Metrology target for scanning metrology

Abstract

To provide a system and a method for metrology with high throughput.SOLUTION: A metrology system 100 includes a controller 116 coupled to a scanning metrology tool that images a sample 102 in motion along a scan direction. The controller 116 receives an image of a metrology target on the sample 102 from the scanning metrology tool, and the metrology target includes a first measurement group including cells distributed along a transverse direction orthogonal to the scan direction, and a second measurement group separated from the first measurement group along the scan direction and including cells distributed along the transverse direction. The controller 116 further generates at least a first metrology measurement on the basis of at least one of a first set of cells in the first metrology group, and generates at least a second metrology measurement on the basis of at least one of a first set of cells in the second metrology group.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates generally to overlay metrology, and more particularly to targets suitable for scanning overlay metrology systems. [Background technology]

[0002] This application claims the benefit under §119(e) of U.S. Provisional Application No. 62 / 867,142, entitled Scan Overlay (OVL) Target, filed on June 26, 2019, in the names of Andy Hill, Amnon Manassen, Gilad Laredo, Yoel Feler, Mark Ghinovker and Vladimir Levinski as inventors, which is incorporated herein by reference in its entirety.

[0003] Metrology systems typically provide on-product metrology by analyzing dedicated metrology targets, where the characteristics of the manufactured pattern elements exhibit one or more metrology metrics of interest. Shrinking design rules and increasing specification demands for on-product metrology, such as but not limited to overlay-on-product (OPO) metrology, are driving increased sampling requirements at multiple levels of the semiconductor manufacturing process. This increased sampling may further enable greater complexity in overlay models and more precise corrections for lithography systems in response to metrology data. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2017 / 0090302 Summary of the Invention [Problem to be solved by the invention]

[0005] However, increased sampling requirements can have a negative impact on metrology throughput. It would therefore be desirable to provide systems and methods for high throughput metrology. [Means for solving the problem]

[0006] A metrology system is disclosed according to one or more exemplary embodiments of the present disclosure. In one exemplary embodiment, the system includes a controller coupled to a scanning metrology tool, the scanning metrology tool images a sample moving along a scan direction. In another exemplary embodiment, the controller receives an image of a metrology target on the sample from the scanning metrology tool. In another exemplary embodiment, the metrology target includes a first measurement group including one or more cells distributed along a lateral direction on the sample, the lateral direction on the sample being perpendicular to the scan direction. In another exemplary embodiment, the metrology target further includes a second measurement group including one or more cells distributed along a lateral direction on the sample, the second measurement group being separated from the first measurement group along the scan direction. In another exemplary embodiment, the controller generates at least a first metrology measurement based on at least one of the first set of cells in the first metrology group. In another exemplary embodiment, the controller generates at least a second metrology measurement based on at least one of the second set of cells in the second metrology group.

[0007] A metrology system is disclosed according to one or more exemplary embodiments of the present disclosure. In one exemplary embodiment, the system includes a scanning metrology tool for imaging a sample moving along a scan direction. In another exemplary embodiment, the system includes a controller coupled to the scanning metrology tool. In another exemplary embodiment, the controller receives an image of a metrology target on the sample from the scanning metrology tool. In another exemplary embodiment, the metrology target includes a first measurement group including one or more cells distributed along a lateral direction on the sample, the lateral direction on the sample being perpendicular to the scan direction. In another exemplary embodiment, the metrology target further includes a second measurement group including one or more cells distributed along a lateral direction on the sample, the second measurement group being separated from the first measurement group along the scan direction. In another exemplary embodiment, the controller generates at least a first metrology measurement based on at least one of the first set of cells in the first metrology group. In another illustrative embodiment, the controller generates at least a second metrology measurement based on at least one of the second set of cells in the second metrology group.

[0008] A metrology target is disclosed according to one or more exemplary embodiments of the present disclosure. In one exemplary embodiment, the target includes a first measurement group including one or more cells distributed along a lateral direction on the sample, the lateral direction on the sample being perpendicular to the scanning direction. In another exemplary embodiment, one or more cells in the first measurement group can be simultaneously measured by a scanning metrology tool and can further provide at least a first metrology measurement when measured using the scanning metrology tool. In another exemplary embodiment, the target includes a second measurement group including one or more cells distributed along a lateral direction on the sample, the second measurement group being separated from the first measurement group along the scanning direction. In another exemplary embodiment, one or more cells in the second measurement group can be simultaneously measured by a scanning metrology tool and can further provide at least a second metrology measurement when measured using the scanning metrology tool.

[0009] It is to 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.

[0010] Many advantages of the present disclosure can be better understood by those skilled in the art by reference to the following drawings. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram illustrating a scanning metrology system in accordance with one or more embodiments of the present disclosure. [Diagram 2] FIG. 2 is a top view of a static metrology target suitable for static mode metrology measurements where the sample is stationary during the measurement, in accordance with one or more embodiments of the present disclosure. [Diagram 3] FIG. 1 is a conceptual diagram of a scanning metrology target in accordance with one or more embodiments of the present disclosure. [Figure 4A] FIG. 1 is a top view of a scanning metrology target having two measurement groups for overlay metrology along orthogonal directions, where cells within each of the two measurement groups exhibit rotational symmetry, in accordance with one or more embodiments of the present disclosure. [Figure 4B] FIG. 1 is a top view of a scanning metrology target having two measurement groups for overlay metrology along orthogonal directions, where cells within each of the two measurement groups exhibit rotational symmetry, in accordance with one or more embodiments of the present disclosure. [Figure 4C] FIG. 2 is a top view of a scanning metrology target having a number of identical cells in accordance with one or more embodiments of the present disclosure. [Figure 4D] FIG. 1 is a top view of a scanning metrology target having two measurement groups, in which cells within each measurement group exhibit reflection symmetry, in accordance with one or more embodiments of the present disclosure. [Diagram 5]FIG. 13 is a top view of a scanning metrology target having two cell groups with three cells each for overlay metrology along orthogonal directions in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Reference will now be made in detail to the disclosed subject matter, as illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with reference to certain embodiments and certain features thereof. The embodiments shown herein should be construed as illustrative and not limiting. It should be readily apparent to those skilled in the art that various changes and modifications in form and detail can be made without departing from the spirit and scope of the present disclosure.

