Measurement targets used for scanning measurement

Abstract

This application relates to metrological targets for scanning metrology. A metrology system may include a controller coupled to a scanning metrology tool that images a sample moving along a scanning direction. The controller may receive images of metrological targets on the sample from the scanning metrology tool, wherein the metrological targets include: a first measurement group comprising units distributed along a lateral direction orthogonal to the scanning direction; and a second measurement group separated from the first measurement group along the scanning direction, the second measurement group comprising units distributed along the lateral direction. The controller may further generate at least a first metrological measurement based on at least one of the first group of units in the first metrological group, and generate at least a second metrological measurement based on at least one of the second group of units in the second metrological group.

Description

[0001] Information related to divisional application

[0002] This application is a divisional application of the invention patent application filed on June 24, 2020, with application number 202080040950.0 and invention title "Metrological Target for Scanning Measurement".

[0003] Cross-citation of related applications

[0004] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 867,142, entitled “Scan Overlay (OVL) Target,” filed June 26, 2019, entitled “Scan Overlay (OVL) Target,” which designates Andy Hill, Amnon Manassen, Gilad Laredo, Yoel Feler, Mark Ghinovker, and Vladimir Levinski as inventors, pursuant to 35 U.S. SC §119(e), the entire contents of which are incorporated herein by reference. Technical Field

[0005] This disclosure generally relates to overlap metrology, and more specifically, to targets applicable to scanning overlap metrology systems. Background Technology

[0006] Metrology systems typically provide on-product metrology by analyzing specific metrological targets, where the characteristics of manufactured patterned elements indicate one or more metrological parameters of interest. Tightening design rules and increasingly stringent specifications for on-product metrology (e.g., but not limited to, on-product overlap (OPO) metrology) are driving increased sampling requirements at multiple levels of the semiconductor manufacturing process. This increased sampling can further enable greater complexity in overlap models and more accurate, calibrable values ​​for lithography systems in response to metrological data. However, increased sampling requirements can negatively impact metrological throughput. Therefore, systems and methods for high-throughput metrology are desired. Summary of the Invention

[0007] A metrology system according to one or more illustrative embodiments of the present disclosure is disclosed. In one illustrative embodiment, the system includes a controller coupled to a scanning metrology tool, wherein the scanning metrology tool images a sample moving along a scanning direction. In another illustrative embodiment, the controller receives an image of a metrological target on the sample from the scanning metrology tool. In another illustrative embodiment, the metrological target includes a first measurement group comprising one or more units distributed along a lateral direction on the sample, wherein the lateral direction on the sample is orthogonal to the scanning direction. In another illustrative embodiment, the metrological target further includes a second measurement group comprising one or more units distributed along the lateral direction on the sample, wherein the second measurement group is separated from the first measurement group along the scanning direction. In another illustrative embodiment, the controller generates at least a first metrological measurement based on at least one of the first group of units in the first metrological group. In another illustrative embodiment, the controller generates at least a second metrological measurement based on at least one of the second group of units in the second metrological group.

[0008] A metrology system according to one or more illustrative embodiments of the present disclosure is disclosed. In one illustrative embodiment, the system includes a scanning metrology tool for imaging a sample moving along a scanning direction. In another illustrative embodiment, the system includes a controller coupled to the scanning metrology tool. In another illustrative embodiment, the controller receives an image of a metrological target on the sample from the scanning metrology tool. In another illustrative embodiment, the metrological target includes a first measurement group comprising one or more units distributed along a lateral direction on the sample, wherein the lateral direction on the sample is orthogonal to the scanning direction. In another illustrative embodiment, the metrological target further includes a second measurement group comprising one or more units distributed along the lateral direction on the sample, wherein the second measurement group is separated from the first measurement group along the scanning direction. In another illustrative embodiment, the controller generates at least a first metrological measurement based on at least one of the first group of units in the first metrological group. In another illustrative embodiment, the controller generates at least a second metrological measurement based on at least one of the second group of units in the second metrological group.

[0009] A metrological target according to one or more illustrative embodiments of the present disclosure is disclosed. In one illustrative embodiment, the target includes a first measurement group comprising one or more units distributed along a lateral direction on a sample, wherein the lateral direction on the sample is orthogonal to the scanning direction. In another illustrative embodiment, the one or more units in the first measurement group can be simultaneously measured by a scanning metrology tool and can further provide at least a first metrological measurement when measured with the scanning metrology tool. In another illustrative embodiment, the target includes a second measurement group comprising one or more units distributed along the lateral direction on the sample, wherein the second measurement group is separated from the first measurement group along the scanning direction. In another illustrative embodiment, the one or more units in the second measurement group can be simultaneously measured by the scanning metrology tool and can further provide at least a second metrological measurement when measured with the scanning metrology tool.

[0010] It should be understood that both the foregoing overview and the following detailed description are exemplary and illustrative only and do not necessarily limit the invention as claimed. The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with the overview, serve to explain the principles of the invention. Attached Figure Description

[0011] Many advantages of this disclosure can be better understood by those skilled in the art with reference to the accompanying drawings, among which:

[0012] Figure 1 This is a block diagram illustrating a scanning measurement system according to one or more embodiments of the present disclosure.

