the translation stage 118 and at least one of the one or more detectors 104. The controller 130 may receive locations of the metrology targets on the sample 102 to be investigated, designate the metrology targets for investigation in the stationary mode or the scanning mode, and based on the designation, direct the metrology tool to perform metrology measurements on the metrology targets in the stationary mode or the scanning mode, and generate metrology data for the sample based on the metrology measurements on the multiple metrology targets.

Description

Technical Field

[0001] The present disclosure generally relates to optical measurement, and more particularly to optical measurement in scanning mode and stationary mode.

Background Art

[0002] Measurement systems typically generate measurement data associated with a sample by measuring or otherwise investigating dedicated measurement targets dispersed across the sample. Further, different measurement tools can be designed to investigate the measurement targets using different techniques. For example, some measurement tools can be designed to investigate the measurement target while the target is stationary within the field of view. For this reason, such tools can use a move-and-measure (MAM) operation mode in which the sample is translated to position the measurement target of interest within the measurement field of view and measurements are taken while the sample is stationary, and then the sample is translated to position an additional measurement target of interest within the measurement field of view. As another example, some measurement tools can be designed to investigate the measurement target while the sample is moving (e.g., scanning operation mode).

[0003] As a result of the increasing demand for smaller semiconductor devices, there is an increasing need for accurate and efficient measurement accordingly. However, measurement tools with dedicated MAM mode or scanning mode can be inefficient for investigating measurement targets dispersed across the sample.

[0004] Furthermore, regardless of the operation mode, the measurement tool can use one or more optical configurations (e.g., illumination spectrum, polarization, etc.) to investigate a particular measurement target and generate measurement data based on the combined investigation to achieve the desired measurement sensitivity. However, variations in the measurement conditions between investigations using different optical configurations can limit the achievable measurement sensitivity.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, it is desirable to provide a system and method for correcting the above drawbacks.

Means for Solving the Problems

[0007] A measurement system according to one or more exemplary embodiments of the present disclosure is disclosed. In one exemplary embodiment, the system is configured to selectively perform measurement measurements in a stationary mode in which one or more measurement targets on the sample do not move during measurement, or in a scanning mode in which one or more measurement targets move during measurement. In another exemplary embodiment, the system includes a translation stage and a controller communicatively coupled to at least one of one or more detectors. In another exemplary embodiment, the controller receives the location of measurement targets on the sample to be investigated. In another exemplary embodiment, the controller designates measurement targets for investigation in the stationary mode or the scanning mode. In another exemplary embodiment, the controller instructs the measurement tool to perform measurement measurements on the measurement targets in the stationary mode or the scanning mode based on the designation. In another exemplary embodiment, the controller generates measurement data of the sample based on measurement measurements for a plurality of measurement targets.

[0008] A measurement method according to one or more exemplary embodiments of the present disclosure is disclosed. In one exemplary embodiment, the method includes receiving the location of measurement targets on a sample to be investigated. In another exemplary embodiment, the method includes specifying measurement targets for investigation in a stationary mode where one or more measurement targets on the sample do not move during measurement, or in a scanning mode where one or more measurement targets move during measurement. In another exemplary embodiment, the method includes instructing a measurement tool to perform measurement on the measurement targets in the stationary mode or the scanning mode based on the specification via one or more drive signals. In another exemplary embodiment, the method includes generating measurement data of the sample based on the measurement on the measurement targets.

[0009] A measurement system according to one or more exemplary embodiments of the present disclosure is disclosed. In one exemplary embodiment, the system comprises a multi-channel imaging subsystem. In another exemplary embodiment, the multi-channel imaging subsystem comprises an illumination source. In another exemplary embodiment, the multi-channel imaging subsystem comprises one or more illumination optics for directing illumination from the illumination source towards the sample. In another exemplary embodiment, the multi-channel imaging subsystem comprises one or more light collecting optics for collecting light emitted from the sample in response to illumination from the illumination source. In another exemplary embodiment, the multi-channel imaging subsystem comprises a detector that generates two or more images of the sample at an exposure window. In another exemplary embodiment, the system comprises a controller communicatively coupled to the detector. In another exemplary embodiment, the controller generates one or more drive signals for at least one of the illumination source, one or more illumination optics, one or more light collecting optics, or the detector to sequentially provide N optical configurations of the multi-channel imaging subsystem within the exposure window of the detector, where N is a selected integer greater than 1. In another exemplary embodiment, the detector generates N images of the sample during a readout phase of the detector associated with the exposure window, where a particular one of the N images corresponds to a particular one of the N optical configurations. In another exemplary embodiment, the controller generates measurement data associated with the sample based on the N images of the sample.

[0010] It will be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention.

[0011] Many advantages of the present disclosure can be better understood by those skilled in the art by referring to the accompanying drawings.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

DETAILED DESCRIPTION OF THE INVENTION

[0013] Reference is now made in detail to the subject matter of the disclosed invention, which is illustrated in the accompanying drawings. The present disclosure is particularly shown and described with respect to several embodiments and specific features thereof. The embodiments described herein are to be construed as illustrative and not restrictive. It should be readily understood by those skilled in the art that various modifications and changes in form and detail can be made without departing from the spirit and scope of the present disclosure.

[0014] Embodiments of the present disclosure are directed to systems and methods for high-throughput and high-sensitivity optical measurement.

[0015] Some embodiments of the present disclosure are directed to optical measurements using dynamically selectable operating modes. For example, a measurement system can be configured to support both a stationary (e.g., MAM) operating mode for measuring a measurement target while the sample is stationary and a scanning operating mode for measuring the measurement target while the sample is in motion.

[0016] The stationary mode can consist of translating the sample until the measurement target is positioned within the measurement field of view, waiting for the position of the sample to stabilize, performing the measurement (e.g., generating an image, etc.), translating the sample to position a new measurement target within the measurement field of view, and repeating the process. In contrast, the scanning mode can consist of translating the sample to a desired starting location, scanning the sample along a controlled path that includes one or more measurement targets during the measurement, reaching the desired ending location, translating the sample to a new starting location, and repeating the process.