[0013] Embodiments of the present disclosure are directed to systems and methods for scan-based metrology in which a metrology target is characterized by a metrology tool while being translated through a focal volume of the metrology tool.

[0014] A metrology target can typically include well-defined printed elements designed to provide an accurate representation of one or more printing characteristics. In this regard, the measured (e.g., by a metrology tool) characteristics of the printed elements of the metrology target can represent the printed device elements associated with the device being manufactured. Furthermore, a metrology target is typically characterized as having one or more measurement cells, each cell including printed elements in one or more layers on a sample. In this case, the metrology measurement can be based on any combination of measurements of the size, orientation, or location (e.g., pattern placement) of the printed elements within a single cell or among multiple cells.

[0015] For example, one or more cells of an overlay metrology target may include printed elements on two or more sample layers arranged such that the relative position of the elements of each layer may indicate an offset error of a particular layer (e.g., pattern placement errors (PPE)), or an overlay error associated with a positioning error between the sample layers. As another example, a process sensitive metrology target may include printed elements on a single sample layer, where one or more characteristics of the printed elements (e.g., width or critical dimension (CD), sidewall angle, position, etc.) indicate one or more process metrics, such as, but not limited to, the amount of illumination applied during a lithography step, or the focal position of a sample in a lithography tool during a lithography step.

[0016] A metrology system can inspect a metrology target using a variety of techniques. For example, a metrology system can inspect a metrology target using a move-and-measure (MAM) mode of operation, where a sample is translated to place a metrology target of interest within the measurement field, a measurement is performed while the sample is stationary, and the sample is then translated to place additional metrology targets of interest within the measurement field. As another example, a metrology system can inspect a metrology target while the sample is moving (e.g., in a scanning mode of operation). For example, a scanning metrology tool can continuously analyze a sample while the sample is scanned along a scan direction through a measurement field. Additionally, a scanning metrology tool can effectively inspect multiple adjacent targets distributed along a scan direction in a single scan, which eliminates the time-consuming settling time requirements associated with MAM tools. Scanning metrology tools are generally described in U.S. patent application Ser. No. 15 / 761,830, filed Mar. 21, 2018, which is incorporated herein by reference.

[0017] Embodiments of the present disclosure are directed to metrology targets suitable for inspection using a scanning mode of operation. It is recognized herein that scanning metrology tools have different error sources than MAM metrology tools due to the different modes of operation. In particular, while MAM metrology tools can capture images of one or more cells in a single frame, scanning metrology tools typically generate images line by line while the sample is being scanned. Thus, scanning metrology tools may be sensitive to time-varying errors such as, but not limited to, vibration errors or jitter errors that affect different portions of the image to different degrees.

[0018] Thus, a scanning metrology target (as well as a system for measuring such a target) designed according to the present disclosure includes one or more measurement groups, which include one or more cells designed for a common metrology measurement distributed along a direction perpendicular to the scanning direction of the sample. In this regard, the cells in each measurement group are inspected simultaneously to mitigate the effects of time-varying errors during the measurement. Measurement errors, such as scan velocity errors or scan position errors, are common to all cells in each measurement group, which may facilitate consistent and accurate measurement of the cells in the measurement group.

[0019] Additionally, scanning metrology targets designed according to the present disclosure can include any number of measurement groups distributed along the scan direction. Although time-varying errors may affect cells in one measurement group differently than cells in a different measurement group, these errors may have minimal impact on the metrology measurements because the metrology measurements typically (but not exclusively) encompass cells within a single measurement group.

[0020] A measurement group can include any combination of one or more cells designed to generate any number of metrology measurements. For example, in the context of overlay metrology, a scanning metrology target can include a first measurement group having cells suitable for overlay measurement in a first direction (e.g., X-direction) and a second measurement group having cells suitable for overlay measurement in an orthogonal second direction (e.g., Y-direction). As another example, a scanning metrology target can include cells suitable for overlay measurement in both the first and second directions in a common measurement group.

[0021] Additional embodiments of the present disclosure are directed to a scanning metrology tool suitable for analyzing the scanning metrology target described herein. For example, the scanning metrology tool may continuously analyze the scanning metrology target while the scanning metrology target moves relative to the measurement field, receive metrology signals associated with each of the cells, and generate metrology data from the metrology signals. Additionally, the scanning metrology tool may apply a common measurement algorithm to the cells in each cell group to generate metrology data from the corresponding metrology signals.

[0022] Additional embodiments of the present disclosure are directed to one or more pattern masks suitable for generating a scanning metrology target. For example, the pattern mask can include pattern elements suitable for being imaged in a lithography system onto a sample for fabricating a scanning metrology target. In particular, the pattern mask can include pattern elements in one or more cells of one or more groups of cells associated with a particular layer to be fabricated on the sample. Furthermore, multiple pattern masks can include pattern elements for fabrication onto multiple sample layers for fabricating a multi-layer scanning metrology target (e.g., a scanning overlay target, etc.).

