Metrologic systems 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] This disclosure generally relates to overlay metrology, and more particularly to targets suitable for a scanning overlay metrology system.

Background Art

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 867,142, entitled Scan Overlay (OVL) Target, filed on Jun. 26, 2019, under the names of inventors Andy Hill, Amnon Manassen, Gilad Laredo, Yoel Feler, Mark Ghinovker, and Vladimir Levinski, under 35 U.S.C. § 119(e), which is hereby incorporated by reference in its entirety.

[0003] Metrology systems typically provide in-product metrology by analyzing dedicated metrology targets, where the characteristics of the fabricated pattern elements indicate one or more metrology metrics of interest. Due to, but not limited to, the shrinking of design rules for in-product metrology, such as in-product overlay (OPO) metrology, and increasing specification requirements, the sampling requirements at multiple levels of the semiconductor manufacturing process are increasing. This increase in sampling may further enable higher complexity in the overlay model and more accurate corrections for the lithography system according to the metrology data.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, increasing sampling requirements can negatively impact the throughput of metrology. Therefore, it is 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 illustrative embodiments of the present disclosure. In one illustrative embodiment, the system includes a controller coupled to a scanning metrology tool, which images a sample moving along a scanning direction. In another illustrative embodiment, the controller receives an image of a metrology target on the sample from the scanning metrology tool. In another illustrative embodiment, the metrology target includes a first group of measurements comprising one or more cells dispersed along a transverse direction on the sample, where this transverse direction on the sample is perpendicular to the scanning direction. In yet another illustrative embodiment, the metrology target further includes a second group of measurements comprising one or more cells dispersed along a transverse direction on the sample, where the second group of measurements is separated from the first group of measurements along the scanning direction. In yet another illustrative embodiment, the controller generates at least a first metrology measurement based on at least one of the cells in a first set in the first metrology group. In yet another illustrative embodiment, the controller generates at least a second metrology measurement based on at least one of the cells in a second set in a second metrology group.

[0007] A metrological system is disclosed according to one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the system includes a scanning metrological tool for imaging a sample moving along a scanning direction. In another illustrative embodiment, the system includes a controller coupled to the scanning metrological tool. In another illustrative embodiment, the controller receives an image of a metrological target on the sample from the scanning metrological tool. In another illustrative embodiment, the metrological target includes a first group of measurements comprising one or more cells dispersed along a transverse direction on the sample, where this transverse direction on the sample is perpendicular to the scanning direction. In another illustrative embodiment, the metrological target further includes a second group of measurements comprising one or more cells dispersed along a transverse direction on the sample, where the second group of measurements is separated from the first group of measurements along the scanning direction. In another illustrative embodiment, the controller generates at least a first metrological measurement based on at least one of the cells of a first set in the first group of measurements. In another illustrative embodiment, the controller generates at least a second metrological measure based on at least one of the cells in a second set in a second metrological group.

[0008] A metrological target is disclosed according to one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the target includes a first measurement group comprising one or more cells dispersed along a transverse direction on a sample, where this transverse direction on the sample is perpendicular to the scanning direction. In another illustrative embodiment, one or more cells in the first measurement group can be measured simultaneously by a scanning metrological tool, and when measured using the scanning metrological tool, can further provide at least a first metrological measurement. In another illustrative embodiment, the target includes a second measurement group comprising one or more cells dispersed along a transverse direction on a sample, where the second measurement group is separated from the first measurement group along the scanning direction. In yet another illustrative embodiment, one or more cells in the second measurement group can be measured simultaneously by a scanning metrological tool, and when measured using the scanning metrological tool, can further provide at least a second metrological measurement.

[0009] It should be understood that the above general description and the following detailed description are merely illustrative and descriptive, and do not necessarily limit the claimed invention. The accompanying drawings incorporated herein and constituting part thereof illustrate embodiments of the invention and, together with the general description, serve to illustrate the principles of the invention.