[0017] It is recognized herein that the efficiency of an investigation using the stationary and scanning modes may depend on the particular layout and type of measurement targets in the sample. For example, the scanning operating mode may be suitable, but not limited to, when multiple measurement targets are arranged at narrow intervals along a line. Such a configuration is common, for example, at locations within a die of a semiconductor sample (e.g., die streets). In this regard, the continuous scanning provided by the scanning mode can efficiently investigate multiple targets. As another example, the stationary mode may be suitable, but not limited to, when the measurement targets are sparsely distributed across a wafer and / or not distributed in a regular pattern suitable for line scanning.

[0018] Additional embodiments of the present disclosure are directed to specifying or otherwise selecting which mode of operation to use for particular measurement targets distributed across a sample. It is recognized herein that the distribution of measurement targets across a single sample can include some areas suitable for stationary mode investigations and other areas suitable for scanning mode investigations. Thus, specifying particular measurement targets for stationary mode investigations and others for scanning mode investigations can facilitate high throughput investigation of the sample as a whole.

[0019] In some embodiments, the measurement system receives the locations of a plurality of measurement targets distributed across a sample and designates each of the measurement targets for investigation using a selected mode (e.g., stationary or scanning). The measurement system can use a variety of criteria to determine which mode to use for a particular target. For example, the measurement system can make the designation based on target type, location of the target, proximity to one or more additional measurement targets of the plurality of measurement targets, or target density. Additionally, the measurement system can make the designation based on a weighting function in which a plurality of criteria are given relative weights.

[0020] Some embodiments of the present disclosure are directed to generating multiple measurements of measurement targets quickly using multiple optical configurations within a single exposure window of a detector. It is recognized herein that an optical measurement system can typically generate one or more images of a sample that can be analyzed to determine measurement measurements of interest (e.g., overlay measurement measurements, critical dimension (CD) measurements, sidewall angle (SWA) measurements, defect identification, etc.). In this regard, the measurement system can typically include a detector located in the field plane (e.g., the plane bonded to the sample to generate an image of one or more features on the sample), the pupil plane (e.g., generating a pupil image associated with the angle at which light is emitted from the sample), or both.

[0021] Furthermore, it may be advantageous to generate multiple images of a particular optical target having different optical configurations. For the purposes of the present disclosure, an optical configuration can include a particular set of illumination, light collection, or imaging parameters used to generate an image. For example, the optical configuration can include, but is not limited to, the spectrum of the illumination beam, the spectrum of the light collected from the sample used to generate the image, the polarization of the illumination beam, the polarization of the light collected from the sample used to generate the image, the location of the image plane relative to the surface of the sample, the aperture diameter of one or more diaphragms or pupils (e.g., field stop, aperture stop, etc.), the location of one or more diaphragms or pupils (e.g., can be used to adjust telecentricity), or detector settings (e.g., gain, exposure time, etc.).

[0022] The image quality associated with a particular measurement target can depend on the interaction between the imaging system and the characteristics of the particular measurement target. For example, the absorption, reflection, refraction, and / or scattering of light from the measurement target can vary based on the composition, size, and layout of features in the measurement target, as well as the wavelength and polarization of the illumination beam.

[0023] The multiple images of the target generated using different optical configurations can be utilized in various ways to achieve a desired performance level (e.g., desired sensitivity, signal-to-noise ratio (SNR), desired image contrast, etc.). For example, generating multiple images of the target using different optical configurations can facilitate the selection of a particular optical configuration for each measurement that produces an image having image quality within a selected specification (e.g., in a processing step). As another example, an algorithm for generating a measurement can incorporate multiple sample images generated using a known set of different optical configurations.

[0024] It is further recognized that it is often desirable to generate images having different optical configurations under the same conditions. However, measurement systems typically include error sources that vary over time, resulting in variations in the optical configuration over time. For example, the spectrum or beam profile of an illumination beam may exhibit temporal jitter or drift. As another example, a translation stage that holds a sample may similarly exhibit temporal jitter or drift. Such temporal error sources can be particularly problematic for systems that utilize multiple images generated with different optical configurations, where differences between the images due to system-level variations may appear as measurement errors related to the sample.

[0025] Accordingly, some embodiments of the present disclosure are directed to forming images having multiple configurations within a common exposure window. For example, a measurement system can rapidly switch between different optical configurations.

[0026] For example, a conventional measurement system can generate an image by exposing a sample to a given optical configuration and, in response, exposing detector pixels in an exposure window. At this time, the conventional measurement system can read out the stored charge to form an image associated with the given optical configuration.

[0027] In embodiments of the present disclosure, a measurement system can generate multiple images of a sample using different optical configurations in a single exposure window by rapidly changing the optical configuration in the exposure window and generating multiple images associated with different optical configurations during a common readout phase. In this regard, the duration between multiple images of the sample associated with different optical configurations can be made substantially minimal. Accordingly, error sources that vary over time can affect each of the different images substantially similarly.

[0028] In some embodiments, the measurement system includes a scanning sensor, such as, but not limited to, a line sensor or a time delay integration (TDI) sensor, to generate a continuous output image (e.g., a strip image) as the sample is translated through the measurement field. Thus, a measurement system configured in accordance with the present disclosure can synchronize the translation speed of the sample and the clock rate of the scanning sensor such that different optical configurations are sequentially cycled through and each pixel row corresponds to a different optical configuration. In this regard, the output image can be composed of interleaved images, each associated with a different optical configuration. Next, the output image can be divided into a plurality of separate images in a post-processing step.

[0029] In some embodiments, the measurement system includes a stationary multi-tap imaging sensor. In this regard, each pixel can include two or more taps, where the charge stored in the pixel can be directed to any of the taps through a drive signal. A measurement system configured in accordance with the present disclosure can sequentially cycle through a plurality of different optical configurations and synchronize the drive signals of the pixels to direct the charge associated with the plurality of different optical configurations to dedicated taps in an exposure window. Next, a plurality of images from the plurality of taps can be generated during a subsequent readout phase.