[0023] A system and method for metrology using a scanning metrology target will now be described in more detail with reference to FIGS.

[0024] 1 is a block diagram illustrating a scanning metrology system 100 in accordance with one or more embodiments of the present disclosure. The scanning metrology system 100 may include various components for analyzing a sample 102, or a portion thereof, while the sample 102 is scanned relative to a measurement field. For example, the scanning metrology system 100 may be configured to analyze a scanning metrology target on the sample 102 while the sample 102 is scanned, which is described in more detail below.

[0025] In one embodiment, the scanning metrology system 100 includes an illumination source 104 configured to generate an illumination beam 106. In another embodiment, the scanning metrology system 100 includes an illumination path 108 including one or more components for directing the illumination beam 106 onto the sample 102. In another embodiment, the scanning metrology system 100 includes a collection path 110 including one or more components for collecting the sample radiation 112. In another embodiment, the scanning metrology system 100 includes a detector 114 configured to capture at least a portion of the sample radiation 112 from the collection path 110. In another embodiment, the scanning metrology system 100 includes a scanning subsystem (e.g., one or more translation stages, beam scanners, etc.) configured to condition the sample 102 and / or the illumination beam 106 prior to, during, and / or after a measurement.

[0026] In another embodiment, the scanning metrology system 100 includes a controller 116. In another embodiment, the controller 116 includes one or more processors 118. In another embodiment, the one or more processors 118 are configured to execute a set of program instructions held in a memory medium 120, i.e., a memory. Additionally, the controller 116 may include one or more modules that include one or more program instructions stored in the memory medium 120 and executable by the processor 118. The processor 118 of the controller 116 may include any processing element known in the art. In this sense, the processor 118 may include any microprocessor-based device configured to execute algorithms and / or instructions. In an embodiment, the processor 118 may comprise a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, or any other computer system (e.g., a networked computer) configured to execute programs configured to operate the scanning metrology system 100 described throughout this disclosure. It is 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 a non-transitory memory medium 120.

[0027] The memory medium 120 may include any storage medium known in the art suitable for storing program instructions executable by an associated processor 118. For example, the memory medium 120 may include a non-transitory memory medium. As an additional example, the memory medium 120 may include, but is not limited to, a read-only memory, a random access memory, a magnetic or optical memory device (e.g., a disk), a magnetic tape, a solid state drive, and the like. It is further noted that the memory medium 120 may be housed in a common controller housing with the processor 118. In one embodiment, the memory medium 120 may be located remotely relative to the physical location of the processor 118 and the controller 116. For example, the processor 118 of the controller 116 may access a remote memory (e.g., a server) that may be accessible via a network (e.g., the Internet, an intranet, and the like). Thus, the above description should not be construed as a limitation on the present invention, and the above description is merely illustrative.

[0028] The controller 116 may be communicatively coupled to any component of the scanning metrology system 100. In one embodiment, the controller 116 receives data from one or more components of the scanning metrology system 100. For example, the controller 116 may receive metrology signals (e.g., one or more images, etc.) associated with the scanning metrology target from the detector 114. In another embodiment, the controller 116 performs one or more processing steps of the present disclosure. As another example, the controller 116 may receive position feedback from the sample stage 134 indicating a position, a velocity, or other relevant parameters. In another embodiment, the controller 116 analyzes or otherwise processes the metrology signals from the detector 114. For example, the controller 116 may generate metrology data based on metrology signals from the scanning metrology target, such as, but not limited to, overlay data, a focus position of the sample 102 during one or more lithography steps, or illumination application dose during one or more lithography steps. In another embodiment, the controller 116 may generate one or more control signals to direct or otherwise control components of the scanning metrology system 100. The controller 116 may generate control signals to any component of the scanning metrology system 100, including, but not limited to, the detector 114, the sample stage 134, the illumination source 104, or any component of the illumination path 108 or the collection path 110.

[0029] Additionally, the scanning metrology system 100 may operate as any type of metrology system known in the art. In one embodiment, the scanning metrology system 100 is an imaging metrology system and may generate metrology data based on one or more images of the sample 102. In another embodiment, the scanning metrology system 100 is a scatterometry metrology system and the metrology data is based on one or more pupil images associated with the diffraction and / or scattering of the illumination beam 106 by the sample 102.

[0030] With further reference to FIG. 1, the various components of the scanning metrology system 100 will now be described in more detail.

[0031] The illumination source 104 may include any type of light source known in the art. Additionally, the illumination source 104 may have any selected spectral content.

[0032] In one embodiment, the illumination source 104 includes one or more coherent sources, such as, but not limited to, one or more laser sources. In this regard, the illumination source 104 can provide an illumination beam 106 with high coherence (e.g., high spatial coherence and / or temporal coherence). For example, the illumination source 104 can include one or more broadband lasers, such as, but not limited to, one or more supercontinuum lasers or white light lasers. As another example, the illumination source 104 can include one or more narrowband lasers. As yet another example, the illumination source 104 can include one or more tunable lasers for providing an illumination beam 106 with a tunable spectral intensity. Furthermore, the coherent illumination source 104 can be based on any type of technology or product design. For example, the illumination source 104 can include any combination of, but not limited to, one or more fiber lasers, one or more diode lasers, or one or more gas lasers.

