High throughput optical metrology

Abstract

This application relates to high-throughput optical metrology. A method for optically metrologically measuring a sample is provided, the method comprising illuminating a region of the sample with multiple sets of pulses of different wavelengths during variable-speed movement of the sample; collecting light reflected from the sample as a result of the illumination to provide multiple sets of frames, each set of frames comprising multiple partially overlapping frames associated with different wavelengths; and processing these frames to provide an optical metrological result indicating one or more evaluation parameters of elements of the sample region; wherein the processing is based on a mapping between the multiple sets of frames and reference measurements obtained through other optical metrological processes that exhibit a higher spectral resolution than that obtained by illumination and collection.

Description

[0001] This application is a divisional application of the PCT application entitled "High Throughput Optical Metrology", filed on August 27, 2021, with application number 202180073458.8, which entered the national phase in China. The international application number of the PCT application is PCT / IB2021 / 057862, and the date of entry into the national phase of the PCT application is April 26, 2023. Technical Field

[0002] This application relates to high-throughput optical metrology. Background Technology

[0003] Optical metrology for semiconductor devices is a standard method for measuring critical dimensions on semiconductor wafers to facilitate high throughput in semiconductor manufacturing processes. Several optical metrology-based techniques, such as spectral reflectance measurement, scattering measurement, ellipsometric measurement, and spectral ellipsometric measurement, are commonly used to detect critical dimensions, film thickness, composition, and other parameters of semiconductor wafers during manufacturing.

[0004] White light reflectance measurement, scattering measurement, and ellipsometric measurement are relatively time-consuming techniques because they require acquiring and processing spectral information at hundreds or even thousands of wavelengths. Therefore, measurements are performed at selected sites that may constitute only a negligible portion of the wafer.

[0005] The measurement site size used in this technology is typically less than 100 μm, the measurements are performed sequentially site by site, and only a very limited number of measurement points can be performed without significantly impacting the throughput of the metrology system.

[0006] Hyperspectral imaging is a known optical metrology method. The wafer under test is illuminated with a broad spectrum, and the generated image data represents the intensity of light reflected or scattered from the wafer. Detected image pixels are individually analyzed across various spectral ranges. Hyperspectral imaging is expensive and complex. It requires high-speed computing, highly sensitive detectors, and substantial data storage resources to analyze hyperspectral data.

[0007] Scattering measurement tools are widely used in process control during semiconductor manufacturing. These tools typically measure reflectance spectra at certain test sites, and / or memory arrays, and / or other predetermined on-chip locations. The size of the area on the sample being measured (the area that reflects the detected light) or the spot size is usually very small, ranging in diameter from approximately 10 to 50 micrometers.

[0008] Scattering measurement tools are fast: for standard sampling schemes, MAM times can be well below seconds, and TPT times are typically above 100W / hour. Increasing the sampling scheme will require measuring more sites, but in any case, using small spot sizes to measure large areas for WID and / or WIW, and / or if the focus is on spatial wafer mapping or extreme wafer edge performance, uniformity may be an issue.

[0009] Several known methods exist for providing full-wafer images / graphs, such as by imaging the entire wafer "at once" (e.g., Spark Nanda technology, Lars Markwort et al., "Full wafer macro-CD imaging for excursion control of fast patterning processes", Proc. SPIE Vol. 7638, 2010) or by using scanning (US Patent Application US 2019 / 0244374 A1). These tools utilize spectral filters or RGB cameras and analyze wafer images based on DOE wafers (particularly DOE wafers prepared in advance to define the correlation between the image and the parameters of interest). It is suggested that scanning tools be used as part of a polishing apparatus to allow wafer images to be closely approximated during the fabrication process.

[0010] The concept of Integrated Metrology (IM) is described in detail in Nova's patents US6752689, US9,184,102, etc. The Measurement Unit (MU) of an IM is typically attached to the Equipment Front-End Module (EFEM) of the processing tool, and the wafer is transferred to the IM system via a robot on the EFEM for measurement. A standard measurement sequence may include global and fine alignment of the wafer using an imaging system, as described in Nova's US patents US5682242, US6752689, etc.

[0011] We are very keen to provide a full wafer metrology solution for optical metrology systems without any detrimental impact on throughput. Summary of the Invention

[0012] In one aspect, this application provides an optical metrology method for a sample, the method comprising: irradiating a region of the sample with multiple sets of pulses of different wavelengths during variable-speed movement of the sample; collecting light reflected from the sample as a result of the irradiation to provide multiple sets of frames, each set of frames comprising multiple partially overlapping frames associated with different wavelengths; and processing the frames to provide optical metrology results indicating one or more evaluation parameters of elements of the region of the sample; wherein the processing is based on a mapping between the multiple sets of frames and reference measurements obtained through other optical metrology processes, which exhibit a higher spectral resolution than those obtained through irradiation and collection.

[0013] On the other hand, this application provides an integrated metrology method, the method comprising: scanning a wafer with at least one illumination line via an illumination module of a first system during wafer movement; acquiring optical information about the wafer via the first system at a first spectral resolution, a first throughput, and during wafer movement between a metrology device and another device, wherein the first spectral resolution is coarser than a second spectral resolution of a second system, wherein the first throughput exceeds the second throughput of the second system; and measuring characteristics of the wafer via the first system.