[0013] Figure 2 This is a top view of a static metrological target suitable for static mode metrological measurements in which the sample is stationary during measurement, according to one or more embodiments of this disclosure.

[0014] Figure 3 This is a conceptual diagram of a scanning measurement target according to one or more embodiments of the present disclosure.

[0015] Figure 4A It is a top view of a scanned measurement target having two measurement groups for overlapping measurements along orthogonal directions, according to one or more embodiments of the present disclosure, wherein the cells within each of the two measurement groups exhibit rotational symmetry.

[0016] Figure 4B It is a top view of a scanned measurement target having two measurement groups for overlapping measurements along orthogonal directions, according to one or more embodiments of the present disclosure, wherein the cells within each of the two measurement groups exhibit rotational symmetry.

[0017] Figure 4CThis is a top view of a scanning measurement target having multiple identical units according to one or more embodiments of the present disclosure.

[0018] 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 the two measurement groups exhibit reflective symmetry.

[0019] Figure 5 This is a top view of a scan measurement target having two groups of three cells each for overlapping measurement along orthogonal directions, according to one or more embodiments of the present disclosure. Detailed Implementation

[0020] The disclosed subject matter will now be described in detail with reference to the accompanying drawings. This disclosure has been shown and described, in particular, with reference to certain embodiments and their specific features. The embodiments set forth herein should be considered illustrative rather than restrictive. It will 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 this disclosure.

[0021] Embodiments of this disclosure relate to systems and methods for scan-based metrology, wherein the metrological target is characterized by the metrological tool as it is translated through the focusing volume of the metrological tool.

[0022] A metrological target may typically comprise a well-defined printed element designed to provide an accurate representation of one or more printing characteristics. In this respect, the measurable characteristics of the printed element of the metrological target (e.g., by a metrological tool) may represent a printing apparatus element associated with a manufactured apparatus. Furthermore, a metrological target is typically characterized to have one or more measurement units, each containing a printed element in one or more layers on a sample. Metrological measurements may then be based on any combination of measurements of the size, orientation, or position (e.g., pattern placement) of the printed element within a single unit or between multiple units.

[0023] For example, one or more units of an overlapping metrology target may comprise printed elements on two or more sample layers arranged such that the relative positions of elements in each layer can indicate offset errors (e.g., pattern placement errors (PPE)) in a particular layer or overlap errors associated with registration errors between sample layers. As another example, a process-sensitive metrology target may comprise printed elements on a single sample layer, wherein one or more characteristics of said printed elements (e.g., width or critical dimension (CD), sidewall angle, position, or the like) indicate one or more process parameters, such as (but not limited to) the dose of illumination during a photolithography step or the focal position of the sample in the photolithography tool during a photolithography step.

[0024] A metrology system can use various techniques to verify metrological targets. For example, a metrology system can use a moving and measuring (MAM) operating mode to verify metrological targets, in which the sample is translated to place the metrological target of interest within the measurement field of view, a measurement is performed while the sample is static, and then the sample is translated again to place additional metrological targets of interest within the measurement field of view. As another example, a metrology system can verify metrological targets while the sample is in motion (e.g., in a scanning operating mode). For example, a scanning metrology tool can continuously analyze the sample as it is scanned across the measurement field along the scanning direction. Furthermore, a scanning metrology tool can efficiently verify multiple adjacent targets distributed along the scanning direction in a single scan, eliminating the time-consuming settling time requirements associated with MAM tools. Scanning metrology tools are substantially described in U.S. Patent Application No. 15 / 761,830, filed March 21, 2018, the entire contents of which are incorporated herein by reference.

[0025] Embodiments of this disclosure relate to metrological objectives suitable for inspections using scanning operating modes. It should be understood herein that, due to the different operating modes, scanning metrology tools have different error sources than MAM metrology tools. Specifically, 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 as the sample is scanned. Therefore, scanning metrology tools may be sensitive to time-varying errors (e.g., but not limited to, vibration or jitter errors that affect different portions of the image to varying degrees).

[0026] Therefore, the scanning metrology target (and system for measuring such target) designed according to this disclosure comprises one or more measurement groups, wherein the measurement group includes one or more units designed for common metrological measurements distributed along a direction orthogonal to the scanning direction of the sample. In this regard, the units within each measurement group are examined simultaneously to mitigate the effects of time-varying errors during measurement. For example, measurement errors (e.g., scanning speed or scanning position errors) are common to all units in each measurement group, which can help to achieve consistent and accurate measurements of the units within the measurement group.

[0027] Furthermore, the scanning metrology target designed according to this disclosure can comprise any number of groups distributed along the scanning direction. Although the effect of time-varying errors on cells within a single measurement group may differ from its effect on cells in different measurement groups, these errors may have minimal impact on metrology measurements because metrology measurements typically (but not exclusively) involve cells within a single measurement group.

[0028] A measurement group can comprise any combination of one or more units designed to generate any number of metrological measurements. For example, in the context of overlapping metrology, a scanning metrology target may comprise a first measurement group having units suitable for overlapping measurements in a first direction (e.g., the X direction) and a second measurement group having units suitable for overlapping measurements in an orthogonal second direction (e.g., the Y direction). By another example, a scanning metrology target may comprise units in a common measurement group suitable for overlapping measurements in both the first and second directions.