[0033] In another embodiment, illumination source 104 includes one or more low coherence sources for providing illumination beam 106 having low or partial coherence (e.g., spatial and / or temporal coherence). For example, illumination source 104 can include one or more light emitting diodes (LEDs). As another example, illumination source 104 can include a laser-sustained plasma (LSP) source, such as, but not limited to, an LSP lamp, an LSP bulb, or an LSP chamber adapted to include one or more elements capable of emitting broadband illumination when excited into a plasma state by a laser source. As another example, illumination source 104 can include a lamp source, such as, but not limited to, an arc lamp, a discharge lamp, an electrodeless lamp, and the like.

[0034] Additionally, illumination source 104 may include any combination of light sources. In one embodiment, illumination source 104 includes one or more supercontinuum laser sources to provide broadband illumination, and one or more partially coherent high brightness LEDs to supplement gaps in the spectra of the one or more supercontinuum laser sources.

[0035] The illumination source 104 can further provide light having any selected temporal characteristics. In one embodiment, the illumination source 104 includes one or more continuous wave sources for providing a continuous wave illumination beam 106. In another embodiment, the illumination source 104 includes one or more pulsed sources for providing a pulsed or otherwise modulated illumination beam 106. For example, the illumination source 104 can include one or more mode-locked lasers, one or more Q-switched lasers, or the like.

[0036] In one embodiment, the illumination path 108 includes one or more lenses 122. In another embodiment, the illumination path 108 includes one or more optical components 124 suitable for modifying and / or conditioning the illumination beam 106. For example, the one or more optical components 124 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, or one or more beam shapers.

[0037] In another embodiment, the scanning metrology system 100 includes an objective lens 126 for focusing the illumination beam 106 onto the sample 102 .

[0038] The sample radiation 112 may include any type of radiation, including but not limited to light or particles, emitted by the sample 102. For example, the sample radiation 112 may include a portion of the illumination beam 106 that is reflected and / or scattered by the sample 102. As another example, the sample radiation 112 may include luminescence induced by absorption of the illumination beam 106 by the sample 102. As another example, the sample radiation 112 may include particles, such as but not limited to backscattered electrons or secondary electrons from the sample 102 in response to the illumination beam 106.

[0039] In one embodiment, the collection path 110 includes one or more lenses 128. In another embodiment, the collection path 110 includes one or more optical components 130 suitable for modifying and / or conditioning the illumination beam 106. For example, the one or more optical components 130 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 apodizers, or one or more beam shapers.

[0040] In another embodiment, the scanning metrology system 100 includes a beam splitter 132. For example, as shown in FIG. 1 , the beam splitter 132 may be common to both the illumination path 108 and the collection path 110 such that the objective lens 126 can both direct the illumination beam 106 to the sample 102 and collect the sample radiation 112. In another embodiment, not shown, the illumination path 108 and the collection path 110 can each include separate lenses for directing the illumination beam 106 to the sample 102 and collecting the sample radiation 112.

[0041] The detector 114 may include any photodetector known in the art suitable for capturing sample radiation 112 received from the sample 102. In one embodiment, the detector 114 includes a multi-pixel detector suitable for capturing one or more images. For example, the detector 114 may include, but is not limited to, a charge-coupled device (CCD), a complementary metal-oxide semiconductor (CMOS) device. The detector 114 may be positioned at any imaging plane of the scanning metrology system 100. For example, the detector 114 may be positioned at a conjugate plane with respect to the sample 102 to generate an image of the sample 102. In another example, the detector 114 may be positioned at a pupil plane (or a conjugate thereof) to generate a pupil image.

[0042] Additionally, the scanning metrology system 100 may include multiple detectors 114 (e.g., associated with multiple beam paths generated by one or more beam splitters to facilitate multiple metrology measurements (e.g., multiple metrology tools) by the scanning metrology system 100). In another embodiment, the detector 114 may include a spectroscopic detector suitable for identifying wavelengths of radiation emitted by the sample 102.

[0043] In another embodiment, the scanning metrology system 100 includes a scanning subsystem for scanning the sample 102 relative to the measurement field during metrology measurements. In one embodiment, as shown in FIG. 1, the scanning subsystem includes a sample stage 134 for securing and / or positioning the sample 102 within the measurement field of the scanning metrology system 100. For example, the sample stage 134 can position and orient the sample 102 within the focal volume of the objective lens 126. In another embodiment, the sample stage 134 includes one or more adjustable stages, such as, but not limited to, a linear translation stage, a rotational stage, or a tip / tilt stage. In another embodiment, not shown, the scanning subsystem includes one or more beam scanning optics (e.g., rotatable mirrors, galvanometers, etc.) for scanning the illumination beam 106 relative to the sample 102.

[0044] The detector 114 can be configured to generate metrology signals (e.g., sample plane image and / or pupil plane image) during scanning using any technique known in the art. In one embodiment, the detector 114 includes a 2D pixel array with sufficient capture time and / or refresh rate to capture one or more images during scanning within a selected image likelihood (e.g., image blur, contrast, sharpness, etc.). In another embodiment, the detector 114 includes a line-scan detector for sequentially generating images of one line of pixels at a time. In another embodiment, the detector 114 includes a time-delay integration (TDI) detector. The TDI detector can generate sequential images of the sample 102 when the movement of the sample 102 is synchronized to a charge transfer clock signal in the TDI detector. In particular, the TDI detector acquires charge from exposure to a row of pixels and includes a clock pulse for transferring charge between adjacent rows of pixels along the scan direction. If the movement of the sample 102 along the scan direction is synchronized with the charge transfer in the TDI detector, charge accumulates continuously during the scan. This process continues until the charge reaches the last row of pixels and is then read out from the detector. In this way, an image of the object is accumulated over a longer time frame than would be possible using a single line scan camera. This relatively longer acquisition time results in a lower photon noise level in the image. Furthermore, the synchronized movement of the image and the charge prevents blurring in the recorded image.