[0010] Many of the advantages of this disclosure can be better understood by those skilled in the art by referring to the accompanying figures. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing a scanning metrology system according to one or more embodiments of the present disclosure. [Figure 2] This is a top view of a static metrologist suitable for static modal metrologistic measurements in which the sample is stationary during measurement, according to one or more embodiments of the present disclosure. [Figure 3] This is a conceptual diagram of a scanning metrology target according to one or more embodiments of the present disclosure. [Figure 4A] This is a top view of a scanning metrology target having two sets of measurements for overlay metrology aligned orthogonally, according to one or more embodiments of the present disclosure, wherein the cells within each of these two sets of measurements exhibit rotational symmetry. [Figure 4B] This is a top view of a scanning metrology target having two sets of measurements for overlay metrology aligned orthogonally, according to one or more embodiments of the present disclosure, wherein the cells within each of these two sets of measurements exhibit rotational symmetry. [Figure 4C] This is a top view of a scanning metrology target having multiple identical cells according to one or more embodiments of the present disclosure. [Figure 4D] This is a top view of a scanning metrology target having two measurement groups according to one or more embodiments of the present disclosure, wherein the cells within each of these two measurement groups exhibit reflection symmetry. [Figure 5]This is a top view of a scanning metrology target having two cell groups, each having three cells, which are for overlay metrology aligned orthogonally, according to one or more embodiments of the present disclosure. [Modes for carrying out the invention]

[0012] The subject matter disclosed herein is shown in detail below in relation to the attached drawings. This disclosure is shown and described in particular in relation to specific embodiments and their particular features. The embodiments shown herein should be construed as illustrative examples and not as limiting. It will be readily apparent to those skilled in the art that various modifications and variations in form and detail can be made without departing from the spirit and scope of this disclosure.

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

[0014] A metrological target typically includes clearly defined printed elements designed to provide an accurate representation of one or more printing properties. In this regard, the measured properties (e.g., by metrological tools) of the printed elements of a metrological target can represent the printed device elements associated with the device being manufactured. Furthermore, a metrological target is typically characterized as having one or more measurement cells, each cell containing printed elements in one or more layers on the sample. In this case, metrological measurements can be based on measurements of any combination of size, orientation, or location (e.g., pattern arrangement) of the printed elements within a single cell or between multiple cells.

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

[0016] A metrological system can inspect metrological targets using various techniques. For example, a metrological system can inspect a metrological target using a move-and-measure (MAM) operating mode, where the sample is translated to place the metrological target of interest within the measurement field, the measurement is performed while the sample is stationary, and the sample is then translated to place an additional metrological target of interest within the measurement field. As another example, a metrological system can inspect metrological targets while the sample is in motion (e.g., in scanning operating mode). For example, a scanning metrological tool can continuously analyze a sample while it is being scanned along the scanning direction through the measurement field. Furthermore, a scanning metrological tool can effectively inspect multiple adjacent targets dispersed along the scanning direction in a single scan, eliminating the time-consuming settling time requirement associated with MAM tools. Scanning metrology tools are generally described in U.S. Patent Application No. 15 / 761,830, filed on 21 March 2018, which is incorporated herein by reference.

[0017] Embodiments of the present disclosure are directed to metrology targets suitable for inspections using a scanning operation mode. It is recognized herein that due to different operation modes, scanning metrology tools have different error sources than MAM metrology tools. Specifically, MAM metrology tools can capture images of one or more cells in a single frame, while scanning metrology tools typically generate images line by line while the sample is being scanned. Thus, scanning metrology tools can be sensitive to errors that vary over time, such as vibration errors or jitter errors, that affect various parts of the image to various degrees, among others.

[0018] Thus, a scanning metrology target (and similarly a system for measuring such a target) designed in accordance with the present disclosure includes one or more measurement groups, where the measurement groups include one or more cells designed for a common metrology measurement dispersed along a direction perpendicular to the scanning direction of the sample. In this regard, the cells within each measurement group are inspected simultaneously to mitigate the effects of errors that vary over time during measurement. For example, measurement errors such as scanning speed error or scanning position error are common to all cells within each measurement group, which can facilitate a consistent and accurate measurement of the cells within the measurement group.

[0019] Furthermore, a scanning metrology target designed in accordance with the present disclosure can include any number of measurement groups dispersed along the scanning direction. Errors that vary over time can affect the cells within one measurement group differently than the cells within different measurement groups, but since metrology measurements typically (but not exclusively) encompass the cells within a single measurement group, these errors can have a minimal impact on the metrology measurements.

[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 measurements in a first direction (e.g., the X - direction), and a second measurement group having cells suitable for overlay measurements in an orthogonal second direction (e.g., the Y - direction). As another example, a scanning metrology target can include cells suitable for overlay measurements in both a first direction and a second direction within a common measurement group.