[0014] On the other hand, this application provides an integrated metrology method, the method comprising: acquiring optical information related to a wafer via processing circuitry, the image being generated by a first system and having a first spectral resolution, the acquisition of the optical information being performed at a first throughput and during wafer movement between a second system and another device; acquiring second system results related to one or more regions of the wafer via processing circuitry, wherein the metrology results are generated by the second system, the second system being configurable to measure features within the regions of the wafer at a second spectral resolution finer than the first spectral resolution and at a second throughput lower than the first throughput; and estimating metrology results related to one or more additional regions of the wafer based on (a) a mapping between the first system results and the second system results, (b) the first system results, and (c) the second system results. Attached Figure Description

[0015] The subject matter considered to be the present invention is specifically identified and explicitly stated in the concluding section of the specification. However, aspects of the organization and operation of the invention, as well as its objectives, features, and advantages, can be best understood by referring to the following detailed description when read in conjunction with the accompanying drawings, wherein: Figure 1 An example of a frame is shown; Figure 2 An example of a lighting element is shown; Figure 3 An example of an optical metrology system and its environment is shown; Figure 4 An example of an optical metrology system and its environment is shown; Figure 5 An example of an optical metrology system and its environment is shown; Figure 6 An example of the components of an optical metrology system is shown; Figure 7 An example of a wafer, a camera, and the camera's effective field of view is shown; Figure 8 An example of a wafer, a camera, and the camera's effective field of view is shown; Figure 9 Examples of components and frames of an optical metrology system are shown; Figure 10 An example of the components of an optical metrology system is shown; Figure 11 An example of the method is shown; Figure 12 At least a portion of the system is shown; Figure 13 At least a portion of the system is shown; Figure 14 The image is shown; Figure 15 At least a portion of the system is shown; Figure 16 An example of the method is shown; and Figure 17 An example of the method is shown. Detailed Implementation

[0016] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, those skilled in the art will understand that the invention can be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail to avoid obscuring the invention.

[0017] Understandably, for the sake of simplicity and clarity, the elements shown in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to others for clarity. Furthermore, reference figures may be repeated across figures where deemed appropriate to indicate corresponding or similar elements.

[0018] Since the illustrative embodiments of the present invention can be implemented in most cases using electronic components and circuits known to those skilled in the art, details will not be explained in a broader scope than that deemed necessary above in order to understand and appreciate the basic concepts of the invention and to avoid obscuring or departing from the teachings of the invention.

[0019] Any reference to the method in this specification shall be applied mutatis mutandis to systems capable of performing the method, and shall also be applied mutatis mutandis to non-transitory computer-readable media storing instructions that, once executed by a computer, would cause the method to be performed.

[0020] Any reference to the system in the specification shall be interpreted in accordance with the methods that can be executed by the system, and shall be interpreted in accordance with the non-transitory computer-readable medium storing instructions that, once executed by a computer, would cause the execution of the method.

[0021] The following text may refer to wafers. Wafers (especially semiconductor wafers) are merely examples of samples.

[0022] The following text refers to full wafer scanning. It should be noted that any reference to full scanning may be applied by analogy to scanning only one or more portions of the wafer.

[0023] The following text may refer to light-emitting diodes (LEDs). This is merely an example of an illumination source.

[0024] The following text refers to wavelengths. Any reference to wavelengths shall apply mutatis mutandis to a range of wavelengths. Additionally or alternatively, any reference to wavelengths may apply mutatis mutandis to any other property of illumination and / or collection—e.g., polarization, the angular content of the illumination or / or collection beam, etc.

[0025] The following text may refer to the effective field of view (FOV). The effective FOV is the FOV considered during metrology. The effective FOV can be the entire FOV of a region scan camera or a portion of the FOV. For example, if only a portion of the camera pixels form the area of ​​interest processed for metrology, then the effective FOV is limited to that portion of pixels.

[0026] A very fast (e.g., within 0.5 seconds, 1 second, or 2 seconds) full wafer scanning metrology system is provided, which may include: a. An illumination module that uses pulses of light from an illumination element such as an LED to illuminate an area on the wafer—known as the region of interest (ROI). These pulses have different wavelengths (one after another), with each wavelength illuminating the corresponding ROI during setup and metering sessions.

[0027] b. One or more area scanning cameras with a narrow and elongated effective field of view (FOV). One or more cameras provide low-resolution spectral information about the sample—because the spectral information is limited by the illumination wavelength.

[0028] c. One or more additional optical elements. For example, lenses, objectives, light guides, beam splitters, etc.

[0029] A frame is obtained from the relevant wafer region when the last wafer region is illuminated with light of different wavelengths (at different times).

[0030] Illumination can be performed outside the chamber (MU) and / or when the wafer moves from one chamber and / or tool to another chamber and / or tool. Examples of such movement may include the movement of the wafer from a processing tool (e.g., a CMP polisher) to a metrology tool, or from a metrology tool to a polisher, the movement of the wafer from or to a housing, and so on.

[0031] Wafers can be moved by EFEM robots or by any other means.

[0032] The robot's movement can exhibit speed variations—the opposite of the platform's constant-speed movement. The robot's movement may not be controlled by the optical metrology system. The maximum movement speed of the wafer should be known or estimated.

