Sensitive optical metrology in scanning and static modes

Abstract

A metrology system may include a metrology tool for selectively performing metrology measurements in a static mode in which one or more metrology targets on a sample are stationary during measurement or in a scanning mode in which one or more metrology targets are in motion during measurement, and a controller communicatively coupled to a translation stage and at least one of one or more detectors. The controller may receive a position of a metrology target on the sample to be inspected, designate the metrology target for inspection using the static mode or the scanning mode, direct the metrology tool to perform metrology measurements on the metrology target in the static mode or the scanning mode based on the designation, and generate metrology data for the sample based on the metrology measurements on the metrology target.

Description

Technical Field

[0001] The present disclosure relates generally to optical metrology and more particularly to optical metrology in scanning and static modes. Background Art

[0002] Metrology systems typically generate metrology data associated with a sample by measuring or otherwise verifying dedicated metrology targets distributed across the sample. Furthermore, different metrology tools may be designed to verify metrology targets using different techniques. For example, some metrology tools may be designed to verify targets when the metrology targets are static within a field of view. Thus, such tools may verify multiple metrology targets across a sample using a move and measure (MAM) mode of operation, in which the sample is translated to place a metrology target of interest within a measurement field of view, measurements are taken while the sample is static, and then the sample is translated to place additional metrology targets of interest in the measurement field of view. By way of another example, some metrology tools may be designed to verify metrology targets while the sample is in motion (e.g., a scanning mode of operation).

[0003] The increased demand for smaller semiconductor devices has resulted in a corresponding increase in the need for accurate and efficient metrology. However, metrology tools with dedicated MAM or scanning modes may provide ineffective verification of metrology targets distributed across samples.

[0004] Additionally, regardless of the operating mode, a metrology tool may inspect a particular metrology target using one or more optical configurations (e.g., illumination spectrum, polarization, or the like) and generate metrology data based on the combined inspection to achieve a desired measurement sensitivity. However, variations in measurement conditions between inspections with different optical configurations may limit the achievable measurement sensitivity.

[0005] Therefore, it is desirable to provide systems and methods that address the above-mentioned deficiencies. Summary of the invention

[0006] According to one or more illustrative embodiments of the present disclosure, a metrology system is disclosed. In one illustrative embodiment, the system includes a metrology tool configured to selectively perform metrology measurements in a static mode in which one or more metrology targets on a sample are stationary during measurement or in a scanning mode in which one or more metrology targets are in motion during measurement. In another illustrative embodiment, the system includes a controller communicatively coupled to a translation stage and at least one of one or more detectors. In another illustrative embodiment, the controller receives a position of a metrology target on the sample to be inspected. In another illustrative embodiment, the controller specifies the metrology target for inspection using the static mode or the scanning mode. In another illustrative embodiment, the controller directs the metrology tool to perform metrology measurements on the metrology target in the static mode or the scanning mode based on the designation. In another illustrative embodiment, the controller generates metrology data of the sample based on the metrology measurements of the multiple metrology targets.

[0007] According to one or more illustrative embodiments of the present disclosure, a metrology method is disclosed. In one illustrative embodiment, the method includes receiving a position of a metrology target on a sample to be inspected. In another illustrative embodiment, the method includes specifying the metrology target for inspection using a static mode in which one or more metrology targets on the sample are stationary during measurement or a scanning mode in which one or more metrology targets are in motion during measurement. In another illustrative embodiment, the method includes directing the metrology tool to perform metrology measurements on the metrology target in the static mode or the scanning mode based on the specification via one or more drive signals. In another illustrative embodiment, the method includes generating metrology data of the sample based on the metrology measurements of the metrology target.

[0008] According to one or more illustrative embodiments of the present disclosure, a metrology system is disclosed. In one illustrative embodiment, the system includes a multi-channel imaging subsystem. In another illustrative embodiment, the multi-channel imaging subsystem includes an illumination source. In another illustrative embodiment, the multi-channel imaging subsystem includes one or more illumination optical devices for directing illumination from the illumination source to a sample. In another illustrative embodiment, the multi-channel imaging subsystem includes one or more light collection optical devices for collecting light emitted from the sample in response to the illumination from the illumination source. In another illustrative embodiment, the multi-channel imaging subsystem includes a detector for generating two or more images of the sample in an exposure window. In another illustrative embodiment, the system includes a controller communicatively coupled to the detector. In another illustrative embodiment, the controller generates one or more drive signals for at least one of the illumination source, the one or more illumination optical devices, the one or more light collection optical devices, 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 illustrative embodiment, the detector generates N images of the sample during a readout phase associated with the exposure window, wherein a particular image of the N images corresponds to a particular optical configuration of the N optical configurations. In another illustrative embodiment, the controller generates metrology data associated with the sample based on the N images of the sample.

[0009] It should be understood that both the above general description and the following detailed description are exemplary and explanatory only and do not necessarily limit the present invention. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and together with the general description serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Many of the advantages of the present disclosure may be better appreciated by those skilled in the art by referring to the accompanying drawings.

[0011] Figure 1 is a block diagram of a metering system according to one or more embodiments of the present disclosure.

[0012] Figure 2 is a flowchart illustrating steps for performing a method for efficient metering disclosed in accordance with one or more embodiments of the present disclosure.

[0013] Figure 3 is a conceptual top view of metrology targets distributed across a sample in accordance with one or more embodiments of the present disclosure.

[0014] Figure 4is a conceptual diagram of a multi-channel illumination source configured to sequentially generate illumination having two or more optical configurations along a common optical column in accordance with one or more embodiments of the present disclosure.

[0015] Figure 5A is a conceptual diagram of a metrology system including a TDI sensor adapted to capture interleaved output images associated with two alternating optical configurations in accordance with one or more embodiments of the present disclosure.