[0029] Additional embodiments of this disclosure relate to scanning metrology tools suitable for analyzing scanning metrology targets described herein. For example, the scanning metrology tool can continuously analyze the scanning metrology target as it moves relative to a measurement field, receiving metrology signals associated with each in a group of cells and generating metrology data from said metrology signals. Furthermore, the scanning metrology tool can apply a common measurement algorithm to the cells within each group of cells to generate metrology data from the corresponding metrology signals.

[0030] Additional embodiments of this disclosure relate to one or more pattern masks suitable for generating scanning metrology targets. For example, the pattern mask may include pattern elements suitable for imaging onto a sample in a lithography system for fabricating scanning metrology targets. Specifically, the pattern mask may include pattern elements in one or more cells of one or more cell groups associated with a particular layer to be fabricated on the sample. Further, multiple pattern masks may include pattern elements for fabricating on multiple sample layers to create multilayer scanning metrology targets (e.g., scanning overlapping targets or the like).

[0031] For reference Figure 1 Section 4 provides a more detailed description of the systems and methods used for measurement of scanning measurement targets.

[0032] Figure 1 This is a block diagram illustrating 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 a sample 102 or a portion thereof when scanning the sample 102 relative to a measurement field. For example, the scanning metrology system 100 may be configured to analyze scanning metrological targets on the sample 102 (which will be described in more detail below) when scanning the sample 102.

[0033] 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 for directing the illumination beam 106 to one or more components of the sample 102. In another embodiment, the scanning metrology system 100 includes a collection path 110 for collecting 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, or the like) configured to adjust the sample 102 and / or the illumination beam 106 before, during, and / or after measurement.

[0034] 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 maintained in memory medium 120 or memory. Further, the controller 116 may include one or more modules containing one or more program instructions executable by the processor 118 and stored in memory medium 120. 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 type device configured to execute algorithms and / or instructions. In one embodiment, the processor 118 may comprise a desktop computer, mainframe computer system, workstation, imaging computer, 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 should be further understood that the term "processor" can be broadly defined to cover any device having one or more processing elements that execute program instructions from the non-transitory memory medium 120.

[0035] Memory media 120 may comprise any storage medium known in the art suitable for storing program instructions executable by the associated processor 118. For example, memory media 120 may comprise a non-transitory memory medium. As additional examples, memory media 120 may comprise (but is not limited to) read-only memory, random access memory, magnetic or optical storage devices (e.g., magnetic disks), magnetic tape, solid-state drives, and the like. It should be further noted that memory media 120 may be housed together with processor 118 within a common controller housing. In one embodiment, memory media 120 may be remotely located relative to the physical location of processor 118 and controller 116. For example, processor 118 of controller 116 may access remote memory (e.g., a server) accessible via a network (e.g., the Internet, an intranet, and the like). Therefore, the above description should not be construed as limiting the invention, but is merely illustrative.

[0036] 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 metrological signals (e.g., one or more images or the like) associated with a scanning metrology target from the detector 114. In another embodiment, the controller 116 performs one or more processing steps of this disclosure. By another example, the controller 116 may receive position feedback indicating position, velocity, or other relevant parameters from the sample stage 134. In another embodiment, the controller 116 analyzes or otherwise processes the metrological signals from the detector 114. For example, the controller 116 may generate metrological data (e.g., but not limited to, overlap data, the focal position of the sample 102 during one or more lithography steps, or the illumination dose during one or more lithography steps) based on the metrological signals from the scanning metrology target. In another embodiment, the controller 116 may generate one or more control signals to guide or otherwise control the 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, detector 114, sample stage 134, illumination source 104 or illumination path 108 or collection path 110).

[0037] Furthermore, the scanning metrology system 100 can operate as any type of metrology system known in the art. In one embodiment, the scanning metrology system 100 is an imaging metrology system in which metrological data can be generated based on one or more images of the sample 102. In another embodiment, the scanning metrology system 100 is a scattering measurement metrology system in which the metrological data is based on one or more pupil images associated with the diffracted and / or scattered illumination beam 106 through the sample 102.

[0038] Still referencing Figure 1 The various components of the scanning measurement system 100 will be described in more detail.

[0039] The lighting source 104 may include any type of light source known in this art. Furthermore, the lighting source 104 may have any selected spectral content.

[0040] In one embodiment, illumination source 104 includes one or more coherent sources, such as (but not limited to) one or more laser sources. In this respect, illumination source 104 can generate an illumination beam 106 with high coherence (e.g., high spatial coherence and / or temporal coherence). For example, illumination source 104 may include one or more broadband lasers, such as (but not limited to) one or more supercontinuum lasers or white light lasers. By another example, illumination source 104 may include one or more narrowband lasers. By a further example, illumination source 104 may include one or more tunable lasers for providing an illumination beam 106 with tunable spectral intensity. Furthermore, coherent illumination source 104 can be based on any type of technology or product design. For example, illumination source 104 may include (but is not limited to) any combination of one or more fiber lasers, one or more diode lasers, or one or more gas lasers.

[0041] 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). By another example, the illumination source 104 may include a laser-supplied plasma (LSP) source, such as (but not limited to) an LSP lamp, LSP bulb, or LSP chamber adapted to house one or more elements capable of emitting broadband illumination when excited into a plasma state by a laser source. By another example, the illumination source 104 may include a lamp source, such as (but not limited to) an arc lamp, discharge lamp, electrodeless lamp, or the like.