[0033] The effective FOV is narrow and elongated. The number of pixel rows (the width of the effective FOV, the narrow dimension) is a trade-off between the number of possible wavelengths available in a metrology session (e.g., at least 5, 8, 10, 15, 20, 25, 30, 35) and the intensity of reflected light—because a larger effective FOV would require illuminating a larger area of ​​the wafer—and could reduce illumination energy density.

[0034] Successive frames at different wavelengths are overlapped, which provides complete wafer image coverage at any different scanning wavelength. Overlapping allows this method to acquire visual information about any point of interest on the wafer.

[0035] You can select any optical parameters—such as wavelength, polarization, etc.

[0036] Optical parameters can be selected based on the metrological parameters to be evaluated (of the wafer or any part thereof). Metrological parameters can refer to one or more structural elements (e.g., one or more submicron structural elements, one or more nanometer-scale structural elements, one or more submicron regions of a bare wafer), and can refer to one or more properties of one or more structural elements (e.g., critical dimensions, film thickness, composition, etc.).

[0037] When applied to one or more structural elements, one or more optical parameters are selected based on model-based simulations of the optical process of irradiating a sample, collecting radiation from the sample, and generating a detection signal. The model-based simulations reveal one or more optical parameters that, once applied, provide results (e.g., the most sensitive) for the metrological parameters of one or more tests.

[0038] Optical parameters (such as wavelength) can be selected from a large set of parameters available from the system.

[0039] It should be noted that the spectral resolution of optical metrology methods is coarser than that of spectral reflectance measurement methods because it measures signals generated by illumination through a limited number of wavelengths, and each wavelength represents a narrow spectral range when illuminated by LEDs.

[0040] Assume the optical parameters include six different wavelengths that can be emitted from one or more groups of six LEDs.

[0041] refer to Figure 1 —— Figure 1 Seven frames 91-97 are shown. The first six frames 91-96 constitute a set of frames, which consists of six frames 91-96, obtained as a result of illuminating the wafer with six different illumination wavelengths. The seventh frame 97 represents the beginning of the next set of six frames—and is obtained as a result of illuminating the wafer with the first wavelength of the set of six different illumination wavelengths.

[0042] The LED pulses are timed sequentially to provide overlapping frames. It should be noted that... Figure 1 The image shows the overlap obtained at the robot's constant and maximum speed (scanning speed). In reality, however, the speed may vary over time and within a metering session. Lower speeds would result in greater overlap between frames.

[0043] exist Figure 1 In this process, the distance between pulses can be predetermined and is equal to, for example, 1 / 8 of the FOV (field of view in the scanning direction) divided by the maximum scanning speed.

[0044] Figure 2 A linear array of lighting elements 112 (which may be LEDs) is shown. It also shows four groups of six LEDs (for emitting six different wavelengths). Figure 2 Three groups of eight LEDs (forming an emission of eight different wavelengths) are also shown. It should be noted that any arrangement of LEDs can be provided.

[0045] In this scenario, after six strobe pulses, the LED will turn on again when the first wavelength illuminates the wafer, and the overlap between frames 91 and 97 will be 2 / 8 of the field of view (if the scan rate remains constant and equal to the maximum scan rate).

[0046] Due to variations in robot speed, the overlap between related frames differs, necessitating compensation for these varying overlaps. These frames are correlated when acquired using illumination of the same wavelength.

[0047] It is necessary to generate a map of the entire wafer (each set of related frames), and this requires combining (stitching) the related frames to provide an illumination map for each wavelength.

[0048] The assembly requires determining the location of the wafer region imaged by each frame.

[0049] Stitching frames on a bare wafer is more difficult than stitching frames on a patterned wafer. Wafer patterns can include anchor points that can be used to determine the position of each frame. In the case of a bare wafer, there may be no anchor points, and the edge of the wafer can be used to detect the region position of each frame. The position of the edge can be sensed by one or more cameras of an optical metrology system. Additionally or alternatively, other sensors can be used for edge detection and / or tracking wafer movement, for example, by tracking the position of a robot using visual or non-visual sensors.

[0050] Examples are provided where the effective FOV is smaller than the camera's full FOV, and it can include the use of a CMOS area sensor with ROI selection. Such an area sensor allows for the selection of a limited number of rows to capture an image, while the frame rate will be much higher than the full frame rate. For example, the Basler a2A1920-160umBAS camera: 1920 × 1200 pixels, 160 frames per second (fps), when used in 1920x40 pixel ROI mode (20 microsecond exposure), it operates at 2717 fps.

[0051] Assume the wafer moves at a constant speed of 0.5 m / s. The pixel size on the wafer is 50 micrometers. A lighting system with multiple LEDs can provide uniform illumination within an area 300 mm long and 2 mm wide.

[0052] To overlap the entire 300 mm length, four cameras were used, each imaging a 96 mm long area (1920 pixels for a Basler a2A1920-160umBAS camera) with some overlap, and 75 mm of non-overlap between each camera. The width was 2 mm and 40 pixels. The 300 mm scan took 0.6 seconds at a speed of 0.5 m / s.

[0053] The Basler a2A1920-160umBAS camera has a maximum frame rate of 1630 frames per second in 0.6 seconds.

[0054] From another perspective, each color of LED requires approximately 200 frames to achieve a 0.5 mm overlap (300 mm / 1.5 mm = 200 frames, 2 mm - 1.5 mm = 0.5 mm).