[0030] Referring now to FIGS. 1-5B, a system and method for efficient and sensitive measurement are described in more detail.

[0031] FIG. 1 is a block diagram of a measurement system 100 according to one or more embodiments of the present disclosure. The measurement system 100 can generate one or more images of a sample 102 in at least one detector 104 using any method known in the art. In one embodiment, the detector 104 is positioned on the field plane to generate an image of one or more features of the sample 102. In another embodiment, the detector 104 is positioned on the pupil plane to generate an image based on the angle of light emitted from the sample 102 (e.g., based on reflection, refraction, scattering, etc.). In this regard, the measurement system 100 can operate as a scatterometry-based measurement tool.

[0032] In one embodiment, the measurement system 100 includes an illumination source 106 for generating an illumination beam 108. The illumination beam 108 can include one or more selected wavelengths of light including, but not limited to, vacuum ultraviolet radiation (VUV), deep ultraviolet radiation (DUV), ultraviolet (UV) radiation, visible radiation, infrared (IR) radiation. The illumination source 106 can further generate an illumination beam 108 including any range of selected wavelengths. In another embodiment, the illumination source 106 can include a spectrally tunable illumination source for generating an illumination beam 108 having a tunable spectrum.

[0033] The illumination source 106 can further generate an illumination beam 108 having any temporal profile. For example, the illumination source 106 can generate a continuous illumination beam 108, a pulsed illumination beam 108, or a modulated illumination beam 108. Further, the illumination beam 108 can be delivered from the illumination source 106 via free-space propagation or guided light (e.g., an optical fiber, an optical pipe, etc.).

[0034] In another embodiment, the illumination source 106 directs the illumination beam 108 towards the sample 102 via the illumination path 110. The illumination path 110 can include one or more lenses 112 or additional illumination optical components 114 suitable for modifying and / or adjusting the illumination beam 108. For example, the one or more illumination optical components 114 can include, but are not limited to, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, one or more beam shapers, or one or more shutters (e.g., mechanical shutter, electro-optical shutter, acousto-optical shutter, etc.). As another example, the one or more illumination optical components 114 can include an aperture stop for controlling the angle of illumination with respect to the sample 102 and / or a field stop for controlling the spatial extent of illumination on the sample 102. In one example, the illumination path 110 includes an aperture stop located on a surface joined to the rear focal plane of the objective lens 116 to provide telecentric illumination of the sample. In another embodiment, the measurement system 100 includes an objective lens 116 for focusing the illumination beam 108 onto the sample 102.

[0035] In another embodiment, the sample 102 is disposed on a sample stage 118. The sample stage 118 can include any device suitable for positioning the sample 102 within the measurement system 100. For example, the sample stage 118 can include any combination of a linear translation stage, a rotational stage, a chip / tilt stage, etc.

[0036] In another embodiment, the detector 104 is configured to capture radiation (e.g., sample light 120) emitted from the sample 102 through the light collection path 122. For example, the light collection path 122 may include a condenser lens (e.g., the objective lens 116 as shown in FIG. 1) or one or more additional light collection path lenses 124, but this is not essential. In this regard, the detector 104 may receive radiation reflected or scattered from the sample 102 (e.g., via specular reflection, diffuse reflection, etc.) or generated by the sample 102 (e.g., luminescence associated with the absorption of the illumination beam 108).

[0037] The light collection path 122 may further include any number of light collection optical components 126 for directing and / or modifying the illumination collected by the objective lens 116, including but not limited to one or more light collection path lenses 124, one or more filters, one or more polarizers, or one or more beam blocks. Further, the light collection path 122 may include a field stop for controlling the spatial extent of the sample imaged on the detector 104, or an aperture stop for controlling the angular extent of the illumination from the sample used to generate an image on the detector 104. In another embodiment, the light collection path 122 includes an aperture stop located on a surface joined to the rear focal plane of the optical elements of the objective lens 116 to provide telecentric imaging of the sample.

[0038] Detector 104 can include any type of optical detector known in the art suitable for measuring the illumination received from sample 102. For example, detector 104 can include, but is not limited to, a charge-coupled device (CCD), a complementary metal-oxide semiconductor (CMOS) sensor, a photomultiplier tube (PMT) array, or an avalanche photodiode (APD) array, etc., a sensor suitable for generating one or more images of stationary sample 102 (e.g., in a stationary operation mode). Further, detector 104 can include a multi-tap sensor having two or more taps per pixel, including, but not limited to, a multi-tap CMOS sensor. In this regard, the charge in a multi-tap pixel can be directed to any selected tap in the exposure window based on one or more drive signals to the pixel. Thus, a multi-tap sensor including an array of multi-tap pixels can generate a plurality of images, each associated with a different tap of the associated pixels, during a single readout phase. Further, for the purposes of the present disclosure, the taps of a multi-tap sensor can refer to output taps connected to the associated pixels. In this regard, separate images can be generated by reading out each tap of the multi-tap sensor (e.g., in a readout phase).

[0039] As another example, detector 104 can include a sensor suitable for generating one or more images of a moving (e.g., scanning operation mode) sample 102. For example, detector 104 can include a line sensor including rows of pixels. In this regard, measurement system 100 can translate sample 102 in a scanning direction perpendicular to the rows of pixels through the measurement field of view and continuously clock the line sensor in a continuous exposure window to generate a continuous image (e.g., a strip image) one row at a time.

[0040] In another example, detector 104 can comprise a TDI sensor that includes a plurality of pixel rows and readout rows. The TDI sensor can operate similarly to a line sensor, except that a clocking signal can continuously move charge from one pixel row to the next until the charge reaches the readout row where the image row is generated. By synchronizing the charge transfer to the movement of the sample along the scan direction (e.g., based on the clocking signal), the charge can continue to increase across the pixel rows to provide a higher signal-to-noise ratio compared to a line sensor.