[0016] Figure 5B is an illustration of charge transfer according to one or more embodiments of the present disclosure Figure 5A Conceptual view of a portion of the metering system's light collection path. DETAILED DESCRIPTION

[0017] Reference will now be made in detail to the disclosed subject matter illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments set forth herein are to be considered illustrative rather than restrictive. One of ordinary skill in the art will readily appreciate that various changes and modifications in form and details may be made without departing from the spirit and scope of the present disclosure.

[0018] Embodiments of the present disclosure relate to systems and methods for high throughput and high sensitivity optical metrology.

[0019] Some embodiments of the present disclosure relate to optical metrology using dynamically selectable operating modes. For example, a metrology system may be capable of having both a static (e.g., MAM) operating mode for measuring metrology targets when a sample is static and a scanning operating mode for measuring metrology targets when a sample is in motion.

[0020] Static mode may consist of: translating the sample until a metrology target is placed within the measurement field of view; waiting for the position of the sample to settle; performing a measurement (e.g., generating an image or the like); translating the sample to place a new metrology target within the measurement field of view; and repeating the process. In contrast, scanning mode may consist of: translating the sample to a desired starting position; scanning the sample along a controlled path including one or more metrology targets during measurement to reach a desired end position; translating the sample to a new starting position; and repeating the process.

[0021] It should be recognized herein that the efficiency of inspection using static and scanning modes may depend on the specific layout and type of metrology targets on the sample. For example, the scanning mode of operation may be well suited for (but not limited to) situations where multiple metrology targets are closely spaced along a line. This configuration is common in, for example, intra-die locations (e.g., die lanes) of semiconductor samples. In this regard, the constant scanning provided by the scanning mode can effectively inspect multiple targets. By way of another example, the static mode may be well suited for (but not limited to) situations where the metrology targets are sparsely distributed across the wafer and / or are not distributed in a regular pattern suitable for line scanning.

[0022] Additional embodiments of the present disclosure relate to specifying or otherwise selecting which operating mode to use for a particular metrology target distributed across a sample. It should be recognized herein that the distribution of metrology targets across a single sample may include some areas that are well suited for static mode inspection and other areas that are well suited for scanning mode inspection. Therefore, specifying certain metrology targets for static mode inspection and other metrology targets for scanning mode inspection may facilitate high throughput inspection of the sample as a whole.

[0023] In some embodiments, a metrology system receives the locations of a plurality of metrology targets distributed across a sample and specifies each of the metrology targets for inspection using a selected mode (e.g., static or scanning). The metrology system may use various metrics to determine a mode for a particular target. For example, the metrology system may specify based on target type, target location, proximity to one or more additional metrology targets in a plurality of metrology targets, or target density. Furthermore, the metrology system may specify based on a weighting function in which relative weights are provided for a plurality of metrics.

[0024] Some embodiments of the present disclosure relate to rapidly generating multiple measurements of a metrology target using multiple optical configurations within a single exposure window of a detector. It should be recognized herein that an optical metrology system typically generates one or more images of a sample that can be analyzed to determine a metrology measurement of interest (e.g., an overlay metrology measurement, a critical dimension (CD) measurement, a sidewall angle (SWA) measurement, identification of a defect, or the like). In this regard, a metrology system may typically include a detector positioned at a field plane (e.g., a plane conjugate to the sample for generating an image of one or more features on the sample), a pupil plane (e.g., for generating a pupil image associated with the angle at which light is emitted from the sample), or both.

[0025] In addition, it may be advantageous to generate multiple images of a particular optical target using different optical configurations. For purposes of the present disclosure, an optical configuration may include a set of specific illumination, light collection, or imaging parameters used to generate an image. For example, an optical configuration may include, but is not limited to, a spectrum of the illumination beam, a spectrum of light collected from a sample used to generate an image, a polarization of the illumination beam, a polarization of light collected from a sample used to generate an image, a position of the image plane relative to the surface of the sample, an opening diameter of one or more stops or pupils (e.g., a field stop, an aperture stop, or the like), a position of one or more stops or pupils (e.g., which may be used to adjust telecentricity), or detector settings (e.g., gain, exposure time, or the like).

[0026] The image quality associated with a particular metrology target may depend on the interaction between the imaging system and the characteristics of the particular metrology target. For example, the absorption, reflection, diffraction and / or scattering of light from the metrology target may vary based on the composition, size and layout of features in the metrology target, as well as the wavelength and polarization of the illumination beam.

[0027] Multiple images of a target produced using different optical configurations may be utilized in various ways to achieve a desired performance level (e.g., a desired sensitivity, signal-to-noise ratio (SNR), a desired image contrast, or the like). For example, producing multiple images of a target using different optical configurations may facilitate selecting a particular optical configuration (e.g., in a processing step) for each metrology that produces an image having image quality within a selected specification. By way of another example, an algorithm for producing metrology measurements may incorporate multiple sample images produced using a set of known different optical configurations.

[0028] It is further recognized herein that it is often desirable to produce images using different optical configurations under the same conditions. However, metrology systems often contain temporally varying error sources that result in changes in the optical configuration over time. For example, the spectrum or beam profile of an illumination beam may exhibit temporal jitter or drift. By way of another example, a translation stage that holds a sample may similarly exhibit temporal jitter or drift. This temporal error source may be particularly problematic for systems that utilize multiple images produced using different optical configurations, where differences between images due to system-level variations may manifest as measurement errors associated with the sample.

[0029] Therefore, some embodiments of the present disclosure are directed to forming images using multiple optical configurations within a common exposure window. For example, a metrology system can quickly switch between different optical configurations.

[0030] For example, a typical metrology system may generate an image by exposing a sample using a given optical configuration and correspondingly exposing pixels of a detector during an exposure window. A typical metrology system may then read out the charge stored to form the image associated with the given optical configuration.