[0055] This means that a multi-region, multi-gated pulsed LED imaging system can be used to perform full-wafer mapping without reducing the scanning speed, employing eight different wavelengths (1600 frames / 200 frames per color = 8).

[0056] Figure 3 and Figure 4An example of the metrology system 40 and its environment is shown—for example, an IM tool 31 integrated with an EFEM 30 machining facility (CMP polisher). Other environments may be provided; for example, another environment may not include the IM tool 31.

[0057] The environment also includes a robot 60 (shown holding the wafer 99) and an IM tool 31 (or any other high-resolution optical metrology process, where high means higher than the process performed by the optical metrology system 40), the IM tool 31 having a chamber 35 configured to receive the wafer 99 from the robot, perform a high-resolution spectral reflectance measurement process, and then return the wafer to the robot.

[0058] The robot can place wafers into one or more foyer housings (FOUPs) 62, 63 and 64 of the EFEM 30, and / or provide wafers to another tool, such as a polisher 74.

[0059] Robot 60 can be part of the EFEM and can travel inside it. The housing and IM tools can be connected to the EFEM via ports / openings. The IM tools are typically connected via a six-bolt attachment, and the housing rests on a so-called load port that supports them. Metrology system 40 is mounted between the IM tools 31 and the EFEM. Metrology system 40 can be aligned along the Z-axis according to the Z-position of the robot arm (it can be configured to be partially or entirely adjustable during installation, for example, according to the Z-position of the wafer on the robot arm).

[0060] The optical metrology system 40 is positioned to perform metrology when the wafer is loaded onto the IM tool 31 by the robot 60 and / or when the wafer is unloaded from the IM tool 31.

[0061] The optical metrology system 40 may be an add-on system and its shape and size should be determined based on the dimensional constraints of other structural elements in its environment (e.g., configured to be mounted between the EFEM and the IM tool 31).

[0062] The metering system 40 can be configured as a "frame" surrounding the opening / port, with optics / illumination on its top portion—the connection between the IM tool and the EFEM is at least partially sealed. The metering system 40 can be connected to the control unit / computer of the IM tool 31, or an additional separate control unit / calculation of the metering system 40 can be housed inside or outside the IM tool.

[0063] Figure 5Examples of front and side views of the metrology system 40, the spectral reflectance measuring tool 31, and its chamber 35 are shown. The metrology system 40 is compact and can have dimensions much smaller than one meter (width and / or height and / or depth and / or extension beyond the spectral reflectance measuring tool). For example, the metrology system 40 can extend 5-15 cm (or more) beyond the spectral reflectance measuring tool, having a width and height of approximately 25-45 cm, etc. Figure 4 In some examples, at least a portion of the metrology system 40 is located within the spectral reflectance measurement tool 31.

[0064] The spectral reflectance measurement tool 31 can further process the results of the metrology system 40 for various purposes, such as calibration, verification, and selection of sites to be evaluated (where the results of the metrology system 40 may indicate problems, deviations from specifications, etc.).

[0065] Figure 6 Examples of some components of the optical metrology system 40 are shown.

[0066] The components include an LED-based lighting system 44, a beam splitter 43, a telecentric objective lens 42, and one or more cameras 41, such as a line scan camera or a region scan camera.

[0067] Telecentric objectives have vertical and horizontal sections.

[0068] LED 41 and beam splitter form a coaxial lighting system. The width and length of the beam splitter can be approximately 4 cm.

[0069] Light from LED 41 is directed by beam splitter 43 to wafer 99 (e.g., at a vertical angle of incidence), the light is reflected from wafer 99 to the vertical portion of telecentric lens 42, and then output from the horizontal portion of telecentric lens 42 to camera 44.

[0070] It should be noted that, although Figure 6 The example mentions telecentric objectives, but non-telecentric objectives (such as non-telecentric macro lenses) can also be used. This may require compensating for the non-uniformity of the illumination angle caused by using a non-telecentric objective.

[0071] Figure 7 and Figure 8 A sequence of five cameras 41(1)-41(5) is shown, which have narrow and elongated effective FOVs 42(1)-42(5) respectively, covering the entire length of wafer 99. Figure 8 A dedicated edge sensor 66 for detecting wafer edges is also shown. The edge sensor 66 can be linear and has a field of view whose length can exceed the wafer radius, and can be oriented (e.g., perpendicular to) the axis of movement of the wafer by the robot. The edge sensor can be positioned below the wafer and can utilize illumination from the main system.

[0072] Figure 9 Examples of some components of the optical metrology system 40 are shown. These components include an LED 55, a beam splitter 53, and an objective lens 52 having an input FOV wider than its output FOV. The objective lens 52 collects light from multiple illuminated segments 54(1), 54(2), and 54(3) extending along the entire width of the wafer 99 and directs the collected light to a camera 51 that is much narrower than the width of the wafer.

[0073] Figure 9 Also shown is a set of four frames 81(l)-81(4) and the first frame 81(5) of the next set of frames.

[0074] It should be noted that the metrology system 40 may use contact image sensors (CIS), which are positioned very close to the wafer, almost in direct contact with it. Examples of CIS sensors that may be used may include, for example, the VTCIS or VDCIS sensors from Tichawa Vision GmbH.