[0041] In another embodiment, detector 104 can comprise a spectroscopic detector suitable for identifying the wavelength of the radiation emitted from sample 102. In another embodiment, measurement system 100 can comprise a plurality of detectors (e.g., associated with a plurality of beam paths generated by one or more beam splitters to facilitate a plurality of measurement measurements by measurement system 100). For example, measurement system 100 can comprise one or more detectors suitable for stationary mode imaging and one or more detectors 104 suitable for scanning mode imaging. In another embodiment, measurement system 100 can comprise one or more detectors 104 suitable for both stationary imaging mode and scanning imaging mode. For example, the TDI sensor can operate in stationary mode by not clocking the TDI sensor to transfer charge between pixel rows in the exposure window. Next, when the exposure window is stopped (e.g., by switching off illumination source 106 by a shutter, etc.) and no additional light is incident on the pixels, the TDI sensor can be clocked to transfer charge row by row to the readout row to generate an image having a length equal to the number of pixel rows.

[0042] In one embodiment shown in FIG. 1, the measurement system 100 includes a beam splitter 128 oriented such that the objective lens 116 can simultaneously direct the illumination beam 108 toward the sample 102 and collect the radiation emitted from the sample 102. In this regard, the measurement system 100 can be configured in an epi-illumination mode.

[0043] In another embodiment, the incident angle of the illumination beam 108 with respect to the sample 102 is adjustable. For example, the path of the illumination beam 108 through the beam splitter 128 and the objective lens 116 can be adjusted to control the incident angle of the illumination beam 108 with respect to the sample 102. In this regard, the illumination beam 108 can have a nominal path through the beam splitter 128 and the objective lens 116 such that the illumination beam 108 has a normal incident angle with respect to the sample 102. As another example, the incident angle of the illumination beam 108 with respect to the sample 102 can be controlled by changing the position and / or angle of the illumination beam 108 with respect to the beam splitter 128 (e.g., by a rotatable mirror, a spatial light modulator, a free-form illumination source, etc.). In another embodiment, the illumination source 106 directs one or more illumination beams 108 toward the sample 102 at an angle (e.g., an angle of incidence, an angle of 45 degrees, etc.).

[0044] In another embodiment, the measurement system 100 includes a controller 130. In another embodiment, the controller 130 includes one or more processors 132 configured to execute program instructions maintained on a memory medium 134. In this regard, one or more processors 132 of the controller 130 can execute any of the various process steps described throughout the present disclosure. Further, the controller 130 can be configured to receive data including, but not limited to, measurement data (e.g., alignment measurement results, images of the sample, pupil images, etc.) or measurement criteria (e.g., accuracy, device factor errors, sensitivity, diffraction efficiency, etc.).

[0045] One or more processors 132 of the controller 130 can include any processing element known in the art. In this sense, one or more processors 132 can include any microprocessor-type device configured to execute algorithms and / or instructions. In one embodiment, one or more processors 132 can consist of any other computer system (e.g., a network computer) configured to execute a program configured to operate a desktop controller, a mainframe computer system, a workstation, an image computer, a parallel processor, or the measurement system 100 as described throughout the present disclosure. It is further recognized that the term "processor" can be broadly defined to include any device having one or more processing elements that execute program instructions from a non-transitory memory medium 134. Further, the steps described throughout the present disclosure can be executed by a single controller 130 or alternatively by a plurality of controllers. Further, the controller 130 can include one or more controllers housed in a common housing or in a plurality of housings. In this way, any controller, or combination of a plurality of controllers, can be individually packaged as a module suitable for incorporation into the measurement system 100. Further, the controller 130 can analyze the data received from the detector 104 and send this data to additional components within the measurement system 100 or outside the measurement system 100.

[0046] The memory medium 134 may include any storage medium known in the art suitable for storing program instructions executable by one or more associated processors 132. For example, the memory medium 134 may include a non-transitory memory medium. As another example, the memory medium 134 may include, but is not limited to, read-only memory, random access memory, magnetic or optical memory devices (e.g., disks), magnetic tapes, solid state drives, and the like. It should be further noted that the memory medium 134 may be housed within a common controller housing having one or more processors 132. In one embodiment, the memory medium 134 may be located remotely with respect to the physical location of one or more processors 132 and the controller 130. For example, one or more processors 132 of the controller 130 may access a remote memory (e.g., a server) accessible through a network (e.g., the Internet, an intranet, etc.). Accordingly, the above description should be construed as illustrative and not as limiting of the present invention.

[0047] In another embodiment, the controller 130 is communicatively coupled to one or more elements of the measurement system 100. In this regard, the controller 130 can transmit and / or receive data from any component of the measurement system 100. Further, the controller 130 can direct or otherwise control any component of the measurement system 100 by generating one or more drive signals for the associated components. For example, the controller 130 may be communicatively coupled to the detector 104 to receive one or more images from the detector 104. Further, the controller 130 can provide one or more drive signals for the detector 104 to perform any of the detection techniques described herein, such as, but not limited to, a clocking signal for controlling an exposure and / or readout window, a clocking signal for transferring charge between pixel rows of a TDI sensor, a drive signal to a multi-tap sensor for directing charge to a particular tap, etc. As another example, the controller 130 can be communicatively coupled to any combination of components that control the optical configuration associated with an image, including, but not limited to, the illumination source 106, the illumination optical component 114, the light collection optical component 126, the detector 104, etc.

[0048] Referring now to FIG. 2, a flow diagram is disclosed showing steps for performing a method 200 for efficient measurement according to one or more embodiments of the present disclosure. In particular, the method 200 can be used to dynamically switch between a scanning measurement mode and a stationary (e.g., MAM) measurement mode to efficiently survey measurement targets dispersed across the sample 102. The Applicant notes that the embodiments and realizable techniques already described herein in the context of the measurement system 100 should be construed as being extended to the method 200 as well. However, it is further noted that the method 200 is not limited to the architecture of the measurement system 100.