[0042] Furthermore, the illumination source 104 may comprise 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.

[0043] The illumination source 104 may 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 may include one or more mode-locked lasers, one or more Q-switched lasers, or the like.

[0044] 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 adapted to modify and / or adjust 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.

[0045] In another embodiment, the scanning metrology system 100 includes an objective lens 126 for focusing an illumination beam 106 onto a sample 102.

[0046] Sample radiation 112 may comprise any type of radiation emitted from sample 102, including (but not limited to) light or particles. For example, sample radiation 112 may comprise a portion of the illumination beam 106 reflected and / or scattered by sample 102. By another example, sample radiation 112 may comprise luminescence induced by the absorption of illumination beam 106 by sample 102. By another example, sample radiation 112 may comprise particles from sample 102 in response to illumination beam 106, such as (but not limited to) backscattered electrons or secondary electrons.

[0047] 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 adapted to modify and / or adjust 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.

[0048] In another embodiment, the scanning metrology system 100 includes a beam splitter 132. For example, as... Figure 1 As described, beam splitter 132 may be shared by both illumination path 108 and collection path 110, such that objective lens 126 can both guide illumination beam 106 to sample 102 and collect sample radiation 112. In another embodiment, although not shown, illumination path 108 and collection path 110 may include splitting lenses for guiding illumination beam 106 to sample 102 and collecting sample radiation 112, respectively.

[0049] Detector 114 may comprise any optical detector known in the art suitable for capturing sample radiation 112 received from sample 102. In one embodiment, detector 114 comprises a multi-pixel detector suitable for capturing one or more images. For example, detector 114 may comprise (but is not limited to) a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) device. Detector 114 may be positioned at any imaging plane of the scanning metrology system 100. For example, detector 114 may be positioned at a plane conjugate to sample 102 to generate an image of sample 102. In another example, detector 114 may be positioned at a pupil plane (or its conjugate) to generate a pupil image.

[0050] Furthermore, the scanning metrology system 100 may include a plurality of detectors 114 (e.g., associated with a plurality of beam paths generated by one or more beam splitters to facilitate a plurality of metrological measurements (e.g., a plurality of metrological instruments) through the scanning metrology system 100). In another embodiment, the detectors 114 may include spectral detectors adapted to identify wavelengths of radiation emitted from the sample 102.

[0051] In another embodiment, the scanning metrology system 100 includes a scanning subsystem for scanning the sample 102 relative to the measurement field during metrological measurements. In one embodiment, such as Figure 1 As described herein, the scanning subsystem includes a sample stage 134 for fixing 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 focusing 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) linear translation stages, rotation stages, or tilt / tilt stages. In another embodiment, although not shown, the scanning subsystem includes one or more beam scanning optics (e.g., rotatable mirrors, galvanometers, or the like) for scanning the illumination beam 106 relative to the sample 102.

[0052] Detector 114 can be configured to generate metering signals (e.g., sample plane and / or pupil plane images) during scanning using any technique known in the art. In one embodiment, detector 114 comprises a 2D pixel array having a capture time and / or refresh rate sufficient to capture one or more images within selected image tolerances (e.g., image blur, contrast, sharpness, or the like) during scanning. In another embodiment, detector 114 comprises a line scan detector that continuously generates images one pixel at a time. In yet another embodiment, detector 114 comprises a time delay integration (TDI) detector. The TDI detector generates continuous images of sample 102 when the motion of sample 102 is synchronized to a charge transfer clock signal in the TDI detector. Specifically, the TDI detector acquires charge from exposure on pixel rows and includes clock pulses that transfer charge between adjacent pixel rows along the scan direction. As the motion of sample 102 along the scan direction is synchronized to charge transfer in the TDI detector, charge continuously accumulates during scanning. This process continues until the charge reaches the last pixel row and is subsequently read out from the detector. In this way, images of the object are accumulated over a longer frame period compared to the possible scenarios using a simple line-scan camera. This relatively longer acquisition time reduces the level of photon noise in the image. Furthermore, the synchronized movement of the image and charge prevents blurring in the recorded image.

[0053] For reference Figure 2 Section 4 provides a more detailed description of the design of various measurement objectives.

[0054] Figure 2 This is a top view of a static metrological target 202 suitable for static mode (e.g., frame mode) metrological measurements in which sample 102 is stationary during measurement, according to one or more embodiments of this disclosure.

[0055] For example, Figure 2 The static metrology target 202 can be applied to overlap metrology used to determine the registration error between two layers of sample 102. Specifically, the static metrology target 202 may comprise four units 204a to 204d of a quadrant denoted herein as static metrology target 202. Each unit 204a to 204d may comprise a first layer printed element 206 positioned on a first layer of sample 102 and a second layer printed element 208 positioned on a second layer of sample 102.