[0075] The wafer itself may not be perfectly flat, and the wafer may be moved by the robot along a path that may deviate from a purely horizontal path. To prevent physical contact between the wafer and the CIS (or any other optics of the metrology system 40), the metrology system 40 may be located at a safe distance from the wafer and / or the system may be moved according to the measured wafer movement and wafer flatness.

[0076] Figure 10 Examples of some components of the optical metrology system 40 are shown. These components may include an illumination element 105 (which may be located on a first plate 104), a lens 106, a beam splitter 107, a light guide 103, and a camera 102 that may be located on a second plate 101.

[0077] The metering system 40 may have a camera with pixels. A single camera pixel can “cover” a wafer area with a width / length in the micrometer range (e.g., 20, 40, 60 micrometers), and each row may include many pixels (e.g., for a full scan of a 300 mm wafer, and with a pixel width of 20 micrometers, there are 15,000 pixels per row).

[0078] It should be noted that the metrology parameters may change during a single scan of the wafer—for example, different metrology parameters may be applied to different parts of the wafer—for example, the scanning method for memory regions may differ from that for logic regions.

[0079] Furthermore, measurement parameters can be evaluated multiple times and can be changed, for example, to improve the sensitivity of the measurement process to changes in the value of the parameter being evaluated.

[0080] Figure 11 An example of an optical metrology method 200 for a sample is shown.

[0081] Method 200 may include steps 210, 220 and 230.

[0082] Step 210 may include irradiating a region of the sample with multiple sets of pulses of different wavelengths during the variable speed movement of the sample.

[0083] Step 220 may include collecting light reflected from the sample as a result of irradiation to provide multiple sets of frames, each set of frames including multiple partially overlapping frames associated with different wavelengths.

[0084] Step 230 may include processing these frames to provide optical metrology results indicating one or more evaluation parameters of elements in the sample region; wherein the processing is based on a mapping between multiple sets of frames and reference measurements obtained through other optical (or other reference) metrology processes that exhibit a higher spectral resolution than those obtained through illumination and collection.

[0085] Processing can be performed through a computerized system located in the metering system 40, the IM tool 31, and communicating with the metering system 40 and the IM tool.

[0086] Two systems (also referred to as units, modules, devices, or tools) are provided: a. The first system has a first spectral resolution (e.g., processing or detecting a first number of wavelengths of radiation) and a first throughput. It can provide information on a macroscopic scale.

[0087] b. The second system has a second spectral resolution (e.g., processing or detecting a second number of wavelengths of radiation) and a second throughput. It can provide information at the microscopic scale.

[0088] The first spectral resolution is lower than the second spectral resolution.

[0089] For example, while the first system can acquire and process optical information related to 8, 10, 15, 20 and up to tens (e.g., up to 30 or 40) wavelengths, the second system can acquire and process optical information related to 100 or even hundreds of wavelengths.

[0090] The first throughput exceeds the second throughput. For example, it exceeds at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 (or even more).

[0091] The IM tool mentioned above is an example of the second system. Metering system 40 is an example of the first system.

[0092] The first system can be used to provide a map of the entire wafer. The second system can be used to provide measurements at selected sites on the wafer. Figure 12 The first system (left side of the figure: "scanning module") and the second system (right side of the figure: "IM OCD measurement unit") are shown.

[0093] The first system can be a scanning module, and the second system can be a single-lens optical module.

[0094] The first and second systems can complement each other, and information from both systems can be processed together. Information from the first system can assist in site selection. Information from one system may influence how the second system operates. Information from one system can be used to verify information from the other system.

[0095] The first system allows for rapid scanning of a large portion (including the entire wafer) of the wafer during the transfer from EFEM to IM tools / from IM tools to EFEM, where the first spectral resolution may be sufficient to find one or more metrological parameters of interest, for example, allowing the capture of WIW variations.

[0096] The second system can capture vertically incident reflected and / or diffracted light to allow for flexibility and coverage in a variety of metrology and inspection applications across different areas of semiconductor manufacturing, including CMP, deposition, and patterning.

[0097] Both systems can be based on lighting using combinations of LEDs that allow the use of any combination of LEDs on one or more wavelengths, while the second system can provide coverage of a wide spectral range, for example, by using LEDs that provide aggregated coverage, such as between ultraviolet (UV) and infrared (IR): 265 nm to 960 nm, between 190-1000 nm, etc. The first system uses a limited number of wavelengths or a narrow wavelength range (a narrow wavelength range can be the range emitted by LEDs such as monochromatic LEDs, where monochromatic LEDs are not completely monochromatic).

[0098] Both the first and second systems allow for full or partial polarization control of the incident and collected light to enable operation in different states, including bright field (BF) and dark field (DF).

[0099] The first system can be located above the wafer path from the EFEM of the processing equipment to the IM tool, and captures an "image" of the wafer as it moves in the direction of the IM tool or is dispatched back to the processing equipment. In one possible implementation, the scanning module is applied in a perpendicular-incident (NI) configuration when both illumination (light from the source pointing to the sample) and collection (reflected light) are at perpendicular incidence (NI). The reflected light is collected by a lens and measured by a fast line camera (sampling rate of approximately 50 to 150 kHz to require rapid measurements). The line camera can have 10-20 K pixels with a pixel size of 5-10 μm to allow for full-wafer measurements during loading or uploading. Figure 15 The optical scheme of NI's macroscopic optics module is presented in the image.