[0031] In an embodiment of the present disclosure, a metrology system can generate multiple images of a sample using different optical configurations in an exposure window by rapidly changing the optical configuration during a single exposure window and generating multiple images associated with the different optical configurations in a common readout phase. In this regard, the duration between images of the sample associated with different optical configurations can be substantially minimized. Thus, time-varying error sources can affect each of the different images in substantially the same manner.

[0032] In some embodiments, the metrology system includes a scanning sensor, such as, but not limited to, a line sensor or a time-delay integration (TDI) sensor for generating a continuous output image (e.g., a strip image) as the sample is translated through the measurement field. Thus, a metrology system configured in accordance with the present disclosure may sequentially cycle through different optical configurations and synchronize the translation speed of the sample with the clock rate of the scanning sensor so that each row of pixels corresponds to a different optical configuration. In this regard, the output image may be composed of interleaved images, each associated with a different optical configuration. The output image may then be separated into multiple separate images in a post-processing step.

[0033] In some embodiments, the metrology system includes a static multi-tap imaging sensor. In this regard, each pixel may include two or more taps, where the charge stored in the pixel can be directed to any tap by a drive signal. A metrology system configured according to the present disclosure can sequentially cycle through different optical configurations and synchronize the drive signals of the pixels during an exposure window to direct the charge associated with the different optical configurations to a dedicated tap. Multiple images can then be generated from the multiple taps during a subsequent readout phase.

[0034] Reference Figures 1 to 5B , systems and methods for efficient and sensitive metering are described in more detail.

[0035] Figure 1 1 is a block schematic diagram of a metrology system 100 according to one or more embodiments of the present disclosure. The metrology system 100 can generate one or more images of the sample 102 on at least one detector 104 using any method known in the art. In one embodiment, the detector 104 is positioned at a field plane to generate an image of one or more features on the sample 102. In another embodiment, the detector 104 is positioned at a pupil plane to generate an image based on the angle at which light is emitted from the sample 102 (e.g., based on reflection, diffraction, scattering, or the like). In this regard, the metrology system 100 can operate as a scatterometry-based metrology tool.

[0036] In one embodiment, the metrology system 100 includes an illumination source 106 for generating an illumination beam 108. The illumination beam 108 may 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, or infrared (IR) radiation. The illumination source 106 may further generate the illumination beam 108 to include any range of selected wavelengths. In another embodiment, the illumination source 106 may include a spectrally tunable illumination source for generating the illumination beam 108 having a tunable spectrum.

[0037] The illumination source 106 may further generate an illumination beam 108 having any temporal profile. For example, the illumination source 106 may generate a continuous illumination beam 108, a pulsed illumination beam 108, or a modulated illumination beam 108. Additionally, the illumination beam 108 may be delivered from the illumination source 106 via free space propagation or guided light (e.g., an optical fiber, a light pipe, or the like).

[0038] In another embodiment, the illumination source 106 directs the illumination beam 108 to the sample 102 via an illumination path 110. The illumination path 110 may 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 may 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 shutters, electro-optical shutters, acousto-optical shutters, or the like). By way of another example, the one or more illumination optical components 114 may include an aperture stop for controlling the illumination angle on the sample 102 and / or a field stop for controlling the spatial extent of the illumination on the sample 102. In one example, the illumination path 110 includes an aperture stop positioned at a plane conjugate to the back focal plane of the objective lens 116 to provide telecentric illumination of the sample. In another embodiment, the metrology system 100 includes an objective lens 116 for focusing the illumination beam 108 onto the sample 102 .

[0039] In another embodiment, the sample 102 is disposed on a sample stage 118. The sample stage 118 may include any device suitable for positioning the sample 102 within the metrology system 100. For example, the sample stage 118 may include any combination of a linear translation stage, a rotation stage, a flip / tilt stage, or the like.

[0040] In another embodiment, the detector 104 is configured to capture radiation (eg, sample light 120) emitted from the sample 102 via a collection path 122. For example, the collection path 122 may include (but need not include) a collection lens (eg, Figure 1) or one or more additional collection path lenses 124. In this regard, detector 104 can receive radiation reflected or scattered from sample 102 (e.g., via specular reflection, diffuse reflection, and the like) or generated by sample 102 (e.g., luminescence associated with absorption of illumination beam 108, or the like).

[0041] The collection path 122 may further include any number of collection optical components 126 for directing and / or modifying the illumination collected by the objective 116, including, but not limited to, one or more collection path lenses 124, one or more filters, one or more polarizers, or one or more beam stops. Additionally, the collection path 122 may include a field stop for controlling the spatial extent of the sample imaged onto the detector 104 or an aperture stop for controlling the angular extent of the illumination from the sample used to generate the image on the detector 104. In another embodiment, the collection path 122 includes an aperture stop positioned in a plane conjugate to the focal plane after the optical element (objective 116) to provide telecentric imaging of the sample.

[0042] The detector 104 may include any type of optical detector known in the art suitable for measuring illumination received from the sample 102. For example, the detector 104 may include a sensor suitable for generating one or more images of the static sample 102 (e.g., in a static operating mode), such as, but 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. In addition, the detector 104 may 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 the multi-tap pixel may be directed to any selected tap during an exposure window based on one or more drive signals to the pixel. Thus, during a single readout phase, a multi-tap sensor including a multi-tap pixel array may generate multiple images, each image being associated with a different tap of an associated pixel. In addition, for the purposes of this disclosure, a tap of a multi-tap sensor may refer to an output tap connected to an associated pixel. In this regard, reading out each tap of the multi-tap sensor (e.g., in a readout phase) may generate a separate image.

[0043] By way of another example, the detector 104 may include a sensor adapted to generate one or more images of the sample 102 in motion (e.g., a scanning mode of operation). For example, the detector 104 may include a line sensor that includes a row of pixels. In this regard, the metrology system 100 may generate a continuous image (e.g., a stripe image) one row at a time by translating the sample 102 through the measurement field of view in a scanning direction perpendicular to the row of pixels and continuously clocking the line sensor during continuous exposure windows.