[0045] 2-4, various metrology target designs will now be described in more detail.

[0046] FIG. 2 is a top view of a static metrology target 202 suitable for static mode (eg, frame mode) metrology measurements in which the sample 102 remains stationary during the measurements, in accordance with one or more embodiments of the present disclosure.

[0047] 2 may be suitable for overlay metrology to determine a positioning error between two layers of the sample 102. In particular, the static metrology target 202 may include four cells 204a-d, represented here as quadrants of the static metrology target 202. Each cell 204a-d may include a first layer print element 206 disposed on a first layer of the sample 102 and a second layer print element 208 disposed on a second layer of the sample 102.

[0048] Further, the cells 204a and 204d can be configured to provide overlay measurements along the X direction shown in FIG. 2. For example, overlay measurements along the X direction can be performed by directly comparing the relative positions of the first layer print element 206 and the second layer print element 208 within each cell or between the cells 204a and 204d. In another example, overlay measurements along the X direction can be performed by comparing rotationally symmetric points (e.g., rotationally symmetric, reflectively symmetric, mirror symmetric, etc.) between the first layer print elements 206 distributed across the cells 204a and 204d and symmetric points between the second layer print elements 208 distributed across the cells 204a and 204d. Similarly, the cells 204b and 204c can be configured to provide overlay measurements along the Y direction shown in FIG. 2.

[0049] It is recognized herein that a metrology tool configured for static measurements (e.g., MAM mode of operation) may capture an image of the static metrology target 202 in a single measurement field of view 210 (e.g., a single frame). Thus, the impact of time-varying errors of the metrology tool on the metrology measurements may be generally limited to the impact of time-varying errors occurring over a time frame on the order of the exposure time required to generate all images of the static metrology target 202. Furthermore, because all of the cells 204a-d are imaged simultaneously in a single image, the time-varying errors will all have a common impact on various portions of the image. In this regard, the time-varying errors may not typically introduce a difference between the portion of the image associated with cell 204a (or cell 204b) and the portion of the image associated with cell 204d (or cell 204c).

[0050] However, it is further recognized herein that a scanning metrology system 100 configured for scanning measurements may generate an image of the static metrology target 202 line-by-line while the sample 102 is translated through the measurement field. Thus, time-varying errors may introduce differences between the portion of the image associated with cell 204a (or cell 204b) and the portion of the image associated with cell 204d (or cell 204c) that may directly affect overlay metrology measurements.

[0051] 3-5, a metrology target suitable for scanning mode measurements will be described in accordance with one or more embodiments of the present disclosure.

[0052] FIG. 3 is a conceptual diagram of a scanning metrology target 302 in accordance with one or more embodiments of the present disclosure.

[0053] In one embodiment, the scanning metrology target 302 includes a plurality of measurement cells 304 distributed over the sample 102, with each cell 304 including a printed element designed to provide a selected metrology measurement on one or more layers of the sample 102. For example, overlay metrology measurements can utilize the relative positions between pattern elements on two or more layers of the sample 102 during lithography to determine the positioning error of the associated layers, where the pattern elements are disposed within one or more cells 304 of the scanning metrology target 302. As another example, the cells 304 can include printed elements on one or more sample layers, where characteristics such as, but not limited to, size, critical dimension (CD) or position are indicative of one or more process parameters during exposure (e.g., focus position of the sample 102, illumination dosage, etc.).

[0054] In another embodiment, the cells 304 in the scanning metrology target 302 are organized into one or more measurement groups 306 that are distributed along a scan direction 308 (e.g., the direction in which the sample 102 is scanned during a measurement). For example, each measurement group 306 can include any number of cells 304 that are distributed along a lateral direction 310 perpendicular to the scan direction 308, and the scanning metrology target 302 can include any number of measurement groups 306 along the scan direction 308.

[0055] It is recognized herein that the scanning metrology system 100 may have multiple associated error sources that may negatively impact metrology performance. In particular, because the scanning metrology system 100 generates successive images along the scan, the effects of time-varying errors, such as, but not limited to, vibration or jitter, may manifest as changes in certain portions of the successive images relative to other portions (e.g., spatial changes within the successive images). For example, errors associated with the scan direction 308 may induce a lateral shift in certain portions of the successive images along the lateral direction. As another example, errors associated with the translational velocity (e.g., scan rate) along the scan direction 308 may manifest as stretching or shrinking of portions of the successive images.

[0056] In the context of metrology, spatial variations in successive images due to system-induced errors can negatively affect the performance of metrology algorithms designed to extract information about the sample from the images. For example, overlay metrology can measure positioning errors between sample layers based on the relative positions of imaged features on two or more layers of the sample 102. However, spatial variations in the images can sometimes directly affect the location of features in the images and therefore directly contribute to measurement errors. As another example, critical dimension metrology can measure the size of features on a sample based on the size of the features in the images. However, spatial variations in the images can sometimes directly affect the imaged size of features at different locations along the scan direction 308 and therefore directly contribute to inconsistent measurement results along the scan direction 308.