[0100] The available volume of the first system is limited (due to the footprint of the IM), therefore the optimal system for complete imaging of the wafer is a vertical-incident beam scanning concept based on pulsed LED illumination, line or area detectors (scanning cameras), and an optical imaging system optimized for linear FOV. Acquisition of optical information can be achieved as follows: Figure 16 The entire 300 mm wafer can be scanned in a single scan, or half of the wafer (150 mm) can be scanned twice (on the way in and out). In this case, multi-wavelength sensing can be achieved using an illumination system with multiple LEDs and a camera with N lines. The timing map of this sensing can be based on the exposure time of a single LED type, which is equal to the equivalent time of wafer movement over a length corresponding to a pixel size on the wafer plane. Synchronization of wafer speed, LED switching, and the capture rate of the multi-line linear detector allows for the acquisition of multiple frames of multiple colors across the entire wafer with minimal resolution loss. Figure 5 ).

[0101] In another implementation, the first system is designed to measure diffracted or scattered light. In this implementation, the illumination and collection angles of the sample are different: the collection angle is perpendicular to the incident light, while the illumination angle is oblique.

[0102] The optical module of the first system is sized to fit the load port mounting, so that the footprint and integration of the IM tool (e.g., 6 bolts) are not affected: it has a minimum thickness (in the wafer movement direction), and the height and width are defined by existing dimensions.

[0103] IM tools.

[0104] The optical portion of an IM tool can include movable optics (wafer navigation can also be achieved via a movable wafer platform (XY-, R-θ, or a combination thereof)) – to allow for a small footprint and confinement to the size of a FOUP (the standard integration for a polisher is FE Bolt integration, where the IM tool resides at a standard port). This movable optics can allow at least one of two functions – spectral: allowing spectral measurements of the target of interest; and vision: allowing the capture of images for a variety of purposes, including pattern recognition, optimal focusing, local and global alignment, etc. The vision system, equipped with a camera (which can be monochrome, RGB, or hyperspectral) and a dedicated light source (which can be a wide wavelength range with filters, a set of LEDs, etc.), can act as a miniature optical module to capture high-resolution images at predetermined locations on the wafer (see...). Figure 14 ).

[0105] The second system may include: a. Using visual channel “micro” images collected in standard measurement sequence spectra to predict variations in the contour geometry of the region surrounding the spectral measurement point (scattering measurement point size less than 40 micrometers) (see...) Figure 14 ).

[0106] b. Modify and optimize image capture conditions and sequences to allow the collection of images for predicting die images and to examine problem areas on the wafer defined by images of the full wafer map from the scanning module and / or scattering measurement data.

[0107] All the suggested imaging solutions can also be applied to SA scattering measurement tools.

[0108] Wafer transfer.

[0109] To obtain high-quality images with minimal pixel size, it is necessary to control the movement of the wafer under the scanning system.

[0110] The uncertainties that wafer movement may involve can be divided into three categories: (1) uncertainties that the optical system can be considered without any hardware (HW) addition, (2) uncertainties that the optical system must be flexible enough to accommodate, and (3) uncertainties that are relatively easy to consider regarding wafer movement itself.

[0111] The optical system should be able to account for the few uncertainties in wafer movement, namely the uncertainties in the X and Y positions, without requiring any modifications. Furthermore, the focus can be addressed with a simple autofocus system, or it can be kept fixed by setting the specifications for the wafer's Z position.

[0112] Even if the average Z-wafer position can be fixed at the desired level, wafer curvature will affect imaging and therefore needs to be considered. For most wafers currently available, curvature is typically below + / - 250 micrometers, but can reach 500-800 micrometers, and in extreme cases of 3D NAND, even + / - 1 mm. To accommodate the varying curvatures of different wafers, optical systems have variable NA values, ranging from large NA values ​​(above 0.1-0.2 for planar wafers) to extremely small NA values ​​(0.02 and below, for measuring the limiting curvature of + / - 1 mm). In such cases, the trade-off is a slight decrease in resolution and an increase in measurement time. In any case, the imaging setup parameters will be optimized for the curved wafer and will include NA and optimized wafer speed.

[0113] Mobile systems ( Figure 15 The proposed solution should allow for a controlled and constant wafer speed defined by optimal wafer imaging setup parameters, without dynamic tilt and dynamic focus variations (both below <50-100 micrometers). All these requirements can be met by a robot, or, if the specifications of existing atmospheric point-to-point robots are insufficient, by designing a special retractable rail-mounted drawer. This drawer would acquire the wafer from the robot in front of the imaging system and scan the wafer below the imaging system at the required speed and in a controlled manner, finally transferring the wafer to the IM module for OCD measurement. In practice, this rail-mounted drawer or retractable semi-buffer should allow for wafer exchange outside the MU. At all times, the drawer remains inside the IM module; its external presence is solely for wafer pickup / return without interfering with robot movement within the EFEM.

[0114] Imaging metrology.

[0115] The goal of imaging metrology is to convert an image into a parametric map of interest across the entire image, preferably a multispectral image. Taking the measurement of the thickness of residues in a memory array as an example, an operational sequence suitable for demonstrating the proposed method is presented. This method can be used with both static and mobile optical modules.