[0056] Furthermore, units 204a and 204d can be configured to provide, for example... Figure 2The overlap measurement along the X-direction is described herein. For example, the overlap measurement along the X-direction can be performed by directly comparing the relative positions of the first layer printed element 206 and the second layer printed element 208 within each cell or between cells 204a and 204d. In another example, the overlap measurement along the X-direction can be performed by comparing the rotationally symmetric (e.g., rotationally symmetric, reflection symmetric, mirror symmetric, or similar) points between the first layer printed elements 206 distributed across cells 204a and 204d with the symmetric points between the second layer printed elements 208 distributed across cells 204a and 204d. Similarly, cells 204b and 204c can be configured to provide, as described above, the overlap measurement along the X-direction can be performed by comparing the relative positions of the first layer printed elements 206 and the second layer printed elements 208 distributed across cells 204a and 204d. Figure 2 The overlapping measurement along the Y direction is described in the figure.

[0057] It should be understood herein that a metrology tool configured for static measurements (e.g., MAM operating mode) can capture an image of the static metrology target 202 within a single measurement field of view 210 (e.g., a single frame). Therefore, the effect of time-varying errors in the metrology tool on metrology measurements is generally limited to time-varying errors occurring within a time frame approximately the exposure time required to generate an image of the complete static metrology target 202. Furthermore, because all units 204a to 204d are imaged simultaneously in a single image, any time-varying errors will have a common effect on various portions of said image. In this respect, time-varying errors generally do not typically introduce differences between portions of the image associated with unit 204a (or unit 204b) and portions of the image associated with unit 204d (or unit 204c).

[0058] However, it should be further understood in this paper that the scanning metrology system 100 configured for scanning measurements can generate an image of the static metrological target 202 line by line as the sample 102 is translated through the measurement field. Therefore, time-varying errors can introduce differences that can directly affect the overlapping metrological measurements between portions of the image associated with cell 204a (or cell 204b) and portions of the image associated with cell 204d (or cell 204c).

[0059] For reference Figures 3 to 5 This describes a metrological target suitable for scanning mode measurement according to one or more embodiments of the present disclosure.

[0060] Figure 3 This is a conceptual diagram of a scanning measurement target 302 according to one or more embodiments of the present disclosure.

[0061] In one embodiment, the scanning metrology target 302 includes a plurality of measurement units 304 distributed on the sample 102, wherein each unit 304 includes printed elements on one or more layers of the sample 102 designed to provide selected metrological measurements. For example, overlay metrology can utilize the relative positions of patterned elements on two or more layers of the sample 102 to determine the registration error of associated layers during photolithography, wherein the patterned elements are positioned in one or more units 304 of the scanning metrology target 302. By another example, the unit 304 may include printed elements on one or more sample layers, wherein characteristics such as (but not limited to) size, critical dimension (CD), or position indicate one or more process parameters during exposure (e.g., focal position of the sample 102, illumination dose, or the like).

[0062] In another embodiment, the units 304 in the scanning measurement target 302 are organized within one or more measurement groups 306 distributed 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 units 304 distributed along a lateral direction 310 orthogonal to the scanning direction 308, and the scanning measurement target 302 may contain any number of measurement groups 306 along the scanning direction 308.

[0063] It should be understood throughout this document that the scan metrology system 100 may have multiple associated error sources that can negatively impact metrological performance. Specifically, because the scan metrology system 100 generates a continuous image along a scan, the effects of time-varying errors (e.g., but not limited to, vibration or jitter) can manifest as variations in a particular portion of the continuous image relative to other portions (e.g., spatial variations within the continuous image). For example, an error associated with the scan direction 308 can cause a lateral displacement of a particular portion of the continuous image along the transverse direction. By another example, an error associated with the translational velocity (e.g., scan speed) along the scan direction 308 can manifest as stretching or compression of portions of the continuous image.

[0064] In the context of metrology, spatial variations in consecutive images caused by system-induced errors can negatively impact the performance of metrology algorithms designed to extract information about samples from images. For example, overlap metrology can measure registration errors between sample layers based on the relative positions of imaging features on two or more layers of sample 102. However, spatial variations in the image can directly affect the position of features in the image and thus directly contribute to measurement errors. As another example, critical size metrology can measure feature sizes on a sample based on the size of features in the image. However, spatial variations in the image can directly affect the imaged size of features at different locations along the scan direction 308 and thus directly contribute to inconsistent measurement results along the scan direction 308.

[0065] Therefore, in embodiments of this disclosure, the cell 304 associated with the common measurement may be arranged to be positioned within the common measurement group 306. In this respect, cells 304 within each measurement group 306 may be measured simultaneously to mitigate the effects of time-varying errors. It should be understood herein that time-varying errors can still affect cells 304 within each measurement group 306. However, only time-varying errors occur on a timescale approximately equal to the measurement time of the measurement group 306 (e.g., approximately the size of the largest cell 304 measured along the scan direction 308). Furthermore, errors occurring even on this timescale will similarly affect all cells 304 in the measurement group 306.

[0066] However, it should be understood that the metrology algorithm may utilize units 304 in different measurement groups 306. This paper only considers the effect of increasing the size of the portion of the image along the analyzed scan direction 308, which could increase time-varying errors.