[0044] In another example, the detector 104 may include a TDI sensor that includes a plurality of pixel rows and a readout row. The TDI sensor may operate in a similar manner to a line sensor, except that a clock signal may continuously move charge from one pixel row to the next pixel row until the charge reaches the readout row (where a row of an image is generated). By synchronizing the charge transfer (e.g., based on a clock signal) with the movement of the sample along the scan direction, charge may continue to accumulate across the pixel rows to provide a relatively higher signal-to-noise ratio than a line sensor.

[0045] In another embodiment, the detector 104 may include a spectral detector adapted to identify wavelengths of radiation emitted from the sample 102. In another embodiment, the metrology system 100 may include multiple detectors 104 (e.g., associated with multiple beam paths generated by one or more beam splitters) for facilitating multiple metrology measurements by the metrology system 100. For example, the metrology system 100 may include one or more detectors 104 adapted for static mode imaging and one or more detectors 104 adapted for scanning mode imaging. In another embodiment, the metrology system 100 may include one or more detectors 104 adapted for both static and scanning imaging modes. For example, a TDI sensor may be operated in a static mode by not clocking the TDI sensor to transfer charge between rows of pixels during an exposure window. Then, once the exposure window stops (e.g., via a shutter, turning off the illumination source 106, or the like) and additional light is not incident on the pixels, the TDI sensor may be clocked to transfer charge line by line to the readout rows to produce an image having a length equal to the number of rows of pixels.

[0046] In one embodiment, as in Figure 1 , the metrology system 100 includes a beam splitter 128 oriented so that the objective 116 can simultaneously direct the illumination beam 108 to the sample 102 and collect radiation emitted from the sample 102. In this regard, the metrology system 100 can be configured in an epi-illumination mode.

[0047] In another embodiment, the angle of incidence of the illumination beam 108 on 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 angle of incidence of the illumination beam 108 on the sample 102. In this regard, the illumination beam 108 can have a normal path through the beam splitter 128 and the objective lens 116 such that the illumination beam 108 has a normal angle of incidence on the sample 102. By way of another example, the angle of incidence of the illumination beam 108 on the sample 102 can be controlled by modifying the position and / or angle of the illumination beam 108 on the beam splitter 128 (e.g., by means of a rotatable mirror, a spatial light modulator, a free-form illumination source, or the like). In another embodiment, the illumination source 106 directs one or more illumination beams 108 to the sample 102 at an angle (e.g., a grazing angle, a 45 degree angle, or the like).

[0048] In another embodiment, the metrology 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, the one or more processors 132 of the controller 130 may perform any of the various process steps described throughout the present disclosure. Furthermore, the controller 130 may be configured to receive data including, but not limited to, metrology data (e.g., alignment measurements, images of the sample, pupil images, and the like) or metrology metrics (e.g., accuracy, tool-induced shift, sensitivity, diffraction efficiency, and the like).

[0049] The one or more processors 132 of the controller 130 may include any processing element known in the art. In this sense, the one or more processors 132 may include any microprocessor type device configured to execute algorithms and / or instructions. In one embodiment, the one or more processors 132 may be composed of a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, or any other computer system (e.g., a network-connected computer) configured to execute a program (which is configured to operate the metering system 100) as described throughout this disclosure. It should be further recognized that the term "processor" may be broadly defined to encompass any device having one or more processing elements that execute program instructions from the non-transitory memory medium 134. In addition, the steps described throughout this disclosure may be performed by a single controller 130 or, alternatively, multiple controllers. In addition, the controller 130 may include one or more controllers housed in a common housing or multiple housings. In this way, any controller or combination of controllers may be individually packaged as a module suitable for integration into the metering system 100. Furthermore, the controller 130 may analyze the data received from the detector 104 and feed the data to additional components within the metrology system 100 or external to the metrology system 100 .

[0050] The memory medium 134 may include any storage medium known in the art suitable for storing program instructions that can be executed by the associated one or more processors 132. For example, the memory medium 134 may include a non-transitory memory medium. By way of another example, the memory medium 134 may include, but is not limited to, a read-only memory, a random access memory, a magnetic or optical storage device (e.g., a disk), a tape, a solid-state disk, and the like. It should be further noted that the memory medium 134 may be housed in a common controller housing with the one or more processors 132. In one embodiment, the memory medium 134 may be remotely located relative to the physical location of the one or more processors 132 and the controller 130. For example, the one or more processors 132 of the controller 130 may access a remote memory (e.g., a server) that is accessible via a network (e.g., the Internet, an intranet, and the like). Therefore, the above description should not be construed as limiting the present invention but is merely illustrative.

[0051] In another embodiment, the controller 130 is communicatively coupled to one or more elements of the metrology system 100. In this regard, the controller 130 may transmit data and / or receive data from any component of the metrology system 100. Furthermore, the controller 130 may direct or otherwise control any component of the metrology 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. Furthermore, the controller 130 may provide one or more drive signals to the detector 104 to implement any detection techniques described herein, such as, but not limited to, providing a clock signal for controlling an exposure and / or readout window, a clock signal for transferring charge between pixel rows of a TDI sensor, a drive signal to a multi-tap sensor to direct charge to a specific tap, or the like. By way of another example, the controller 130 may be communicatively coupled to any combination of components, including, but not limited to, the illumination source 106, the illumination optical component 114, the collection optical component 126, the detector 104, or the like, to control an optical configuration associated with an image.