[0021] Additional embodiments of the present disclosure are directed to scanning metrology tools suitable for analyzing the scanning metrology targets described herein. For example, a scanning metrology tool can continuously analyze a scanning metrology target while the scanning metrology target is moving relative to a measurement field, receive metrology signals associated with each cell group, and generate metrology data from the metrology signals. Further, the scanning metrology tool can also apply a common measurement algorithm to cells within 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, a pattern mask can include pattern elements suitable for being imaged in a lithography system on a sample for manufacturing a scanning metrology target. Specifically, a pattern mask can include pattern elements within one or more cells of one or more cell groups associated with a particular layer to be manufactured on a sample. Further, a plurality of pattern masks can include pattern elements for manufacturing on a plurality of sample layers for manufacturing a multi - layer scanning metrology target (e.g., a scanning overlay target, etc.).

[0023] Hereinafter, referring to FIGS. 1 to 4, a system and method for metrology using a scanning metrology target will be described in more detail.

[0024] Figure 1 is a block diagram showing a scanning metrology system 100 according to one or more embodiments of the present disclosure. The scanning metrology system 100 may include various components for analyzing the sample 102 or a portion thereof while the sample 102 is being scanned against 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 being scanned, the sample 102 will be 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, which includes one or more components for guiding the illumination beam 106 over the sample 102. In yet another embodiment, the scanning metrology system 100 includes a focusing path 110, which includes one or more components for focusing the sample radiation 112. In yet 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 focusing path 110. In yet another embodiment, the scanning metrology system 100 includes a scanning subsystem (e.g., one or more translational stages, beam scanners, etc.) configured to adjust the sample 102 and / or the illumination beam 106 prior to, during, and / or after the 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, one or more processors 118 are configured to execute a set of program instructions held in a memory medium 120, i.e., memory. Furthermore, the controller 116 may include one or more modules containing one or more program instructions stored in the memory medium 120 that can be executed by the processors 118. The processors 118 of the controller 116 may include any processing elements known in the art. In this sense, the processors 118 may include any microprocessor-type devices configured to execute algorithms and / or instructions. In one embodiment, the processors 118 may consist of 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 a program configured to operate the scanning metrology system 100 as described throughout this disclosure. It is further recognized that the term “processor” may be broadly defined to include any device having one or more processing elements that execute program instructions from a non-temporary memory medium 120.

[0027] The memory medium 120 may include any storage medium known in the art that is suitable for storing program instructions that can be executed by the associated processor 118. For example, the memory medium 120 may include a non-temporary memory medium. As an additional example, the memory medium 120 may include, but is not limited to, read-only memory, random-access memory, magnetic or optical memory devices (e.g., disks), magnetic tape, solid-state drives, etc. It should be further noted that the memory medium 120 may be housed in a common controller housing having the processor 118. In one embodiment, the memory medium 120 may be located remotely from the physical locations of the processor 118 and the controller 116. For example, the processor 118 of the controller 116 may have access to remote memory (e.g., a server) that can be accessed via a network (e.g., the internet, an intranet, etc.). The foregoing description should not be construed as a limitation on the invention, and the foregoing description is merely illustrative.

[0028] The controller 116 can communicate and couple with 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 from the detector 114 a metrological signal (e.g., one or more images, etc.) associated with the scanning metrology target. 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 position, velocity, or other relevant parameters. In another embodiment, the controller 116 analyzes or processes the metrological signal from the detector 114 in another way. For example, the controller 116 may generate metrological data based on metrological signals from the scanning metrology target, including but not limited to overlay data, the focal position of the sample 102 during one or more lithography steps, or the amount of illumination applied during one or more lithography steps. In another embodiment, the controller 116 can generate one or more control signals to instruct or otherwise control components of the scanning metrology system 100. The controller 116 can generate control signals for any component of the scanning metrology system 100, including but not limited to the detector 114, the sample stage 134, and the illumination source 104, or for any component of the illumination path 108 or the focusing path 110.

[0029] Furthermore, the scanning metrology system 100 can also operate as any type of metrology system known in the art. In one embodiment, the scanning metrology system 100 is an imaging metrology system that can generate metrology data based on one or more images of a sample 102. In another embodiment, the scanning metrology system 100 is a scattering metrology system, where 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] Furthermore, with reference to Figure 1, the various components of the scanning metrology system 100 will be described in more detail.