[0067] The scanning measurement target 302 may include any selected number of measurement groups 306, each measurement group 306 containing any number of units 304 suitable for any selected measurement. In one embodiment, the scanning measurement target 302 may include a first measurement group 306 having one or more units 304 designed to provide overlapping measurements along a first direction (e.g., the X direction), and a second measurement group 306 having one or more units 304 designed to provide overlapping measurements along a second direction (e.g., the Y direction). In this respect, units 304 in the first measurement group 306 associated with overlapping measurements along the first direction can be measured simultaneously to provide accurate measurement data. Similarly, units 304 in the second measurement group 306 associated with overlapping measurements along the second direction can be measured simultaneously. In another embodiment, the scanning measurement target 302 may include one or more units 304 in a common measurement group 306 designed to provide overlapping measurements along multiple directions (e.g., the X and Y directions). In this respect, units 304 in the common measurement group 306 associated with overlapping measurements along said multiple directions can be measured simultaneously. In another embodiment, the scan metrology target 302 may include one or more units 304 designed to provide CD metrology in the common measurement group 306 to minimize or otherwise mitigate the impact of time-varying errors on CD measurements for features at different locations within the scan metrology target 302. In another embodiment, the scan metrology target 302 may include one or more units 304 designed to provide process metrology data (e.g., illumination dose, focal position, or the like in a lithography tool) in the common measurement group 306 to minimize or otherwise mitigate the impact of time-varying errors on process metrology measurements. Therefore, it should be understood that examples of a specific number or layout of measurement groups 306 within the scan metrology target 302 are provided for illustrative purposes only and should not be construed as limiting.

[0068] In one embodiment, the scanning metrology target 302 includes one or more measurement groups 306, wherein various measurement groups 306 within each measurement group 306 provide metrological measurements associated with a common direction on the sample 102 (e.g., overlap, process monitoring, or the like). For example, the scanning metrology target 302 may include: a first measurement group 306, which may include units 304 providing metrological measurements along a first direction; and a second measurement group 306, which may include units 304 providing metrological measurements along a second direction different from the first direction. The first direction and the second direction may be, but are not necessarily, orthogonal. Further, the first direction and the second direction may correspond to (but are not necessarily) the scanning direction 308 and the lateral direction 310.

[0069] Furthermore, the measurement group 306 may include a unit 304 having printed elements with any selected pattern suitable for providing a selected measurement of interest. In one embodiment, the measurement group 306 includes at least one unit 304 having periodic printed elements. For example, the periodic printed elements may include a plurality (e.g., three or more) of elements having the same spacing along a selected direction. Further, the plurality of elements may have (but do not necessarily have) the same size.

[0070] For reference Figures 4A to 5 This describes various configurations of the scanning metrology target 302 according to one or more embodiments of the present disclosure. For example, it is considered herein that overlap can be designed to provide overlapping measurements based on any measurement algorithm known in the art. For example, overlapping measurements along the measurement direction can be generated by directly comparing the relative positions of printed elements generated using different exposure steps with symmetrical (e.g., rotational symmetry, reflection symmetry, or the like) points. Furthermore, although Figures 4A to 5 The scanning metrology target 302 described herein is configured for overlapping metrology, but it should be understood that the scanning metrology target 302 configured according to this disclosure is not limited to overlapping metrology. Therefore, those skilled in the art can extend the features and operating principles described in the illustrated embodiments to designs of additional metrology targets, taking into account the context herein.

[0071] Figure 4A This is a top view of a scanning measurement target 302 having two measurement groups 306a, 306b for overlapping measurement along orthogonal directions, according to one or more embodiments of the present disclosure, wherein the cells 304 within each of the two measurement groups 306a, 306b exhibit rotational symmetry.

[0072] In one embodiment, the scanning measurement target 302 includes: a first measurement group 306a comprising a first unit 304a and a second unit 304b distributed along a lateral direction 310; and a second measurement group 306b comprising a third unit 304c and a fourth unit 304d distributed along a lateral direction 310. The second measurement group 306b is separated from the first measurement group 306a along a scanning direction 308. Further, units 304a to 304d are depicted 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 processing steps. For example, the first set of printed elements 402 can be manufactured on a first layer of the sample 102, and the second set of printed elements 404 can be manufactured on a second layer of the sample. By 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 the sample 102 in different processing steps.

[0073] Furthermore, any of units 304a to 304d may include unit 304 having printed elements with any selected pattern suitable for providing a selected measurement of interest. For example, measurement groups 306a and / or 306b may include at least unit 304 having periodic printed elements. For example, periodic printed elements may include a plurality (e.g., three or more) of elements having the same spacing along a selected direction. Furthermore, the plurality of elements may have (but not necessarily) the same size.

[0074] In one embodiment, first units 304a and second units 304b in the first measurement group 306a are configured to provide overlapping measurements along a first direction (e.g., the X direction), while third units 304c and fourth units 304d in the second measurement group 306b are configured to provide overlapping measurements along a second direction (e.g., the Y direction). In this regard, first units 304a and second units 304b in the first measurement group 306a can be imaged simultaneously to minimize or otherwise mitigate the effect of time-varying errors on associated metrological measurements along the first direction. Similarly, third units 304c and fourth units 304d in the second measurement group 306b can also be imaged simultaneously to minimize or otherwise mitigate the effect of time-varying errors on associated metrological measurements along the second direction.