[0052] Reference Figure 2 , a flow chart illustrating steps for performing a method 200 for effective metrology is disclosed in accordance with 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 static (e.g., MAM) measurement mode to effectively verify metrology targets distributed across a sample 102. Applicants should note that the embodiments and implementation techniques previously described herein in the context of a metrology system 100 should be interpreted as extending to the method 200. However, it should be further noted that the method 200 is not limited to the architecture of the metrology system 100.

[0053] In one embodiment, method 200 includes a step 202 of receiving locations of metrology targets on a sample 102 to be inspected. For example, metrology targets may be distributed at various locations across sample 102.

[0054] Figure 3 is a conceptual top view of metrology targets 302 distributed across a sample 102 according to one or more embodiments of the present disclosure. The sample 102 may include metrology targets 302 at various locations across the surface, including but not limited to, in one or more dies 304 or between adjacent dies 304 (e.g., in one or more die lanes 306). Furthermore, a given die 304 or die lane 306 may include any number of metrology targets 302.

[0055] It should be recognized herein that many metrology targets 302 are typically inspected across a sample to provide representative characteristics of the entire surface of the sample 102. Furthermore, various sampling schemes may be used to effectively select which of any available metrology targets 302 will be inspected on a particular sample 102 at a particular time. Thus, the set of locations of metrology targets on the sample 102 to be inspected received in step 202 need not include all of the available metrology targets 302 on the particular sample 102.

[0056] In another embodiment, the method 200 includes a step 204 of specifying metrology targets for inspection using either a static mode or a scanning mode. In this regard, each (or at least some) of the metrology targets 302 to be inspected on the sample 102 may be specified or otherwise ordered for inspection using either a static mode or a scanning mode. In another embodiment, the step 204 includes separating at least some of the metrology targets 302 specified for inspection using a scanning mode into one or more scanning groups. For example, a scanning group may include two or more metrology targets 302 to be inspected in a common scan of the metrology system 100.

[0057] The measurement mode for each particular metrology target 302 may be determined based on any selected metric or combination of metrics.

[0058] In one embodiment, the measurement mode and / or scan group is selected based on the target type. In general, the sample 102 may include multiple types of metrology targets 302. For example, the sample 102 may include, but is not limited to, an overlay metrology target 302, a critical dimension metrology target 302, or a SWA metrology target 302, where each type of metrology target 302 has a different arrangement of features on one or more layers of the sample 102 (e.g., a different target design). In another example, the sample 102 may include multiple metrology targets 302 configured to generate similar metrology data (e.g., overlay, CD, SWA, or the like) but with different designs. Thus, circumstances may better suit a particular measurement mode (e.g., static or scan mode) for some target designs. In this regard, step 204 may include specifying a measurement mode based on the target type for a particular metrology target 302.

[0059] In another embodiment, the measurement mode and / or scan group is selected based on the target density and / or proximity of adjacent metrology targets 302. For example, it may be more efficient to inspect multiple adjacent metrology targets 302 in a scan mode in one or more scans (e.g., a scan swath) to avoid lengthy acceleration, deceleration, and settling times associated with static measurements. By way of another example, it may be more efficient to inspect irregular and / or sparsely distributed metrology targets 302 using a static mode. In particular, in situations where multiple metrology targets 302 cannot be inspected using a common scan of reasonable length, the time associated with performing separate scans for individual targets may be less efficient than a static measurement.

[0060] In another embodiment, the measurement mode and / or scan group is selected based on the target location. It may be the case that certain areas of the sample 102 are better suited for measurement using a particular measurement mode. For example, multiple metrology targets 302 aligned along a narrow die street 306 may be effectively measured in one or more scans in the scanning mode. By way of another example, metrology targets 302 dispersed within one or more dies 304 may be effectively measured in the static mode.

[0061] Step 204 of specifying a metrology target for an inspection using either a static mode or a scanning mode may be performed locally or remotely to a particular metrology tool. For example, where step 204 is performed remotely, the location of the metrology target 302 (e.g., associated with step 202) and the associated specified measurement mode (e.g., associated with step 204) may be located in a sampling recipe (e.g., a sampling plan) received by the metrology tool.

[0062] In another embodiment, the method 200 includes step 206 of performing metrology measurements on a plurality of metrology targets in a static mode or a scanning mode based on the designation.

[0063] The metrology tool may include any type of metrology tool known in the art suitable for performing both static and scanning mode measurements.

[0064] In one embodiment, the metrology tool includes a TDI sensor, such as detector 104. In this regard, the metrology tool can perform scan mode measurements by: exposing sample 102 using illumination from an illumination source, such as illumination source 106, during an exposure window; synchronizing the TDI sensor with the movement of the sample during the exposure window; and generating an image line by line during the movement of sample 102.

[0065] In another embodiment, the metrology tool may perform static mode measurements by: exposing the sample using illumination from an illumination source without clocking the TDI sensor to transfer charge during an exposure window when the sample is static; and clocking the TDI sensor to transfer charge row by row to produce an image when the sample is not exposed to illumination from the illumination source.

[0066] In another embodiment, the metrology tool may perform static mode measurements by exposing the sample using illumination from an illumination source while the sample is static during an exposure window; and reading out an image of the sample using an imaging detector after the exposure window.

[0067] In another embodiment, the method 200 includes a step 208 of generating metrology data of the sample based on metrology measurements of the plurality of metrology targets. For example, the step 208 may include generating any type of metrology data (including but not limited to overlay metrology data, CD metrology data, or SWA metrology data) based on the verified metrology target 302.

[0068] Reference Figures 4 to 5B , a system and method for high-sensitivity metrology measurement are described in more detail according to one or more embodiments of the present disclosure.

[0069] As previously described herein, in some embodiments, the metrology system 100 generates multiple images of a sample using different optical configurations in a single exposure window of the detector 104. The images may include any combination of field plane and pupil plane images. Furthermore, the multiple images may be generated in static mode and / or scanning mode. In this regard, the metrology system 100 may provide dynamic selection of static or scanning mode measurements (e.g., as Figure 2 ) and provide multiple images of a sample using different optical configurations in either static mode or scanning mode in a single exposure window. However, it should be recognized herein that the metrology system 100 can be configured only for static and / or scanning mode operation within the spirit and scope of the present disclosure.