[0057] Thus, in an embodiment of the present disclosure, cells 304 associated with a common metrology measurement may be arranged to be placed in a common measurement group 306. In this regard, the cells 304 in each measurement group 306 may be measured simultaneously to mitigate the effects of time-varying errors. It is recognized herein that time-varying errors may still affect the cells 304 in each measurement group 306. However, only time-varying errors occur on a time scale of the order of the measurement time of the measurement group 306 (e.g., approximately the size of the largest cell 304 measured along the scan direction 308). Moreover, even those errors that occur on this time scale will affect all cells 304 in the measurement group 306 in the same way.

[0058] However, it should be understood that the metrology algorithm does not preclude the use of cells 304 in different measurement sets 306. It is merely contemplated herein that increasing the size of the portion of the image along the scan direction 308 that is analyzed may increase the effect of time-varying errors.

[0059] The scanning metrology target 302 can include any selected number of measurement groups 306, with each measurement group 306 including any number of cells 304 suitable for any selected metrology measurement. In one embodiment, the scanning metrology target 302 can include a first measurement group 306 having one or more cells 304 designed to provide an overlay measurement along a first direction (e.g., X-direction) and a second measurement group 306 having one or more cells 304 designed to provide an overlay measurement along a second direction (e.g., Y-direction). In this regard, the cells 304 in the first measurement group 306 associated with overlay metrology along the first direction can be measured simultaneously to provide accurate metrology data. Similarly, the cells 304 in the second measurement group 306 associated with overlay metrology along the first direction can also be measured simultaneously. In another embodiment, the scanning metrology target 302 can include one or more cells 304 in a common measurement group 306 designed to provide overlay measurements along multiple directions (e.g., X-direction and Y-direction). In this regard, cells 304 in a common measurement group 306 associated with overlay metrology along multiple directions can be measured simultaneously. In another embodiment, the scanning metrology target 302 can include one or more cells 304 in a common measurement group 306 designed to provide CD metrology, thereby minimizing or otherwise mitigating the effects of time-varying errors on CD measurements for features at different locations in the scanning metrology target 302. In another embodiment, the scanning metrology target 302 can include one or more cells 304 in a common measurement group 306 designed to provide process metrology data (e.g., illumination dosage, focus position in a lithography tool, etc.), thereby minimizing or otherwise mitigating the effects of time-varying errors on process metrology measurements. It should therefore be understood that examples of providing a particular number or layout of measurement groups 306 in the scanning metrology target 302 are provided by way of illustration only and should not be construed as limiting.

[0060] In one embodiment, the scanning metrology target 302 includes one or more measurement groups 306, with various measurement groups 306 within each measurement group 306 providing metrology measurements (e.g., overlay, process monitoring, etc.) associated with a common direction on the sample 102. For example, the scanning metrology target 302 may include a first measurement group 306 that may include cells 304 that provide metrology measurements along a first direction, and a second measurement group 306 that may include cells 304 that provide metrology measurements along a second direction different from the first direction. The first direction and the second direction may be, but need not be, orthogonal. Additionally, the first direction and the second direction may correspond to a scanning direction 308 and a lateral direction 310, but need not be.

[0061] Thus, the measurement group 306 can include cells 304 having printed elements having any selected pattern suitable for providing a selected metrology measurement of interest. In one embodiment, the measurement group 306 includes at least one cell 304 having a periodic printed element. For example, the periodic printed element can include multiple (e.g., three or more) elements having a common spacing along a selected direction. Additionally, the multiple elements can have a common dimension, although this is not necessarily the case.

[0062] 4A-5, various configurations of the scanning metrology target 302 are described in accordance with one or more embodiments of the present disclosure. For example, it is contemplated herein that the overlay can be designed to provide an overlay measurement based on any measurement algorithm known in the art. For example, an overlay measurement along a measurement direction can be generated by directly comparing the relative positions or points of symmetry (e.g., rotational symmetry, reflection symmetry, etc.) of print elements generated using different exposure steps. Furthermore, although the configurations of the scanning metrology target 302 shown in FIG. 4A-5 are designed for overlay metrology, it should be understood that the scanning metrology target 302 configured in accordance with the present disclosure is not limited to overlay metrology. Thus, it is contemplated herein that one skilled in the art can extend the features and operating principles described in the embodiments illustrated herein to additional metrology target designs.

[0063] FIG. 4A is a top view of a scanning metrology target 302 having two measurement groups 306a, b for overlay metrology along orthogonal directions, in which the cells 304 within each of the two measurement groups 306a, b exhibit rotational symmetry, in accordance with one or more embodiments of the present disclosure.

[0064] In one embodiment, the scanning metrology target 302 includes a first measurement group 306a including a first cell 304a and a second cell 304b distributed along the lateral direction 310, and a second measurement group 306b including a third cell 304c and a fourth cell 304d distributed along the lateral direction 310. The second measurement group 306b is separated from the first measurement group 306 along the scanning direction 308. Additionally, the cells 304a-d are depicted as having a first set of printed elements 402 and a second set of printed elements 404. The first set of printed elements 402 and the second set of printed elements 404 can be printed using different process steps. For example, the first set of printed elements 402 can be fabricated on a first layer of the sample 102, and the second set of printed elements 404 can be fabricated on a second layer of the sample. As another example, the first set of printed elements 402 and the second set of printed elements 404 can be fabricated on a common layer of the sample 102 in different processing steps.