[0075] Furthermore, Figure 4A The scanning metrology target 302 is well-suited (but not limited to) for overlapping metrology based on the rotational symmetry of cell 304. For example, cell 304b can be designed to correspond to a 180-degree rotation of cell 304a without overlap error, such that overlapping measurements along the X-direction can be generated by comparing the rotational symmetry point 406 of the first group of printed elements 402 in measurement group 306a with the rotational symmetry point 408 of the second group of printed elements 404 in measurement group 306a. Figure 4A Similarly, cell 304d can be designed to correspond to a 180-degree rotation of cell 304c without overlap error, such that overlapping measurements along the Y direction can be generated by comparing the rotational symmetry point 410 of the first group of printed elements 402 in measurement group 306b with the rotational symmetry point 412 of the second group of printed elements 404 in measurement group 306b. In this respect, the measurement of the rotationally symmetric cell 304 can mitigate or otherwise reduce the rotational error of the scanning metrology system 100.

[0076] In this paper, various arrangements of elements within cell 304 of measurement group 306 are considered to provide the desired symmetry. Figure 4BThis is a top view of a scanning measurement target 302 having two measurement groups 306a, 306b for overlapping measurements along orthogonal directions, according to one or more embodiments of the present disclosure, wherein the cells 304 within each of the two measurement groups 306a, 306b exhibit rotational symmetry. Specifically, Figure 4B The units 304c and 304d in the measurement group 306b are distributed along the Y direction (e.g., the measurement direction) relative to Figure 4A The scanning measurement target 302 in the middle increases the length of the measurement group 306b along the Y direction.

[0077] Furthermore, this paper considers that the scanning measurement target 302 can be adapted for scanning in multiple directions, which can help compare measurements taken with a common target along different directions. For example, scanning can be performed along the X direction. Figure 4B The scanning measurement target 302 in the middle (e.g., such as Figure 4B The scanning direction 308 and the transverse direction 310 shown in the figure are interchangeable.

[0078] However, it should be understood that Figure 4A and 4B The 180-degree rotational symmetry described herein is provided for illustrative purposes only and should not be construed as limiting. Specifically, the scanning measurement target 302 (or unit 304 of any group in measurement group 306) may correspond to a version rotated relative to each other by any amount (e.g., 45 degrees, 90 degrees, or the like).

[0079] Furthermore, as previously described herein, the element 304 in measurement group 306 does not need to have any rotational symmetry.

[0080] In another embodiment, measurement group 306 comprises a plurality of identical units 304. Figure 4C This is a top view of a scanning metrology target 302 having multiple identical units 304c, 304d according to one or more embodiments of the present disclosure. Therefore, overlapping measurements along the Y direction can be generated by performing overlap measurements individually on units 304c and 304d (e.g., based on the relative positions and / or symmetry points of the first group of printed elements 402 and the second group of printed elements 404 in units 304c and 304d, respectively) and then averaging the individual measurements to eliminate rotational errors of the scanning metrology system 100.

[0081] In another embodiment, the measurement group 306 includes one or more pairs of units 304 designed to have a reflection symmetry (e.g., mirror symmetry, 1-D symmetry, or the like) along the direction to be measured (e.g., the X direction, Y direction, or the like). Figure 4DThis is a top view of a scanning metrology target 302 having two measurement groups 306a, 306b according to one or more embodiments of the present disclosure, wherein the cells 304 within each of the two measurement groups 306a, 306b exhibit reflective symmetry. For example, the first set of printed elements 402 and the second set of printed elements 404 in measurement group 306a may be designed to be symmetrical about axis 414, such that overlapping 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 with 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 measurement group 306b may be designed to be symmetrical about axis 416, such that overlapping measurements along the Y direction can be associated with a comparison of the axis of symmetry of the first set of printed elements 402 in measurement group 306b with the axis of symmetry of the second set of printed elements 404 in measurement group 306b.

[0082] In another embodiment, measurement group 306 comprises multiple units 304 of printed elements (e.g., a first group of printed elements 402 and a second group of printed elements 404) that provide the same metrological measurements but have different layouts. For example, the printed elements in unit 304 may include variations in spacing between elements, segmentation of elements, element asymmetry, or the like. In this regard, the metrological signals associated with the multiple units 304 can be used to monitor process errors and / or pattern placement errors (PPE), where variations in the printed elements are sensitive to process errors.

[0083] In another embodiment, a particular unit 304 may include patterned elements (e.g., gratings or the like) with intentionally inserted skew (e.g., offset). In this respect, the metrological measurements of unit 304 can be used to provide residual minimization via algorithms and / or flags.

[0084] However, it should be understood that Figures 4A to 4D The description of measurement groups 306, each having two units 304, is provided for illustrative purposes only and should not be construed as limiting. Measurement groups 306 of scanning measurement targets 302 may contain any number of units 304.

[0085] Figure 5 This is a top view of a scanning measurement target 302 according to one or more embodiments of the present disclosure, having two unit groups 306, each having three units 304 for overlapping measurements along orthogonal directions. For example, the scanning measurement target 302 may include a first measurement group 306a having units 304a to 304c and a second measurement group 306b having units 304d to 304f. Further, as... Figure 5As illustrated, the symmetry between units 304 can vary between different measurement groups 306. For example, the first measurement group 306a contains units 304 with two rotational variants, while the second measurement group 306b contains the same units 304.