[0031] The illumination source 104 may include any type of light source known in the art. Furthermore, 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 one or more laser sources, but is not limited thereto. In this regard, the illumination source 104 can produce an illumination beam 106 with high coherence (e.g., high spatial coherence and / or temporal coherence). For example, the illumination source 104 may include one or more broadband lasers, such as one or more supercontinuum lasers or white light lasers, but is not limited thereto. As another example, the illumination source 104 may include one or more narrowband lasers. As yet another example, the illumination source 104 may include one or more tunable lasers to provide an illumination beam 106 with tunable spectral intensity. Furthermore, the coherent illumination source 104 may be based on any type of technology or product design. For example, the illumination source 104 may include any combination of one or more fiber lasers, one or more diode lasers, or one or more gas lasers, but is not limited thereto.

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

[0034] Furthermore, the illumination source 104 may include any combination of light sources. In one embodiment, the illumination source 104 includes one or more supercontinuum laser sources for providing broadband illumination, and one or more partially coherent high-brightness LEDs for filling 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 sustained wave sources for providing a sustained 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 may include one or more mode-locked lasers, one or more Q-switched lasers, and so on.

[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 adjusting 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 an illumination beam 106 onto a sample 102.

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

[0039] In one embodiment, the focusing path 110 includes one or more lenses 128. In another embodiment, the focusing path 110 includes one or more optical components 130 suitable for modifying and / or adjusting 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 Figure 1, the beam splitter 132 may be common to both the illumination path 108 and the focusing path 110 so that the objective lens 126 can perform both guiding the illumination beam 106 to the sample 102 and focusing the sample radiation 112. In another embodiment, not shown, the illumination path 108 and the focusing path 110 may each include separate lenses for guiding the illumination beam 106 to the sample 102 and for focusing the sample radiation 112, respectively.

[0041] The detector 114 may include any photodetector known in the art that is suitable for capturing sample radiation 112 received from 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) or a complementary metal-oxide semiconductor (CMOS) device. The detector 114 can be positioned in any imaging plane of the scanning metrology system 100. For example, the detector 114 can be positioned in a plane conjugate to sample 102 to generate an image of sample 102. In another example, the detector 114 can be positioned in the pupil plane (or its conjugate) to generate an pupil image.

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

[0043] In another embodiment, the scanning metrology system 100 includes a scanning subsystem for scanning a sample 102 relative to the measurement field during metrological measurement. In one embodiment, as shown in Figure 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, but is not limited to them, such as a linear translation stage, a rotation stage, or a tip / tilt stage. In another embodiment, not shown, the scanning subsystem includes one or more beam scanning optics (e.g., a rotatable mirror, a galvanometer, etc.) for scanning an illumination beam 106 relative to the sample 102.

[0044] The detector 114 can be configured to generate a metrological signal (e.g., a sample plane image and / or pupil plane image) while scanning using any technique known in the art. In one embodiment, the detector 114 includes a 2D pixel array having 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 scanning detector for continuously generating images of one line of pixels at a time. In yet another embodiment, the detector 114 includes a time-delay integration (TDI) detector. The TDI detector can generate a continuous image of sample 102 if the movement of sample 102 is synchronized with a charge transfer clock signal in the TDI detector. In detail, the TDI detector includes a clock pulse for acquiring charge from exposure to a row of pixels and for transferring charge between adjacent rows of pixels along the scanning direction. If the movement of sample 102 along the scanning direction is synchronized with charge transfer in the TDI detector, charge accumulates continuously during scanning. This process continues until the charge reaches the last row of pixels, which are then read out from the detector. This method allows for the accumulation of images of the target over longer time frames than would be possible with a single-line scanning camera. This relatively longer acquisition time results in lower levels of photon noise in the image. Furthermore, the synchronized movement of the image and charge prevents blurring in the recorded image.

[0045] Next, we will refer to Figures 2 through 4 to explain various metrological target designs in more detail.

[0046] Figure 2 is a top view of a static metrology target 202 suitable for static mode (e.g., frame mode) metrology measurements in which the sample 102 is stationary during measurement, according to one or more embodiments of the present disclosure.

[0047] For example, the static metrology target 202 in Figure 2 may, in some cases, be suitable for overlay metrology to determine the positioning error between two layers of sample 102. In detail, the static metrology target 202 can include four cells 204a-d, which are represented here as quadrants of the static metrology target 202. Each cell 204a-d can include a first layer printing element 206 positioned on the first layer of sample 102, and a second layer printing element 208 positioned on the second layer of sample 102.