[0065] Additionally, any of cells 304a-d may include cells 304 having printed elements having any selected pattern suitable for providing a selected metrology measurement of interest. For example, measurement group 306a and / or measurement group 306b may include at least one cell 304 having periodic printed elements. For example, the periodic printed elements may include multiple (e.g., three or more) elements having a common spacing along a selected direction. Additionally, the multiple elements may, but need not, have a common dimension.

[0066] In one embodiment, the first cell 304a and the second cell 304b in the first measurement group 306a are configured to provide overlay measurements along a first direction (e.g., X-direction), while the third cell 304c and the fourth cell 304d in the second measurement group 306b are configured to provide overlay measurements along a second direction (e.g., Y-direction). In this regard, the first cell 304a and the second cell 304b in the first measurement group 306a can be imaged simultaneously to minimize or otherwise mitigate the effects of time-varying errors on associated metrology measurements along the first direction. Similarly, the third cell 304c and the fourth cell 304d in the second measurement group 306b can also be imaged simultaneously to minimize or otherwise mitigate the effects of time-varying errors on associated metrology measurements along the second direction.

[0067] Additionally, the scanning metrology target 302 of FIG. 4A may be well suited for overlay metrology based on, but not limited to, the rotational symmetry of the cells 304. For example, the cell 304b may be designed to correspond to a 180 degree rotation of the cell 304a in the absence of overlay error such that an overlay measurement along the X direction may be generated by comparing the rotationally symmetric point 406 of the first set of printing elements 402 in the measurement group 306a to the rotationally symmetric point 408 of the second set of printing elements 404 in the measurement group 306a. Similarly, in FIG. 4A, the cell 304d may be designed to correspond to a 180 degree rotation of the cell 304c in the absence of overlay error such that an overlay measurement along the Y direction may be generated by comparing the rotationally symmetric point 410 of the first set of printing elements 402 in the measurement group 306b to the rotationally symmetric point 412 of the second set of printing elements 404 in the measurement group 306b. In this regard, measurements of the rotationally symmetric cell 304 can mitigate or otherwise reduce rotational errors of the scanning metrology system 100 .

[0068] It is contemplated herein that various arrangements of elements within a cell 304 of a measurement group 306 can provide the desired symmetry. Figure 4B is a top view of a scanning metrology target 302 having two measurement groups 306a,b for overlay metrology along orthogonal directions, in accordance with one or more embodiments of the present disclosure, where the cells 304 within each of the two measurement groups 306a,b exhibit rotational symmetry. In particular, the cells 304c,d in the measurement group 306b of Figure 4B are distributed along the Y direction (e.g., measurement direction), resulting in an increased length of the measurement group 306b along the Y direction as compared to the scanning metrology target 302 of Figure 4A.

[0069] It is further contemplated herein that the scanning metrology target 302 is suitable for scanning in multiple directions, and a common target may be used to facilitate comparison of measurements obtained along different directions. For example, the scanning metrology target 302 of FIG. 4B may be scanned along the X direction (e.g., the scan direction 308 and lateral direction 310 shown in FIG. 4B may be swapped).

[0070] However, it should be understood that the 180 degree rotational symmetry shown in Figures 4A and 4B is provided merely for illustrative purposes and should not be construed as limiting. Rather, the scanning metrology target 302 (or any group of cells 304 in the measurement group 306) may correspond to versions rotated by any amount (e.g., 45 degrees, 90 degrees, etc.) relative to one another.

[0071] Furthermore, as previously discussed herein, the cells 304 in a measurement group 306 need not have any rotational symmetry.

[0072] In another embodiment, the measurement group 306 includes a plurality of identical cells 304. Figure 4C is a top view of a scanning metrology target 302 having a plurality of identical cells 304c, d, in accordance with one or more embodiments of the present disclosure. Thus, an overlay measurement along the Y direction can be generated by performing overlay measurements on cells 304c and 304d individually (e.g., based on the relative positions and / or points of symmetry of the first set of printed elements 402 and the second set of printed elements 404 in cells 304c and 304d, respectively), and then averaging the individual measurements to offset rotational errors of the scanning metrology system 100.

[0073] In another embodiment, the measurement group 306 includes one or more pairs of cells 304 designed to have reflection symmetry (e.g., mirror symmetry, 1-D symmetry, etc.) along a desired measurement direction (e.g., X-direction, Y-direction, etc.). FIG. 4D is a top view of a scanning metrology target 302 having two measurement groups 306a,b, in which the cells 304 in each of the two measurement groups 306a,b exhibit reflection symmetry, in accordance with one or more embodiments of the present disclosure. For example, the first set of printing elements 402 and the second set of printing elements 404 in the measurement group 306a can be designed to be symmetric about an axis 414 such that an overlay measurement along the X-direction can be associated with a comparison of the axis of symmetry of the first set of printing elements 402 in the measurement group 306a to the axis of symmetry of the second set of printing elements 404 in the measurement group 306a. Similarly, the first set of printing elements 402 and the second set of printing elements 404 in the measurement group 306b can be designed to be symmetrical about axis 416 so that overlay measurements along the Y direction can be associated with a comparison of the axis of symmetry of the first set of printing elements 402 in the measurement group 306b with the axis of symmetry of the second set of printing elements 404 in the measurement group 306b.

[0074] In another embodiment, the measurement group 306 includes a plurality of cells 304 that provide the same metrology measurement but with printed elements having different layouts (e.g., a first set of printed elements 402 and a second set of printed elements 404). For example, the printed elements in a cell 304 may include pitch variations between elements, between segments of elements, between asymmetric elements, etc. In this regard, metrology signals associated with the plurality of cells 304 may be used to monitor process errors and / or pattern placement errors (PPE), where process errors are sensitive to variations in the printed elements.