[0049] In one embodiment, method 200 includes step 202 of receiving the locations of measurement targets in sample 102 to be investigated. For example, the measurement targets can be dispersed at various locations across sample 102.

[0050] FIG. 3 is a conceptual top view of measurement targets 302 dispersed across sample 102 according to one or more embodiments of the present disclosure. Sample 102 can include measurement targets 302 at various locations across a surface including, but not limited to, the surface in one or more dies 304 (e.g., in one or more die streets 306) or adjacent to or between adjacent dies 304. Further, a given die 304 or die street 306 can include any number of measurement targets 302.

[0051] It is recognized herein that in order to provide representative characteristics of the entire surface of sample 102, typically many measurement targets 302 are investigated across the sample. Further, various sampling schemes can be utilized to efficiently select which of any available measurement targets 302 are investigated in a particular sample 102 at a particular point in time. Thus, the set of locations of measurement targets in sample 102 received in step 202 need not include all available measurement targets 302 in a particular sample 102.

[0052] In another embodiment, method 200 includes step 204 of designating measurement targets for investigation in a stationary mode or a scanning mode. In this regard, each (or at least some) of the measurement targets 302 to be investigated in sample 102 can be designated or otherwise allocated for investigation using either a stationary mode or a scanning mode. In another embodiment, step 204 includes separating at least some of the designated measurement targets 302 for investigation in a scanning mode into one or more scanning groups. For example, a scanning group can include two or more measurement targets 302 that are investigated in a common scan of measurement system 100.

[0053] The measurement mode for each specific measurement target 302 can be determined based on any selected criterion or combination of criteria.

[0054] In one embodiment, the measurement mode and / or the scanning group are selected based on the target type. Typically, the sample 102 can include multiple types of measurement targets 302. For example, the sample 102 can include, but is not limited to, overlay measurement targets 302, critical dimension measurement targets 302, or SWA measurement targets 302, where each type of measurement target 302 has a different arrangement of features (e.g., different target designs) in one or more layers of the sample 102. In another example, the sample 102 can include multiple measurement targets 302 that are configured to generate similar measurement data (e.g., overlay, CD, SWA, etc.) but have different designs. Thus, the same target design may be more suitable for a particular measurement mode (e.g., stationary mode or scanning mode). In this regard, step 204 can include designing the measurement mode for a specific measurement target 302 based on the target type.

[0055] In another embodiment, the measurement mode and / or the scanning group are selected based on the target density and / or proximity of neighboring measurement targets 302. For example, it may be more efficient to investigate multiple adjacent measurement targets 302 in one or more scans (e.g., swaths) in the scanning mode in order to avoid the long acceleration, deceleration, and stabilization times associated with stationary measurements. As another example, it may be more efficient to use the stationary mode to investigate irregularly and / or sparsely distributed measurement targets 302. In particular, when multiple measurement targets 302 cannot be investigated using a common scan of a reasonable length, the time associated with performing separate scans for individual targets may not be as efficient as stationary measurements.

[0056] In another embodiment, the measurement mode and / or the scanning group are selected based on the location of the target. A particular area of the sample 102 may be better suited for measurement using a particular measurement mode. For example, a plurality of measurement targets 302 aligned along a narrow dice street 306 can be efficiently measured in one or more scans in the scanning mode. As another example, measurement targets 302 diffused within one or more dies 304 can be efficiently measured in the stationary mode.

[0057] The step 204 of specifying the measurement target for investigation in the stationary mode or the scanning mode can be executed locally or remotely in a particular measurement tool. For example, if step 204 is executed remotely, the location of the measurement target 302 (e.g., associated with step 202) and the associated specified measurement mode (e.g., associated with step 204) can be located within a sampling recipe (e.g., a sampling plan) received by the measurement tool.

[0058] In another embodiment, the method 200 includes a step 206 of performing measurement measurements on a plurality of measurement targets in the stationary mode or the scanning mode based on the specification.

[0059] The measurement tool can include any type of measurement tool known in the art suitable for performing both stationary mode measurements and scanning mode measurements.

[0060] In one embodiment, the measurement tool includes a TDI sensor (e.g., detector 104). In this regard, the measurement tool can perform scanning mode measurements by exposing the sample 102 to illumination from an illumination source (e.g., illumination source 106) in the exposure window, synchronizing the TDI sensor with the movement of the sample in the exposure window, and generating an image for each row during the movement of the sample 102.

[0061] In another embodiment, the measurement tool exposes the sample to illumination from an illumination source in the exposure window while the sample is stationary, without clocking the TDI sensor to transfer charge, and clocks the TDI sensor to transfer charge row by row to generate an image when the sample is not exposed to illumination from the illumination source, thereby performing stationary mode measurement.

[0062] In another embodiment, the measurement tool can perform static mode measurement by exposing the sample to illumination from an illumination source in the exposure window while the sample is stationary and reading out an image of the sample using an imaging detector after the exposure window.

[0063] In another embodiment, method 200 includes step 208 of generating measurement data of a sample based on measurement measurements for a plurality of measurement targets. For example, step 208 can include generating any type of measurement data based on the measured measurement target 302, including but not limited to overlay measurement data, CD measurement data, or SWA measurement data.

[0064] Referring now to FIGS. 4-5B, a system and method for high-sensitivity measurement measurements according to one or more embodiments of the present disclosure will be described in more detail.

[0065] As described above herein, in some embodiments, measurement system 100 generates a plurality of images of a sample having different optical configurations at a single exposure window of detector 104. The images can include any combination of field-of-view images and pupil-plane images. Further, the plurality of images can be generated in a stationary mode and / or a scanning mode. In this regard, measurement system 100 can provide dynamic selection of both stationary mode measurements (such as shown in FIG. 2, for example) or scanning mode measurements, and a plurality of images of a sample having different optical configurations at a single exposure window in either the stationary mode or the scanning mode. However, it is recognized herein that measurement system 100 can be configured exclusively for stationary and / or scanning mode operation within the spirit and scope of the present disclosure.