[0070] The metrology system 100 may generate alternating optical configurations for imaging the sample 102 using any technique known in the art.

[0071] In one embodiment, the metrology system 100 can adjust one or more components in the illumination path 110 to produce a plurality of optical configurations.

[0072] For example, the illumination source 106 may be configured as a multi-channel illumination source for sequentially generating illumination having two or more optical configurations. In some embodiments, the controller 130 may be communicatively coupled to any combination of components in the metrology system 100 and may control the components (e.g., via drive signals) to provide multiple optical configurations.

[0073] Figure 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 in accordance with one or more embodiments of the present disclosure.

[0074] 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 light from the channels 404 into a common optical column 408. In addition, any channel 404 may include separate components for providing individually tunable optical profiles. For example, any channel 404 may include a spectral filter 410 for passing a selected portion of the spectrum of the illumination from the broadband light source 402, a shutter 412, one or more neutral density filters, one or more apertures (e.g., used as field or aperture stops), or one or more polarizers.

[0075] In another embodiment, although not shown, the multi-channel illumination source 106 may include one or more tunable optical elements (eg, tunable spectral filters, shutters, apertures, polarizers, or the like) along a single common optical column 408 .

[0076] In another embodiment, the metrology system 100 may adjust one or more components of the collection light path 122 to produce multiple optical configurations. For example, the metrology system 100 may adjust (e.g., via the controller 130) 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 collection light path 122 to produce multiple optical configurations. By way of another example, the metrology system 100 may adjust one or more parameters of the detector 104, such as (but not limited to) gain or exposure window (e.g., integration time), to produce multiple optical configurations.

[0077] The metrology system 100 may include any type of detector 104 suitable for generating multiple images associated with different optical configurations within a single exposure window of the detector 104. The multiple images may be interleaved by the detector 104 into a common output image and then separated or they may be generated directly during the readout phase.

[0078] Figure 5A is a conceptual diagram of a metrology system 100 including a TDI sensor 502 (eg, as a detector 104 ) adapted to capture interleaved output images associated with two alternating optical configurations, in accordance with one or more embodiments of the present disclosure.

[0079] Figure 5B is an illustration of charge transfer according to one or more embodiments of the present disclosure Figure 5A 1. Conceptual view of a portion of the light collection path 122 of the metrology system 100.

[0080] In one embodiment, the metrology system 100 includes a cylindrical lens array 504 in the light collection path 122 for focusing light from the sample 102 (e.g., sample light 120) onto alternating pixel rows 506 of the TDI sensor 502. In this regard, the metrology 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.

[0081] In another embodiment, the metrology system 100 includes a slit array (not shown) for blocking the unilluminated set 510 of the pixel rows 506. The slit array may be placed at any location suitable for blocking the unilluminated set 510 of the pixel rows 506. For example, the slit array may be placed on the TDI sensor 502 or otherwise integrated within the TDI sensor 502. By way of another example, the slit array may be positioned in the field plane of the light collection path 122. Furthermore, it is contemplated herein that the metrology system 100 may include a slit array in place of or in addition to the cylindrical lens array 504.

[0082] The metrology system 100 may then perform scan mode measurements by synchronizing the charge transfer rate of the TDI sensor 502 with the motion of the sample 102 along the scan direction 512 as in a typical TDI setup, but alternately generating images using two different optical configurations at the clock rate of the TDI sensor 502. In this regard, the TDI sensor 502 may generate an interlaced output image associated with a single exposure window. The interlaced output image may then be separated (e.g., by the controller 130) into separate images associated with different optical configurations. In particular, the sequence for forming the interlaced output image may be (but need not be) as follows. First, the metrology system 100 is configured to image the sample 102 using a first optical configuration, wherein the sample light 120 is focused onto a set 508 of illuminated pixel rows 506. Second, the TDI sensor 502 is clocked to transfer charge associated with the first optical configuration out of the set 508 of illuminated pixel rows 506. At the same time, the metrology system 100 is configured to image the sample 102 using a second optical configuration, wherein the sample light 120 is again focused onto the set 508 of illuminated pixel rows 506. Third, the TDI sensor 502 is again clocked to transfer the charge associated with the first optical configuration back to the set 508 of illuminated pixel rows 506. Since the charge transfer rate is synchronized with the motion of the sample 102, the charge associated with the first optical configuration can be accumulated in the set 508 of illuminated pixel rows 506 as would normally occur in TDI operation. This process is then repeated so that alternating rows of the output image correspond to the first and second optical configurations, respectively. These alternating rows can then be segmented to form two separate images associated with the first and second optical configurations, respectively. Furthermore, it should be noted that the two images can be spatially shifted along the scan direction by half the pixel pitch.

[0083] However, it should be understood that FIG. 5 and the associated description are provided for illustrative purposes only and should not be construed as limiting. For example, FIG. 5 and the associated description describe a configuration in which a cylindrical lens array 504 focuses sample light 120 onto alternating pixel rows 506 to produce an interlaced output image associated with two optical configurations. However, the methods described herein may be extended to any number of optical configurations (e.g., N optical configurations, where N is an integer greater than 1). For example, the methods may be extended to support N optical configurations by illuminating every Nth pixel row 506 using any combination of a cylindrical lens array 504 or a slit array and sequentially cycling through the N optical configurations at the TDI timing rate during the exposure window of the detector 104.