[0116] Setting imaging metrology parameters

[0117] Step 1. Imaging conditions.

[0118] The standard OCD setup parameters are created based on spectral information collected from the features of interest (on the storage array). The interpretation includes contour information usable for image acquisition settings, encompassing all parameters of interest. This spectral information, along with the parameters of interest measured by the OCD, is used to define the optimal configuration for image acquisition (wavelength combination for image acquisition) to achieve the best performance for the target parameters of interest. This image acquisition configuration, along with the OCD setup parameters, will be used in all future measurements.

[0119] Step 2. Image processing settings.

[0120] Following preprocessing to improve image quality, image processing settings (which can also be defined as pattern recognition) are created. These settings allow for the automatic identification of regions of interest (GIs) for which we want to measure parameters, and the selection of the desired pixels (for all images captured using all wavelength combinations). As a result, an image of the GI is created: in our example, we obtain an image of the memory array. Additional processing can be applied to the pixels in the GIs, including averaging and / or noise reduction and / or other computations to stabilize metrological performance. Averaging can be performed on individual arrays, portions of the die, and the entire die, and all different averaging schemes can be used to focus on different scales of variability as required.

[0121] Step 3. Machine learning (ML) settings for image parameters.

[0122] The X and Y coordinates of these arrays are then matched with the coordinates of the OCD measurements to allow a direct correlation between the image parameters and the OCD reference measurements, and ML setting parameters are created. ML setting parameters allow the image parameters to be transformed into measurement parameters of interest. The ML setting parameters are then trained, tested, and validated using standard methods.

[0123] Step 4. Optional – Fine-tuning of extreme edges

[0124] Special handling may be required for extreme edges – additional OCD measurements and / or additional OCD setting parameters (fine-tuning) may be needed to obtain the best extreme edge description.

[0125] Imaging metrology.

[0126] For all wafers, standard OCD settings are used to measure parameters of interest at predefined locations (12 to 100 points per wafer). Images are collected and processed under required conditions. Image parameters from OCD results at the same locations (for all parameters of interest) are used together to allow for accurate image metrology on each wafer.

[0127] Interpreting an image as a parametric map can be done in a variety of ways, including on-the-fly ML methods based on profile parameters measured at one of the image locations on the current wafer and / or on a specially prepared DOE wafer (standard scattering measurement) and / or prior knowledge about the wafer and its fabrication.

[0128] An imaging device may be provided, which may include: an imaging device configured to image a wafer at a first spectral resolution, a first throughput, and during the wafer's movement between a metrology device and another device, wherein the first spectral resolution is coarser than a second spectral resolution of the metrology device, and wherein the first throughput exceeds the second throughput of the metrology device; and a mechanical interface for mechanically coupling the imaging device to the metrology device.

[0129] Imaging equipment can be configured to measure features of a wafer.

[0130] The imaging device may include an illumination module that can be configured to scan the wafer with at least one illumination line during wafer movement.

[0131] The imaging device includes an illumination module that can be configured to scan the wafer with different illumination lines during wafer movement. These illumination lines have different illumination frequencies and are formed on the wafer with different and non-overlapping illumination cycles.

[0132] Each illumination line can be perpendicular to the direction of wafer movement.

[0133] The illumination can be a vertical illumination of the wafer.

[0134] The imaging device may include a collection module having an optical axis that is perpendicular to the wafer.

[0135] The illumination module may include an optical unit configured to convert an incoming circular cross-section of radiating light beam into linear radiation.

[0136] Figure 16 Method 300 is shown.

[0137] Method 300 may include step 310: acquiring optical information about a wafer via a first system at a first spectral resolution, a first throughput, and during the wafer's movement between a metrology device and another device, wherein the first spectral resolution is coarser than a second spectral resolution of a second system, and wherein the first throughput exceeds the second throughput of the second system; wherein the first system is mechanically coupled to the second system via a mechanical interface. The first system may be an imaging system or a non-imaging system. The second system may be a metrology device, an IM tool, etc.

[0138] Step 310 can be followed by step 320: measuring the characteristics of the wafer using the first system. These characteristics may be metrological parameters.

[0139] Step 310 can be performed during step 305, whereby step 305 involves scanning the wafer with at least one illumination line during wafer movement using the illumination module of the first system. Multiple lines are possible, but the number of lines is much smaller than the number of pixels per line. Examples include 5-10 lines, 10-20 lines, 20-40 lines, 15-50 lines, etc.

[0140] Step 305 may include scanning the wafer with different illumination lines by the illumination module of the first system during wafer movement, the illumination frequencies of these illumination lines being different from each other, wherein the different illumination lines are formed on the wafer with different and non-overlapping illumination cycles.

[0141] Each illumination line can be perpendicular to the direction of wafer movement.

[0142] Irradiation can be vertical irradiation of the wafer.

[0143] The first system may include a collection module having an optical axis that can be perpendicular to the wafer.

[0144] Step 310 may include converting the incoming circular cross-section radiation beam into linear radiation through the optical unit of the first system.

[0145] Figure 17 Method 400 is shown.

[0146] Method 400 may include step 410: acquiring wafer-related optical information via processing circuitry, the image being generated by a first system and having a first spectral resolution, the acquisition of the optical information being performed at a first throughput and while the wafer is moving between a second system and another device.