[0066] Measurement system 100 can generate alternative optical configurations for imaging sample 102 using any technique known in the art.

[0067] In one embodiment, measurement system 100 can adjust one or more components in illumination path 110 to generate a plurality of optical configurations.

[0068] For example, illumination source 106 can be configured as a multi-channel illumination source to sequentially generate illumination having two or more optical configurations. In some embodiments, controller 130 can be communicatively coupled to any combination of components in measurement system 100 and can control the components (e.g., via drive signals) to provide a plurality of optical configurations.

[0069] FIG. 4 is a conceptual diagram of a multi-channel illumination source 106 configured to sequentially generate illumination having two or more optical configurations along a common optical column, according to one or more embodiments of the present disclosure.

[0070] In one embodiment, the illumination source 106 includes a broadband light source 402, two or more channels 404 having different optical paths, and a beam combiner 406 for combining the light from the channels 404 into a common optical column 408. Further, any channel 404 can include separate components for providing a separately tunable optical profile. For example, any channel 404 can include a spectral filter 410 that passes a selected portion of the spectrum of light from the broadband light source 402, a shutter 412, one or more neutral density filters, one or more apertures (e.g., functioning as a field stop or an aperture stop), or one or more polarizers.

[0071] In another embodiment, although not shown, the multi-channel illumination source 106 can include one or more tunable optical elements (e.g., a tunable spectral filter, a shutter, an aperture, a polarizer, etc.) along a single common optical column 408.

[0072] In another embodiment, the measurement system 100 can adjust one or more components of the condenser path 122 to generate a plurality of optical configurations. For example, the measurement system 100 can adjust one or more spectral filters, one or more shutters, one or more neutral density filters, one or more apertures, or one or more polarizers in the condenser path 122 (e.g., via the controller 130) to generate a plurality of optical configurations. As another example, the measurement system 100 can adjust one or more parameters of the detector 104, such as, but not limited to, gain or exposure window (e.g., integration time), to generate a plurality of optical configurations.

[0073] The measurement system 100 can include any type of detector 104 suitable for generating a plurality of images associated with different optical configurations within a single exposure window of the detector 104. The plurality of images can be interleaved into a common output image by the detector 104 and then separated, or can be generated directly during the readout phase.

[0074] FIG. 5A is a conceptual diagram of a measurement system 100 comprising a TDI sensor (e.g., as detector 104) suitable for capturing an interleaved output image associated with two alternating optical configurations, according to one or more embodiments of the present disclosure. FIG. 5B is a conceptual diagram of a portion of the light collection path 122 of the measurement system 100 of FIG. 5A showing charge transfer, according to one or more embodiments of the present disclosure.

[0075] In one embodiment, the measurement system 100 comprises a cylindrical lens array 504 within the light collection path 122 to focus light (e.g., sample light 120) from the sample 102 onto alternating pixel rows 506 of the TDI sensor 502. In this regard, the measurement system 100 can be configured to expose only a set 508 of pixel rows 506 (e.g., alternating pixel rows 506). The remaining set 510 of pixel rows 506 remains unilluminated.

[0076] In another embodiment, the measurement system 100 includes a slit array (not shown) for blocking the unilluminated set 510 of pixel rows 506. The slit array can be placed anywhere suitable for blocking the unilluminated set 510 of pixel rows 506. For example, the slit array can be placed within the TDI sensor 502 or otherwise integrated. As another example, the slit array can be located in the plane of the light collection path 122. Further, it is contemplated that the measurement system 100 can include a slit array instead of or in addition to the cylindrical lens array 504.

[0077] At this time, the measurement system 100 can perform scanning mode measurement by synchronizing the charge transfer rate of the TDI sensor 502 and the movement of the sample 102 along the scanning direction 512, as in a normal TDI setup, except that images are generated alternately using two different optical configurations at the clocking rate of the TDI sensor 502. In this regard, the TDI sensor 502 can generate an interleaved output image associated with a single exposure window. Next, the interleaved output image can be split (e.g., by the controller 130) into separate images associated with different optical configurations. In particular, the sequence for forming the interleaved output image can be as follows, but is not essential. First, the measurement system 100 is configured to image the sample 102 using a first optical configuration, where the sample light 120 is converged onto a set 508 of illuminated pixel rows 506. Second, the TDI sensor 502 is clocked to transfer charges from the set 508 of illuminated pixel rows 506 associated with the first optical configuration. At the same time, the measurement system 100 is configured to image the sample 102 using a second optical configuration, where the sample light 120 is converged onto the set 508 of illuminated pixel rows 506 again. Third, the TDI sensor 502 is clocked again to transfer the charges associated with the first optical configuration back to the set 508 of illuminated pixel rows 506. Since the charge transfer rate and the movement of the sample 102 are synchronized, the charges associated with the first optical configuration can accumulate in the set 508 of illuminated pixel rows 506 as normally occurs in TDI operation. Next, this process is repeated such that the alternating output image rows correspond to the first and second optical configurations, respectively. These alternating rows can be split to form two separate images associated with the first and second optical configurations, respectively. Further, it should be noted that the two images can be spatially shifted by half the pixel pitch along the scanning direction.

[0078] However, it should be understood that FIGS. 5 and the associated description are for illustrative purposes only and should not be construed as limiting. For example, FIGS. 5 and the associated description describe a configuration in which the cylindrical lens array 504 converges the sample light 120 onto alternating pixel rows 506 to generate an interleaved output image associated with two optical configurations. However, the techniques described herein can be extended to any number of optical configurations (e.g., N optical configurations, where N is an integer greater than 1). For example, the technique can be extended to support N optical configurations by illuminating pixel rows 506 in groups of N using any combination of cylindrical lens arrays 504 or slit arrays, and then circulating the N optical configurations at a TDI clocking rate in the exposure window of the detector 104.