[0048] Furthermore, cells 204a and 204d can be configured to provide overlay measurements along the X direction as shown in Figure 2. For example, overlay measurements along the X direction can be performed by directly comparing the relative positions of the first layer printing elements 206 and the second layer printing elements 208 within each cell or between cells 204a and 204d. In another example, overlay measurements along the X direction can be performed by comparing points of rotational symmetry (e.g., rotational symmetry, reflection symmetry, specular symmetry, etc.) between the first layer printing elements 206 distributed across cells 204a and 204d with points of symmetry between the second layer printing elements 208 distributed across cells 204a and 204d. Similarly, cells 204b and 204c can be configured to provide overlay measurements along the Y direction as shown in Figure 2.

[0049] In this specification, it is recognized that a metrological tool configured for static measurement (e.g., MAM operating mode) can capture an image of the static metrological target 202 in a single measurement field of view 210 (e.g., a single frame). Therefore, the effect of time-varying errors of the metrological tool on the metrological measurement can generally be limited to the effect of time-varying errors occurring in a time frame of approximately the exposure time required to generate all images of the static metrological target 202. Furthermore, since all cells 204a to 204d are imaged simultaneously in a single image, all time-varying errors will have a common effect on various parts of the image. In this regard, time-varying errors usually cannot introduce a difference between the part of the image associated with cell 204a (or cell 204b) and the part 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 measurement can generate line-by-line images of a static metrology target 202 while the sample 102 is being 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), which can directly affect the overlay metrology measurement.

[0051] Next, with reference to Figures 3 to 5, metrologists suitable for scanning mode measurements will be described according to one or more embodiments of this disclosure.

[0052] Figure 3 is a conceptual diagram of a scanning metrology target 302 according to one or more embodiments of the present disclosure.

[0053] In one embodiment, the scanning metrology target 302 includes a plurality of measurement cells 304 dispersed on a sample 102, each cell 304 containing printed elements designed to provide selected metrological measurements on one or more layers of the sample 102. For example, overlay metrology can determine the positioning error of a given layer by utilizing the relative positions between pattern elements on two or more layers of the sample 102 during lithography, with the pattern elements positioned within one or more cells 304 of the scanning metrology target 302. In another example, the cells 304 may, but are not limited to, contain printed elements on one or more sample layers, whose characteristics, such as size, limiting dimension (CD), or position, indicate one or more process parameters during exposure (e.g., focal position of the sample 102, illumination application amount, etc.).

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

[0055] In this specification, it is recognized that the scanning metrology system 100 may have multiple related error sources that may negatively affect its metrological performance. In particular, because the scanning metrology system 100 generates a continuous image along the scan, the effects of time-varying errors, such as vibration or jitter, may manifest as changes in a particular part of the continuous image relative to other parts (e.g., spatial changes in the continuous image), although these are not limited to the above. For example, an error associated with the scanning direction 308 may induce a lateral shift in a particular part of the continuous image along the lateral direction. As another example, an error associated with the translational velocity (e.g., scanning speed) along the scanning direction 308 may manifest as stretching or shrinking of a part of the continuous image.

[0056] In the context of metrology, spatial variations in sequential images due to system-induced errors can negatively impact the performance of metrological algorithms designed to extract information about a sample from 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 sample 102. However, spatial variations in the image can, in some cases, directly affect the location of features in the image and thus directly contribute to measurement errors. As another example, limiting dimensional metrology can measure the size of features on a sample based on the size of features in the image. However, spatial variations in the image can, in some cases, directly affect the imaged size of features at different locations along the scanning direction 308 and thus directly contribute to inconsistent measurement results along the scanning direction 308.

[0057] Accordingly, in embodiments of this disclosure, cells 304 associated with a common metrological measurement can be arranged to be located within a common measurement group 306. In this regard, cells 304 within each measurement group 306 can be measured simultaneously to mitigate the effects of time-varying errors. It is recognized herein that time-varying errors may still affect cells 304 within each measurement group 306. However, only time-varying errors occur on a timescale of the measurement time of the measurement group 306 (e.g., approximately the size of the largest cell 304 measured along the scanning direction 308). Furthermore, even these errors occurring on this timescale will similarly affect all cells 304 within the measurement group 306.

[0058] However, it should be understood that the metrological algorithm does not preemptively exclude the use of cell 304 in different measurement groups 306. In this specification, it is merely intended that increasing the size of a portion of the analyzed image along the scanning direction 308 may increase the influence of time-varying errors.