[0075] In another embodiment, a particular cell 304 may include a pattern element (e.g., a grating, etc.) that has an intentionally inserted skew (e.g., an offset). In this regard, metrology measurements of the cell 304 may be utilized to provide residual minimization by algorithms and / or flags.

[0076] It should be understood, however, that the illustrations of the measurement group 306 having two cells 304 shown in Figures 4A-4D, respectively, are provided for illustrative purposes only and should not be construed as limiting. The measurement group 306 of the scanning metrology target 302 can include any number of cells 304.

[0077] 5 is a top view of a scanning metrology target 302 having two measurement groups 306 with three cells 304, each for overlay metrology along orthogonal directions, in accordance with one or more embodiments of the present disclosure. For example, the scanning metrology target 302 can include a first measurement group 306a having cells 304a-c and a second measurement group 306b having cells 304d-f. Furthermore, as shown in FIG. 5, the symmetry between the cells 304 can be different between different measurement groups 306. For example, the first measurement group 306a includes a cell 304 with two rotational variants, while the second measurement group 306b includes the exact same cell 304.

[0078] The subject matter described herein illustrates different components that are sometimes contained within or connected to other components. It should be understood that such depicted architectures are merely exemplary, and that in fact many other architectures that achieve the same functionality can be realized. In a conceptual sense, components of any structure to achieve the same functionality are effectively "associated" such that the desired functionality is achieved. Thus, in this specification, any two components that are combined to achieve a particular functionality can be considered to be "associated" with each other such that the desired functionality is achieved regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "connected" or "coupled" with each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be "combinable" with each other to achieve the desired functionality. Particular examples of combineable 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.

[0079] The present disclosure and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes in form, construction and arrangement of the components may be made without departing from the disclosed subject matter or sacrificing all of its essential advantages. The described forms are merely illustrative, and the following claims are intended to encompass and include such modifications. It is to be understood, further, that the invention is defined by the appended claims.

Claims

1. A metrology target, a first measurement group including one or more cells distributed along a lateral direction on a sample, the lateral direction on the sample being perpendicular to a scanning direction, the one or more cells in the first measurement group being configured to be simultaneously measured by a scanning metrology tool, and further configured to provide at least a first metrology measurement when measured using the scanning metrology tool; a second measurement group including one or more cells distributed along the lateral direction on the sample, the second measurement group separated from the first measurement group along the scanning direction, the one or more cells in the second measurement group configured to be simultaneously measured by the scanning metrology tool, and further configured to provide at least a second metrology measurement when measured using the scanning metrology tool; A metrology target comprising:

2. 2. The metrology target of claim 1, further comprising one or more additional measurement groups each including one or more cells distributed along the lateral direction on the sample, the one or more additional measurement groups separated from the first measurement group and the second measurement group along the scanning direction, the one or more cells in each additional measurement group of the at least one additional measurement group configured to be measured simultaneously by the scanning metrology tool, and further configured to provide at least an additional metrology measurement value when measured using the scanning metrology tool.

3. 2. The metrology target of claim 1, the first metrology measurements include overlay metrology measurements along a first direction on the sample; The second metrology measurements include overlay metrology measurements along a second direction on the sample that is different from the first direction. A metrology target comprising:

4. 4. The metrology target of claim 3, wherein the overlay measurements along the first direction on the sample are based on relative positions of two or more sets of printing elements in the one or more cells of the first measurement group, and the overlay measurements along the second direction on the sample are based on relative positions of two or more sets of printing elements in the one or more cells of the second measurement group.

5. 4. The metrology target of claim 3, wherein the first measurement group includes two or more cells, and the overlay measurements along the first direction on the sample are based on relative positions of centers of rotational symmetry of two or more sets of printing elements distributed across the two or more cells in the first measurement group, and the second measurement group includes two or more cells, and the overlay measurements along the second direction on the sample are based on relative positions of centers of rotational symmetry of two or more sets of printing elements distributed across the two or more cells in the second measurement group.

6. 4. The metrology target of claim 3, wherein the first measurement group includes two or more cells, and the overlay measurements along the first direction on the sample are based on relative positions of axes of reflective symmetry of two or more sets of printing elements distributed across the two or more cells in the first measurement group, and the second measurement group includes two or more cells, and the overlay measurements along the second direction on the sample are based on relative positions of axes of reflective symmetry of two or more sets of printing elements distributed across the two or more cells in the second measurement group.

7. 2. The metrology target of claim 1, wherein at least one of the first set of cells or the second set of cells includes two or more identical cells.

8. 2. The metrology target of claim 1, wherein at least one of the first measurement group or the second measurement group includes a cell having a set of periodic printed elements.

9. 2. The metrology target of claim 1, wherein at least one of the first metrology measurement or the second metrology measurement comprises a process parameter of a lithography tool in manufacturing one or more layers of the sample.

10. 10. The metrology target of claim 9, wherein the one or more process parameters include at least one of a focus position of the sample or an illumination dosage on the sample when exposing any of the one or more layers of the sample in the lithography tool.

11. 2. The metrology target of claim 1, wherein at least one of the first metrology measurement or the second metrology measurement comprises an overlay metrology measurement, a critical dimension metrology measurement, or a sidewall angle measurement.

12. 2. The metrology target of claim 1, wherein at least one of the first metrology measurement or the second metrology measurement comprises: At least one of the size, location, or orientation of one or more print elements on the sample.

13. A metrology target comprising:

Images