[0084] In another embodiment, as previously described herein, the metrology system 100 may include a detector 104 configured as a multi-tap imaging sensor. In this regard, the charge in each pixel may be directed to any selected tap based on one or more drive signals to the pixel during an exposure window. During a single readout phase, a multi-tap sensor including an array of multi-tap pixels may generate multiple images, each image associated with a different tap of an associated pixel. Thus, the metrology system 100 may perform static mode measurements by sequentially providing any selected number of optical configurations (e.g., N optical configurations) while the sample 102 is static during an exposure window. Furthermore, the controller 130 may be communicatively coupled to the pixels in the multi-tap sensor and may generate drive signals during the exposure window to direct the charge from each optical configuration to a different tap. Then, the metrology system 100 may read out N images from two or more taps during a readout phase, where the N images correspond to the N optical configurations.

[0085] The subject matter described herein sometimes illustrates different components contained within or connected to other components. It should be understood that such depicted architectures are merely exemplary, and in fact many other architectures that achieve the same functionality can be implemented. In a conceptual sense, any arrangement of components used to achieve the same functionality is effectively "associated" so that the desired functionality is achieved. Therefore, any two components combined in this article to achieve a specific functionality can be considered to be "associated" with each other so that the desired functionality is achieved without regard to architecture or intermediate components. Similarly, any two components so associated can also be considered to be "connected or "coupled" to each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be "coupleable" to each other to achieve the desired functionality. Specific examples of coupleability include (but are not limited to) physically interactable and / or physically interacting components and / or wirelessly interactable and / or wirelessly interacting components and / or logically interactable and / or logically interacting components.

[0086] It is believed that the present disclosure and many of its attendant advantages will be understood from the foregoing description, and it will be appreciated that various changes may be made to the form, construction, and arrangement of components without departing from the disclosed subject matter or sacrificing all of its material advantages. The forms described are merely illustrative, and it is intended that such changes be covered and included by the appended claims. Furthermore, it should be understood that the invention is defined by the appended claims.

Claims

1. A metering system comprising: A metrology tool configured to selectively perform metrology measurements in a static mode in which one or more metrology targets on a sample are stationary during the measurement or in a scanning mode in which one or more metrology targets are in motion during the measurement, wherein the metrology tool comprises a TDI sensor including a plurality of pixel rows and a multi-channel imaging subsystem configured to sequentially provide N optical configurations for imaging a sample in an exposure window of a detector and to generate N images of the sample during a readout phase of the detector associated with the exposure window, wherein N is an integer greater than 1, wherein a particular image of the N images corresponds to a particular optical configuration of the N optical configurations, wherein one or more optical devices of the multi-channel imaging subsystem comprises a cylindrical lens array configured to direct light emitted from the sample to every Nth pixel row of the TDI sensor, wherein the metrology tool is configured to perform scan mode measurements by: translating the sample along a scan direction perpendicular to the row of pixels at a charge transfer rate of the TDI sensor; sequentially providing the N optical configurations for imaging the sample, 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 comprising the N images during the exposure window using the TDI sensor; and Separating the interlaced image into the N images; and a controller communicatively coupled to the translation stage and the TDI sensor, the controller comprising one or more processors configured to execute program instructions, the program instructions causing the one or more processors to: receiving positions of a plurality of metrology targets on the sample to be inspected; specifying the plurality of metrology targets for inspection using the static mode or the scanning mode; directing the metrology tool to perform metrology measurements on the plurality of metrology targets in the static mode or the scanning mode based on the designation; and Metrology data for the sample is generated based on the metrology measurements of the plurality of metrology targets.

2. The metrology system of claim 1 , wherein the one or more processors are configured to designate the plurality of metrology targets for inspection using the static mode or the scanning mode based on at least one of target type, target location, proximity to one or more additional metrology targets in the plurality of metrology targets, or target density.

3. The metrology system of claim 1 , wherein the one or more processors are configured to separate at least some of the plurality of metrology targets specified for inspection using the scan mode into one or more scan groups, wherein a particular scan group of the one or more scan groups includes at least two of the plurality of metrology targets to be measured by the metrology tool in a common scan.

4. The metrology system of claim 3, wherein the one or more processors are configured to separate at least some of the plurality of metrology targets designated for inspection using the scan mode into one or more scan groups based on at least one of target densities along a scan direction.

5. The metrology system of claim 1 , wherein the metrology tool is configured to perform scanning mode measurements by: exposing the sample using illumination from an illumination source during an exposure window; synchronizing the TDI sensor with movement of the sample during the exposure window; and An image is generated line by line during the movement of the sample.

6. The metrology system of claim 5, wherein the metrology tool is configured to perform static mode measurements by: exposing the sample using the illumination from the illumination source while the sample is static during the exposure window without clocking the TDI sensor to transfer charge; and The TDI sensor is clocked to transfer charge row by row to produce an image when the sample is not exposed to the illumination from the illumination source.

7. The metrology system of claim 5, wherein the metrology tool further comprises an imaging detector; The metrology tool is configured to perform static mode measurements by: exposing the sample using the illumination from the illumination source while the sample is static during the exposure window; and An image of the sample is read out using the imaging detector after the exposure window.

8. The metrology system of claim 1, wherein the one or more optical devices include: An array of slits is positioned to block rows of pixels of the TDI sensor that are not illuminated by the cylindrical lens array.

9. The metrology system of claim 1 , wherein the one or more optical devices comprise: an array of slits positioned to pass light to every Nth pixel row of the TDI sensor and block the remaining pixel rows of the TDI sensor, wherein the metrology tool is configured to perform scan mode measurements by: translating the sample along a scan direction perpendicular to the row of pixels at a charge transfer rate of the TDI sensor; sequentially providing the N optical configurations for imaging the sample, 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 comprising the N images during the exposure window using the TDI sensor; and The interlaced image is separated into the N images.