[0086] The objects described herein sometimes refer to different components contained within or connected to other components. It should be understood that such depicted architectures are merely exemplary, and many other architectures can actually be implemented to achieve the same functionality. Conceptually, any arrangement of components achieving the same functionality is effectively “associated” to achieve the desired functionality. Therefore, any two components in this document combined to achieve a particular functionality can be considered “associated” with each other to achieve the desired functionality, regardless of the architecture or intermediate components. Similarly, any two such associated components can also be considered “connected” or “coupled” to each other to achieve the desired functionality, and any two components that can be suchly associated can also be considered “coupled” to each other to achieve the desired functionality. Specific examples of couplerability include (but are not limited to): physically interactive and / or physically interactive components, and / or wirelessly interactive and / or wirelessly interactive components, and / or logically interactive and / or logically interactive components.

[0087] It is believed that this disclosure and its many accompanying advantages will be understood from the foregoing description, and it will be appreciated that various changes in the form, construction, and arrangement of the components can be made without departing from the subject matter of the disclosure or sacrificing all its substantial advantages. The forms described are merely illustrative and the appended claims are intended to cover and encompass such changes. Furthermore, it should be understood that the invention is defined only by the appended claims.

Claims

1. A measurement target, comprising: A first measurement group comprising a first set of two or more units distributed and aligned along a lateral direction on a sample, wherein the first set of two or more units are arranged in a row along the lateral direction and configured to be simultaneously measured during scanning by a scanning metrology tool along a scanning direction, wherein the lateral direction on the sample is orthogonal to the scanning direction, wherein the first set of two or more units in the first measurement group exclusively includes a grating structure having a periodicity along a first direction, wherein the first set of two or more units in the first measurement group are configured to provide at least a first metrological measurement associated with the first direction when characterized by the scanning metrology tool during scanning along the scanning direction, wherein the distribution of the first set of two or more units in the first measurement group along the lateral direction provides a time-varying error common to the first set of two or more units associated with the first metrological measurement; and A second measurement group comprising a second set of two or more units distributed and aligned along the lateral direction on the sample, wherein the second set of two or more units are arranged in a row along the lateral direction and configured to be measured simultaneously during scanning by the scanning metrology tool along the scanning direction, wherein the second measurement group is separate from the first measurement group along the scanning direction, wherein the second set of two or more units in the second measurement group exclusively includes a periodic grating structure along a second direction different from the first direction, wherein the second set of two or more units in the second measurement group is configured to provide at least a second metrological measurement associated with the second direction when characterized by the scanning metrology tool during scanning along the scanning direction, wherein the distribution of the second set of two or more units in the second measurement group along the lateral direction provides a time-varying error common to the second set of two or more units associated with the second metrological measurement.

2. The measurement target according to claim 1, comprising: One or more additional measurement groups, each additional measurement group comprising two or more units distributed along the lateral direction on the sample, the one or more additional measurement groups being separate from the first measurement group and the second measurement group along the scan direction, wherein the two or more units in each of the one or more additional measurement groups are configured to provide at least one or more additional metrological measurements when characterized by the scan metrology tool during scanning along the scan direction, wherein the distribution of the two or more units in each of the one or more additional measurement groups along the lateral direction provides a time-varying error common to the one or more additional measurement groups and associated with the one or more additional metrological measurements.

3. The metrological target according to claim 1, wherein the first metrological measurement includes: Overlapping metrological measurements along the first direction on the sample, wherein the second metrological measurement includes: Overlapping measurement along a second direction on the sample that is different from the first direction.

4. The measurement target of claim 3, wherein the overlap measurement along the first direction on the sample is based on the relative positions of the grating structures in two or more units of the first group of the first measurement group, and wherein the overlap measurement along the second direction on the sample is based on the relative positions of the grating structures in two or more units of the second group of the second measurement group.

5. The measurement target of claim 3, wherein the overlapping measurement along the first direction on the sample is based on the relative position of the rotational symmetry center of the grating structure in the first measurement group, and wherein the overlapping measurement along the second direction on the sample is based on the relative position of the rotational symmetry center of the grating structure in the second measurement group.

6. The measurement target of claim 3, wherein the overlap measurement along the first direction on the sample is based on the relative position of the reflection symmetry axis of the grating structure in the first measurement group, and wherein the overlap measurement along the second direction on the sample is based on the relative position of the reflection symmetry axis of the grating structure in the second measurement group.

7. The measurement target according to claim 1, wherein at least one of the first group of two or more units or the second group of two or more units comprises two or more identical units.

8. The measurement target according to claim 1, wherein at least one of the first measurement group or the second measurement group comprises a unit having a set of periodically printed elements.

9. The metrological objective according to claim 1, wherein at least one of the first metrological measurement or the second metrological measurement comprises: Process parameters of the lithography tool used in manufacturing one or more layers of the sample.

10. The measurement target according to claim 9, wherein the process parameters include: At least one of the focal position of the sample or the illumination dose on the sample when any one of the one or more layers of the sample is exposed in the photolithography tool.

11. The metrological objective according to claim 1, wherein at least one of the first metrological measurement or the second metrological measurement comprises: At least one of the following: overlapping measurement, critical dimension measurement, or sidewall angle measurement.

12. The metrological objective according to claim 1, wherein at least one of the first metrological measurement or the second metrological measurement comprises: At least one of the size, position, or orientation of one or more printed elements on the sample.

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