[0079] In another embodiment, as described above herein, the measurement system 100 can include a detector 104 configured as a multi-tap imaging sensor. In this regard, the charge at each pixel can be directed to any selected tap in the exposure window based on one or more drive signals to the pixel. A multi-tap sensor including an array of multi-tap pixels can generate multiple images, each associated with a different tap of the associated pixels, during a single readout phase. Thus, the measurement system 100 can perform stationary mode measurements by sequentially providing any selected number of optical configurations (e.g., N optical configurations) in the exposure window while the sample 102 is stationary. Further, the controller 130 can be communicatively coupled to the pixels in the multi-tap sensor and can generate drive signals for directing charge from each optical configuration to different taps in the exposure window. Next, the measurement system 100 can read out N images from two or more taps during the readout phase, where the N images correspond to the N optical configurations.

[0080] The subject matter described herein shows different components that are included in or connected to other components. It should be understood that the architecture thus described is merely an example, and that in fact many other configurations can be implemented to achieve the same function. Conceptually, any arrangement of components that achieves the same function is effectively "associated" so that the desired function is achieved. Thus, two components combined to achieve a particular function in this specification can be recognized as being "associated" with each other so that the desired function is achieved, regardless of the architecture or intermediate components. Similarly, two components thus associated can also be considered to be "connected" or "coupled" to each other to achieve the desired function, and any two components capable of such association can also be considered to be "couplable" to each other to achieve the desired function. Specific examples of couplable include, but are not limited to, components that are physically interactable and / or physically interacting, and / or wirelessly interactable and / or wirelessly interacting, and / or logically interactable and / or logically interacting components.

[0081] It is believed that many of the present disclosure, and the attendant advantages, will be understood from the foregoing description. It will also be apparent that various changes may be made in the form, structure, and arrangement of the components without departing from the disclosed subject matter or sacrificing any of the advantages of the disclosed material. The described forms are merely exemplary, and the following claims are intended to imply and encompass such changes. It will also be understood that the invention is defined by the appended claims.

Claims

1. A measurement tool configured to selectively perform measurement in a stationary mode in which one or more measurement targets on a sample do not move during measurement, or in a scanning mode in which one or more measurement targets move during measurement, A translation stage, and a controller communicatively coupled to at least one of one or more detectors, wherein the controller causes one or more processors to Receive the locations of a plurality of measurement targets on the sample to be investigated, Specify the plurality of measurement targets for investigation in the stationary mode or the scanning mode, Based on the specification, instruct the measurement tool to perform measurement on the plurality of measurement targets in the stationary mode or the scanning mode, and Generate measurement data of the sample based on the measurement on the plurality of measurement targets A controller including the one or more processors configured to execute program instructions to cause the above to be performed, Comprising, The measurement tool includes a multi-channel imaging subsystem configured to sequentially provide N optical configurations for imaging a sample at an exposure window of a detector and generate N images of the sample during a readout phase of the detector associated with the exposure window, A specific image among the N images corresponds to a specific optical configuration among the N optical configurations, The detector includes a time delay integration (TDI) sensor for scanning mode measurement, Further comprising a cylindrical lens array configured to direct light emitted from the sample toward N pixel rows of the TDI sensor, The measurement tool is Translating the sample at a charge transfer rate of the TDI sensor, and Sequentially providing the N optical configurations for imaging the sample, wherein a switching time between consecutive optical configurations of the multi-channel imaging subsystem corresponds to the charge transfer rate of the TDI sensor, Using the TDI sensor to generate an interleaved image including the N images in the exposure window, and Separating the interleaved image into the N images A measurement system characterized in that it is configured to perform scanning mode measurement by.

2. The measurement system according to claim 1, wherein the one or more processors are configured to specify the plurality of measurement targets for investigation in the stationary mode or the scanning mode based on at least one of a target type, a target location, a proximity to one or more additional measurement targets among the plurality of measurement targets, or a target density. A measurement system characterized by that.

3. The measurement system according to claim 1, wherein the one or more processors are configured to separate at least some of the plurality of measurement targets specified for investigation in the scanning mode into one or more scanning groups, and a specific scanning group among the one or more scanning groups includes at least two of the plurality of measurement targets measured in a common scan by the measurement tool. A measurement system characterized by that.

4. The measurement system according to claim 3, wherein the one or more processors are configured to separate at least some of the plurality of measurement targets specified for investigation in the scanning mode into one or more scanning groups based on at least one of target densities along a scanning direction. A measurement system characterized by that.

5. The measurement system according to claim 1, wherein the measurement tool exposes the sample to illumination from an illumination source in the exposure window while the sample is stationary without clocking the TDI sensor to transfer charge; generates an image by clocking the TDI sensor to transfer charge row by row when the sample is not exposed to the illumination from the illumination source. configured to perform stationary mode measurement by A measurement system characterized by that.

6. The measurement system according to claim 1, wherein the measurement tool further includes an imaging detector, wherein the measurement tool exposes the sample to illumination from an illumination source in the exposure window while the sample is stationary; reads an image of the sample using the imaging detector after the exposure window. configured to perform static mode measurement by A measurement system characterized by that.

7. The measurement system according to claim 1, wherein the measurement system further comprises a slit array positioned to block pixel rows of the TDI sensor that are not illuminated by the cylindrical lens array.

8. The measurement system according to claim 1, wherein the detector further comprises a multi-tap imaging sensor for stationary mode measurement, the multi-tap imaging sensor having two or more suitable taps, the measurement tool, sequentially providing the N optical configurations to image the sample when the sample is stationary, and the multi-tap imaging sensor being synchronized with a multi-channel illumination source such that different taps of the two or more taps receive charge for each of the N optical configurations in the exposure window; reading out the N images from the multi-tap imaging sensor during a readout phase and configured to perform static mode measurement by a measurement system characterized by the above.