[0059] The scanning metrology target 302 may include any selected number of measurement groups 306, each measurement group 306 containing any number of cells 304 suitable for any selected metrological measurement. In one embodiment, the scanning metrology target 302 may include a first measurement group 306 having one or more cells 304 designed to provide overlay measurements along a first direction (e.g., the X direction), and a second measurement group 306 having one or more cells 304 designed to provide overlay measurements along a second direction (e.g., the 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 metrological 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 may include one or more cells 304 in a common measurement group 306 designed to provide overlay measurements along multiple directions (e.g., the X and Y directions). In this regard, cells 304 in a common set of measurements 306 associated with overlay metrology along multiple directions can be measured simultaneously. In another embodiment, a scanning metrology target 302 includes one or more cells 304 in a common set of measurements 306 designed to provide CD metrology, thereby minimizing or otherwise mitigating the effect of time-varying errors on CD measurements for features at different locations within the scanning metrology target 302. In another embodiment, a scanning metrology target 302 includes one or more cells 304 in a common set of measurements 306 designed to provide process metrology data (e.g., illumination application amount, focal position, etc., in a lithography tool), thereby minimizing or otherwise mitigating the effect of time-varying errors on process metrology measurements. Therefore, it should be understood that examples of providing a particular number or particular layout of measurements 306 within a scanning metrology target 302 are provided merely as illustrations and should not be interpreted as limiting.

[0060] In one embodiment, the scanning metrology target 302 includes one or more measurement groups 306, where various measurement groups 306 within each measurement group 306 provide metrological 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 a cell 304 that provides metrological measurements along a first direction, and a second measurement group 306 that may include a cell 304 that provides metrological measurements along a second direction different from the first direction. The first and second directions may be orthogonal, but are not necessarily so. Furthermore, the first and second directions may correspond to the scanning direction 308 and the transverse direction 310, but are not necessarily so.

[0061] Therefore, the measurement group 306 may include cells 304 having printed elements having any selected pattern suitable for providing a metrological measurement of selected interest. In one embodiment, the measurement group 306 includes 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. Furthermore, the multiple elements may, though not necessarily, have a common size.

[0062] Next, with reference to Figures 4A to 5, various configurations of the scanning metrology target 302 will be described according to one or more embodiments of this disclosure. For example, in this specification, the overlay can be designed to provide overlay measurements based on any measurement algorithm known in the art. For example, overlay measurements along the measurement direction can be generated by directly comparing points of relative position or symmetry (e.g., rotational symmetry, reflection symmetry, etc.) of printed elements generated using different exposure steps. Furthermore, while the configurations of the scanning metrology target 302 shown in Figures 4A to 5 are designed for overlay metrology, it should be understood that the scanning metrology target 302 configured according to this disclosure is not limited to overlay metrology. Thus, in this specification, it is intended that those skilled in the art can extend the features and operating principles described in the embodiments illustrated herein to additional metrology target designs.

[0063] Figure 4A is a top view of a scanning metrology target 302 having two sets of measurements 306a, b for orthogonal overlay metrology according to one or more embodiments of the present disclosure, wherein the cells 304 within each of these two sets of measurements 306a, b exhibit rotational symmetry.

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

[0065] Furthermore, any cell among cells 304a to 304d may include a cell 304 having printed elements having any selected pattern suitable for providing a metrological measurement of selected interest. For example, measurement group 306a and / or measurement group 306b may include at least one cell 304 having periodic printed elements. For example, a periodic printed element may include multiple (e.g., three or more) elements having a common spacing along a selected direction. Furthermore, the multiple elements may, though not necessarily, have a common size.

[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., the 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., the 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 effect of time-varying errors on the relevant metrological 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 effect of time-varying errors on the relevant metrological measurements along the second direction.

[0067] Furthermore, the scanning metrology target 302 in Figure 4A may be well suited for overlay metrology based on the rotational symmetry of cell 304, though not limited to it. For example, cell 304b can be designed to accommodate a 180-degree rotation of cell 304a in the absence of overlay error, so that an overlay measurement along the X direction can be generated by comparing the rotationally symmetric point 406 of the first set of printed elements 402 in measurement group 306a with the rotationally symmetric point 408 of the second set of printed elements 404 in measurement group 306a. Similarly, in Figure 4A, cell 304d can be designed to accommodate a 180-degree rotation of cell 304c in the absence of overlay error, so that an overlay measurement along the Y direction can be generated by comparing the rotationally symmetric point 410 of the first set of printed elements 402 in measurement group 306b with the rotationally symmetric point 412 of the second set of printed elements 404 in measurement group 306b. In this regard, the measurement of the rotationally symmetric cell 304 can reduce or otherwise minimize the rotational error of the scanning metrology system 100.