10. The metering system of claim 1, wherein the TDI sensor further comprises: A multi-tap imaging sensor for static mode measurement, the multi-tap imaging sensor having two or more taps, wherein the metrology tool is configured to perform static mode measurement by: sequentially providing the N optical configurations for imaging the sample when the sample is static, wherein the multi-tap imaging sensor is synchronized with the multi-channel illumination source such that a different one of the two or more taps receives a charge for each of the N optical configurations during the exposure window; and The N images are read out from the multi-tap imaging sensor during a readout phase.

11. A measurement method, comprising: receiving, using one or more processors, positions of a plurality of metrology targets on a sample to be inspected; specifying, using one or more processors, the plurality of metrology targets for inspection using a static mode in which the one or more metrology targets on the sample are stationary during measurement or a scanning mode in which the one or more metrology targets are in motion during measurement; performing metrology measurements on the plurality of metrology targets in the static mode or the scanning mode based on the specified guiding of a metrology tool via one or more drive signals using one or more processors, wherein the metrology tool comprises a TDI sensor including a plurality of pixel rows and a multi-channel imaging subsystem, wherein a sample stage is configured to translate the sample in a scanning direction perpendicular to the pixel rows at a charge transfer rate of the TDI sensor, wherein a switching time between consecutive N optical configurations of the multi-channel imaging subsystem corresponds to the charge transfer rate of the TDI sensor; and Metrology data for the sample is generated based on the metrology measurements of the plurality of metrology targets using one or more processors.

12. A metering system comprising: A multi-channel imaging subsystem comprising: Illumination source; one or more illumination optics configured to direct illumination from the illumination source to a sample; one or more light collection optics configured to collect light emitted from the sample in response to the illumination from the illumination source; and a detector configured to generate two or more images of the sample during an exposure window, wherein the detector comprises a TDI sensor including a plurality of rows of pixels, wherein a sample stage is configured to translate the sample in a scanning direction perpendicular to the rows of pixels at a charge transfer rate of the TDI sensor, wherein a switching time between consecutive N optical configurations of the multi-channel imaging subsystem corresponds to the charge transfer rate of the TDI sensor; and a controller communicatively coupled to the detector, the controller comprising one or more processors configured to execute program instructions, the program instructions causing the one or more processors to: generating one or more drive signals for at least one of the illumination source, the one or more illumination optics, the one or more collection optics, or the detector to sequentially cycle through N optical configurations of the multi-channel imaging subsystem within the exposure window of the detector, wherein N is an integer greater than 1, wherein the detector generates N images of the sample during a readout phase associated with the exposure window, wherein a particular image of the N images corresponds to a particular optical configuration of the N optical configurations; and Metrology data associated with the sample is generated based on the N images of the sample.

13. The metrology system of claim 12, wherein the one or more light collection optics comprise: A cylindrical lens array is configured to direct light emitted from the sample to every Nth pixel row of the TDI sensor, wherein the TDI sensor generates an interleaved image containing the N images during the readout phase associated with the exposure window.

14. The metrology system of claim 13, wherein the one or more light collection optics comprise: An array of slits is positioned to block rows of pixels of the TDI sensor that are not illuminated by the cylindrical lens array.

15. The metrology system of claim 12, wherein the one or more light collection optics comprise: A slit array is positioned to pass light to every Nth pixel row of the TDI sensor and block the remaining pixel rows of the TDI sensor, wherein the TDI sensor generates an interleaved image containing the N images during the readout phase associated with the exposure window.

16. The metrology system of claim 15, wherein the array of slots is positioned on the TDI sensor.

17. The metrology system of claim 15, wherein the array of slits is positioned in a field plane of the metrology system.

18. The metering system of claim 12, wherein the detector comprises: a multi-tap imaging sensor having two or more taps adapted to produce at least N images in the exposure window, wherein the multi-tap imaging sensor is synchronized with the multi-channel illumination source such that the multi-tap imaging sensor produces a separate image associated with each of the N optical configurations during the exposure window.

19. The metrology system of claim 12, wherein a particular optical configuration among the N optical configurations comprises: Lighting spectrum.

20. The metrology system of claim 19, wherein the multi-channel illumination source comprises: Broadband light source; and At least one spectral filter.

21. The metrology system of claim 20, wherein the at least one spectral filter is tunable.

22. The metrology system of claim 19, wherein the multi-channel illumination source comprises: Two or more illumination sources having different spectra.

23. The metrology system of claim 12, wherein the multi-channel illumination source comprises at least one spectral filter, wherein a particular optical configuration among the N optical configurations comprises: Lighting spectrum.

24. The metrology system of claim 12, wherein the multi-channel illumination source comprises at least one polarizer, wherein a particular optical configuration of the N optical configurations comprises: Polarized lighting.

25. The metrology system of claim 12, wherein the multi-channel illumination source comprises a variable lens, wherein a particular optical configuration of the N configurations comprises: The position of the imaging plane relative to the surface of the sample.

26. The metrology system of claim 25, wherein the variable lens comprises: At least one of a zoom lens or a translation stage configured to adjust the position of the lens.

27. The metrology system of claim 12, wherein the multi-channel illumination source comprises: Two or more channels having different optical pathways, wherein each of the two or more channels includes one or more optical components for providing illumination having a particular optical configuration of the N optical configurations.

28. The metrology system of claim 27, wherein the multi-channel illumination source further comprises: a beam combiner that routes illumination in each of the two or more channels to a single common optical column, wherein the two or more channels have different optical paths prior to entering the single common optical column; and One or more shutters for selectively blocking illumination in at least one of the two or more channels from reaching the common optical column.

29. The metering system of claim 28, wherein the one or more shutters include: At least one of a mechanical shutter, an electro-optical shutter, or an acousto-optical shutter.

30. The metrology system of claim 12, wherein a particular optical configuration among the N optical configurations comprises: The imaging configuration of the detector.

31. The metrology system of claim 30, wherein the imaging configuration of the detector comprises: At least one of gain or exposure time.

Images