9. Receiving, using one or more processors, locations of a plurality of measurement targets on a sample to be investigated; Specifying, using one or more processors, the plurality of measurement targets for investigation in a stationary mode where one or more measurement targets on the sample do not move during measurement, or a scanning mode where one or more measurement targets move during measurement; Instructing, using one or more processors, a measurement tool to perform measurement measurements on the plurality of measurement targets in the stationary mode or the scanning mode based on the specification via one or more drive signals; Generating, using one or more processors, measurement data of the sample based on the measurement measurements on the plurality of measurement targets including the measurement tool comprising a multi-channel imaging subsystem configured to sequentially provide N optical configurations for imaging the sample at an exposure window of a detector and generate N images of the sample during a readout phase associated with the exposure window, a particular image of the N images corresponding to a particular one of the N optical configurations, the detector comprising a time delay integration (TDI) sensor for scanning mode measurement Further comprising a cylindrical lens array configured to direct light emitted from the sample toward each pixel row of N of the TDI sensors, The measurement tool, Translating the sample at the charge transfer rate of the TDI sensor, Providing the N optical configurations for imaging the sample sequentially, wherein a switching time between successive optical configurations of the multi-channel imaging subsystem corresponds to the charge transfer rate of the TDI sensor, Generating an interleaved image including the N images in the exposure window using the TDI sensor, Separating the interleaved image into the N images A measurement method characterized by performing the scanning mode measurement by the above.

10. A multi-channel imaging subsystem, comprising: A light source, One or more illumination optical systems configured to direct illumination from the light source toward a sample, One or more condenser optical systems configured to collect light emitted from the sample in response to the illumination from the light source, and A detector configured to generate two or more images of the sample in an exposure window, A multi-channel imaging subsystem comprising: A controller communicably coupled to the detector, the controller causing one or more processors to: Generate one or more drive signals for at least one of the light source, the one or more illumination optical systems, the one or more condenser optical systems, or the detector to sequentially provide N optical configurations of the multi-channel imaging subsystem within the exposure window of the detector, N being a selected integer greater than 1, the detector generating N images of the sample during a readout phase associated with the exposure window, a particular one of the N images corresponding to a particular one of the N optical configurations, and Generate measurement data associated with the sample based on the N images of the sample A controller including the one or more processors configured to execute program instructions to cause the above, Comprising: The detector includes a time delay integration (TDI) sensor, the sample stage is configured to translate the sample at the charge transfer rate of the TDI sensor, and the switching time between successive optical configurations of the multi-channel imaging subsystem corresponds to the charge transfer rate of the TDI sensor. A measurement system characterized by this.

11. The measurement system according to claim 10, further comprising a cylindrical lens array configured to direct light emitted from the sample toward each N pixel rows of the TDI sensor, wherein the TDI sensor generates an interleaved image including the N images in the exposure window. A measurement system characterized by this.

12. The measurement system according to claim 11, further comprising a slit array positioned to block pixel rows of the TDI sensor not illuminated by the cylindrical lens array. A measurement system characterized by this.

13. The measurement system according to claim 10, further comprising a slit array positioned to pass light through each N pixel rows of the TDI sensor and block the remaining pixel rows of the TDI sensor, wherein the TDI sensor generates an interleaved image including the N images in the exposure window. A measurement system characterized by this.

14. The measurement system according to claim 13, wherein the slit array is positioned on the TDI sensor. A measurement system characterized by this.

15. The measurement system according to claim 13, wherein the slit array is positioned on the field plane of the measurement system. A measurement system characterized by this.

16. The measurement system according to claim 10, further comprising a slit array positioned to block pixel rows of the TDI sensor not illuminated by the cylindrical lens array. A measurement system characterized by this.

17. The measurement system according to claim 10, wherein the detector includes a multi-tap imaging sensor having two or more taps suitable for generating at least N images in the exposure window, and the multi-tap imaging sensor is synchronized with a multi-channel illumination source such that the multi-tap imaging sensor generates separate images associated with each of the N optical configurations in the exposure window. A measurement system characterized by this.

18. The measurement system according to claim 10, wherein a specific one of the N optical components includes the spectrum of illumination.

19. The measurement system according to claim 18, wherein the multi-channel illumination source comprises a broadband light source, and at least one spectral filter and is characterized by the measurement system.

20. The measurement system according to claim 19, wherein the at least one spectral filter is tunable.

21. The measurement system according to claim 18, wherein the multi-channel illumination source comprises two or more illumination sources having different spectra.

22. The measurement system according to claim 10, wherein the multi-channel illumination source includes at least one spectral filter, and a specific one of the N optical components includes the spectrum of illumination and is characterized by the measurement system.

23. The measurement system according to claim 10, wherein the multi-channel illumination source includes at least one polarizer, and a specific one of the N optical components includes the polarization of illumination and is characterized by the measurement system.

24. The measurement system according to claim 10, wherein the multi-channel illumination source includes a variable lens, and a specific one of the N optical components includes the location of the imaging plane with respect to the surface of the sample and is characterized by the measurement system.

25. The measurement system according to claim 24, wherein the variable lens includes at least one of a variable focus lens or a translation stage configured to adjust the position of the lens.

26. The measurement system according to claim 10, wherein the multi-channel illumination source includes two or more channels having different optical paths, and each of the two or more channels includes one or more optical components for providing illumination having a specific one of the N optical components.

27. The measurement system according to claim 26, wherein the multi-channel illumination source includes a beam combiner that routes illumination in each of the two or more channels to a common optical column. In at least one of the two or more channels, one or more shutters that selectively block illumination so that it does not reach the common optical column further comprising a measurement system characterized by this.

28. The measurement system according to claim 27, wherein the one or more shutters include at least one of a mechanical shutter, an electro-optical shutter, or an acousto-optical shutter. A measurement system characterized by this.

29. The measurement system according to claim 10, wherein a specific optical configuration among the N optical configurations includes the imaging configuration of the detector. A measurement system characterized by this.

30. The measurement system according to claim 29, wherein the parameters of the imaging configuration of the detector include at least one of gain or exposure time. A measurement system characterized by this.

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