[0068] In this specification, it is intended that various arrangements of elements within the cells 304 of the measurement group 306 can provide desired symmetry. Figure 4B is a top view of a scanning metrology target 302 having two measurement groups 306a, b for orthogonal overlay metrology according to one or more embodiments of the present disclosure, where the cells 304 within each of these two measurement groups 306a, b exhibit rotational symmetry. In detail, the cells 304c, d in measurement group 306b in Figure 4B are dispersed along the Y direction (e.g., the measurement direction), and the length of measurement group 306b along the Y direction is longer compared to the scanning metrology target 302 in Figure 4A.

[0069] In this specification, the scanning metrology target 302 is suitable for scanning in multiple directions, and it is further intended that a common target can be used to facilitate the comparison of measurements obtained along different directions. For example, the scanning metrology target 302 in Figure 4B can be scanned along the X direction (for example, the scanning directions 308 and lateral direction 310 shown in Figure 4B can be interchanged).

[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 interpreted as restrictive. Rather, the scanning metrology target 302 (or any group of cells 304 in the measurement group 306) could correspond to versions rotated by any amount (e.g., 45 degrees, 90 degrees, etc.) relative to each other.

[0071] Furthermore, as already described herein, the cell 304 in the measurement group 306 does not need to 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 according to one or more embodiments of the present disclosure. Thus, overlay measurements along the Y direction can be generated by performing overlay measurements individually on cells 304c and 304d (for example, based on the relative positions and / or symmetric points 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 the rotational error 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., specular symmetry, 1-D symmetry, etc.) along a desired measurement direction (e.g., X direction, Y direction, etc.). Figure 4D is a top view of a scanning metrology target 302 having two measurement groups 306a, b according to one or more embodiments of the present disclosure, where the cells 304 in each of these two measurement groups 306a, b exhibit reflection symmetry. For example, the first set of printed elements 402 and the second set of printed elements 404 in measurement group 306a can be designed to be symmetric about an axis 414 so that overlay measurements along the X direction can be associated with a comparison of the axis of symmetry of the first set of printed elements 402 in measurement group 306a and the axis of symmetry of the second set of printed elements 404 in measurement group 306a. Similarly, the first set of printed elements 402 and the second set of printed elements 404 in the measurement group 306b can be designed to be symmetrical around axis 416 so that overlay measurements along the Y direction can be associated with a comparison between the axis of symmetry of the first set of printed elements 402 in the measurement group 306b and the axis of symmetry of the second set of printed elements 404 in the measurement group 306b.

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

[0075] In another embodiment, a particular cell 304 may include pattern elements (e.g., grids, etc.) with deliberately inserted skew (e.g., offset). In this regard, the metrological measurement of cell 304 can be used to provide residual minimization by algorithm and / or flag.

[0076] However, it should be understood that the examples of measurement groups 306 having two cells 304, as shown in Figures 4A to 4D, are provided for illustrative purposes only and should not be interpreted as limiting. The measurement groups 306 of the scanning metrology target 302 can contain any number of cells 304.

[0077] Figure 5 is a top view of a scanning metrology target 302 having two measurement groups 306, each having three cells 304, which are for overlay metrology aligned orthogonally, according to one or more embodiments of the present disclosure. For example, the scanning metrology target 302 may include a first measurement group 306a having cells 304a-c, and a second measurement group 306b having cells 304d-f. Furthermore, as shown in Figure 5, the symmetry between the cells 304 may differ between the different measurement groups 306. For example, the first measurement group 306a may include cells 304 having two rotational deformation forms, while the second measurement group 306b may include the exact same cells 304.

[0078] The subjects described herein illustrate different components that are sometimes contained within or connected to other components. It should be understood that such described architectures are merely illustrative, and that in fact, many other architectures that achieve the same functionality are possible. Conceptually, components of any structure for achieving the same functionality are effectively "related" in such a way that the desired functionality is achieved. Therefore, in this specification, any two components combined to achieve a particular functionality can be considered "related" to each other in such a way that the desired functionality is achieved independently of the architecture or intermediate components. Similarly, any two components that are related in this way can likewise be considered "connected" or "combined" to each other in order to achieve the desired functionality, and any two components that can be related in this way can likewise be considered "combinable" to each other in order to achieve the desired functionality. Specific examples of connectable components include, but are not limited to, physically interactable components and / or components that interact physically, and / or wirelessly interactable components and / or components that interact wirelessly, and / or logically interactable components and / or components that interact logically.

[0079] The present disclosure and its many associated advantages should be understood from the above description, and it will be clear that various modifications can be made to the form, structure, and arrangement of components without departing from the disclosed subject matter or sacrificing all of its essential advantages. The described form is merely illustrative, and the following claims encompass and are intended to encompass such modifications. Furthermore, it should be understood that the present invention is defined by the appended claims.

Claims

1. A metrological system, Metrics targets and A scanning metrology tool that measures the aforementioned metrology target in a scanning operation mode, A controller coupled to the aforementioned scanning metrology tool, Equipped with, The aforementioned metrological target is, A first measurement group comprising one or more cells dispersed along the transverse direction on a sample, wherein the transverse direction on the sample is perpendicular to the scanning direction, and the one or more cells in the first measurement group are configured to be measured simultaneously by the scanning metrology tool, and are further configured to provide at least a first metrology measurement to the controller when measured using the scanning metrology tool, A second measurement group comprising one or more cells dispersed along the lateral direction on the sample, wherein the second measurement group is separated from the first measurement group along the scanning direction, and the one or more cells in the second measurement group are configured to be measured simultaneously by the scanning metrology tool, and are further configured to provide at least a second metrology measurement to the controller when measured using the scanning metrology tool. A metrological system characterized by comprising the following features.

2. A metrological system according to claim 1, wherein the metrological target comprises one or more additional measurement groups, each including one or more cells dispersed along the lateral direction on the sample, the one or more additional measurement groups being separated from the first measurement group and the second measurement group along the scanning direction, the one or more cells in each of the one or more additional measurement groups being configured to be measured simultaneously by the scanning metrological tool, and further configured to provide at least additional metrological measurements to the controller when measured using the scanning metrological tool.

3. A metrological system according to claim 1, The first metrological measurement includes an overlay metrological measurement along the first direction on the sample, The second metrological measurement includes an overlay metrological measurement along a second direction different from the first direction on the sample. A metrological system characterized by the following:

4. A metrological system according to claim 3, characterized in that the overlay metrological measurement along the first direction on the sample is based on the relative positions of two or more sets of printed elements in one or more cells of the first measurement group, and the overlay metrological measurement along the second direction on the sample is based on the relative positions of two or more sets of printed elements in one or more cells of the second measurement group.

5. A metrological system according to claim 3, wherein the first measurement group comprises two or more cells, and the overlay metrological measurement along the first direction on the sample is based on the relative positions of the rotationally symmetric centers of two or more sets of printed elements dispersed across the two or more cells in the first measurement group, and the second measurement group comprises two or more cells, and the overlay metrological measurement along the second direction on the sample is based on the relative positions of the rotationally symmetric centers of two or more sets of printed elements dispersed across the two or more cells in the second measurement group.

6. A metrological system according to claim 3, wherein the first measurement group comprises two or more cells, and the overlay metrological measurement along the first direction on the sample is based on the relative positions of the reflection symmetry axes of two or more sets of printed elements dispersed across the two or more cells in the first measurement group, and the second measurement group comprises two or more cells, and the overlay metrological measurement along the second direction on the sample is based on the relative positions of the reflection symmetry axes of two or more sets of printed elements dispersed across the two or more cells in the second measurement group.

7. A metrological system according to claim 1, characterized in that at least one of the first set of cells or the second set of cells includes two or more identical cells.

8. A metrological system according to claim 1, characterized in that at least one of the first measurement group or the second measurement group includes a cell having one set of periodic printing elements.

9. A metrological system according to claim 1, characterized in that at least one of the first metrological measurement or the second metrological measurement includes process parameters of a lithography tool used to produce one or more layers of the sample.

10. A metrological system according to claim 9, characterized in that one or more process parameters include at least one of the focal position of the sample or the amount of illumination applied to the sample when any of the one or more layers of the sample is exposed in the lithography tool.

11. A metrological system according to claim 1, characterized in that at least one of the first metrological measurement or the second metrological measurement includes an overlay metrological measurement, a limit dimension metrological measurement, or a side wall angle measurement.

12. The metrological system according to claim 1, wherein at least one of the first metrological measurement or the second metrological measurement is The size, location, or orientation of one or more printed elements on the aforementioned sample A metrological system characterized by including [this].

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