[0147] Method 400 may further include step 420: acquiring second system results associated with one or more regions of the wafer via processing circuitry, wherein the metrological results are generated by a second system that can be configured to perform feature measurements within the regions of the wafer at a second spectral resolution that can be finer than the first spectral resolution and at a second throughput that can be lower than the first throughput.

[0148] Steps 410 and 420 may be followed by step 430: estimating metrological results related to one or more additional regions of the wafer based on (a) the mapping between the first system results and the second system results, (b) the first system results, and (c) the second system results; wherein the one or more additional regions are not included in the one or more regions in step 420.

[0149] This application provides a more significant technological improvement than the prior art, particularly in the field of computer science.

[0150] Any reference to the terms “comprising” or “having” should also be interpreted as “consisting of” or “substantially consisting of”. For example, a method that includes certain steps may include additional steps, may be limited to certain steps, or may include additional steps that do not substantially affect the essential and novel features of the method.

[0151] The present invention can also be implemented in a computer program for running on a computer system, including at least a code portion for executing steps of the method according to the invention when run on a programmable device such as a computer system, or for causing the programmable device to perform the functions of a device or system according to the invention. The computer program can cause a storage system to allocate disk drives to a group of disk drives.

[0152] A computer program is a list of instructions, such as a specific application and / or operating system. A computer program may include, for example, one or more of the following: subroutines, functions, programs, object methods, object implementations, executable applications, applets, service applets (servlets), source code, object code, shared libraries / dynamically loaded libraries, and / or other sequences of instructions designed to be executed on a computer system.

[0153] Computer programs can be stored internally on computer program products, such as non-transitory computer-readable media. All or part of a computer program can be provided on computer-readable media permanently, removably, or remotely coupled to an information processing system. Computer-readable media can include, for example, but not limited to, any of the following: magnetic storage media, including magnetic disk and magnetic tape storage media; optical storage media, such as optical disc media (e.g., CD-ROM, CD-R, etc.) and digital video disk storage media; non-volatile memory storage media, including semiconductor-based memory cells such as FLASH memory, EEPROM, EPROM, ROM; ferromagnetic digital memory; MRAM; volatile storage media, including registers, buffers or caches, main memory, RAM, etc. A computer process typically includes a program or part of a program that is executing (running), current program values ​​and state information, and resources used by the operating system to manage process execution. The operating system (OS) is software that manages shared computer resources and provides programmers with an interface to access these resources. The operating system processes system data and user input and responds by allocating and managing tasks and internal system resources as services to users and programs on the system. For example, a computer system may include at least one processing unit, associated memory, and some input / output (I / O) devices. When executing a computer program, the computer system processes information according to the computer program and generates result output information through the I / O devices.

[0154] In the foregoing specification, the present invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims.

[0155] Furthermore, the terms "front," "rear," "upper," "lower," etc., used in the specification and claims, if applicable, are for descriptive purposes and are not necessarily used to describe permanent relative positions. It is understood that such terms are interchangeable where appropriate; for example, embodiments of the invention described herein can operate in directions other than those described herein or otherwise.

[0156] Those skilled in the art will recognize that the boundaries between logic blocks are merely illustrative, and alternative implementations may combine logic blocks or circuit elements, or impose alternative functional decompositions on various logic blocks or circuit elements. Therefore, it should be understood that the architecture described herein is merely exemplary, and in fact, many other architectures can achieve the same functionality.

[0157] The arrangement of any components that achieve the same function is essentially “related” to achieve the desired functionality. Therefore, any two components combined here to achieve a specific function can be considered “related” to each other to achieve the desired functionality, regardless of the architecture or intermediate components. Similarly, any two such related components can also be considered “operably connected” or “operably linked” to each other to achieve the desired functionality.

[0158] Furthermore, those skilled in the art will recognize that the boundaries between the above operations are merely illustrative. Multiple operations can be combined into a single operation, a single operation can be distributed among additional operations, and operations can be performed at least partially overlapping in time. Moreover, alternative implementations may include multiple instances of a particular operation, and the order of operations may be varied in various other implementations.

[0159] For example, in one embodiment, the described implementation can be a circuit located on a single integrated circuit or within the same device. Alternatively, the implementation can be implemented as any number of separate integrated circuits or separate devices interconnected in a suitable manner.

[0160] For example, this embodiment or a portion thereof may be implemented as a physical circuit or a logic representation that can be converted into a physical circuit, such as in any suitable type of hardware description language.

[0161] Furthermore, the present invention is not limited to physical devices or units implemented in non-programmable hardware, but can also be applied to programmable devices or units that can perform desired device functions by operating in accordance with appropriate program code, such as host computers, microcomputers, servers, workstations, personal computers, notebooks, personal digital assistants, video games, automobiles and other embedded systems, mobile phones and various other wireless devices, which are generally referred to as 'computer systems' in this application.

[0162] However, other modifications, changes, and alternatives are possible. Therefore, this specification and accompanying drawings should be viewed in an illustrative rather than restrictive sense.

[0163] In the claims, any reference signs enclosed in parentheses should not be construed as limiting the claims. The word "includes" does not exclude the presence of other elements or steps, followed by those listed in the claims. Furthermore, the terms "a" or "an" as used herein are defined as one or more. Additionally, the use of introductory phrases such as "at least one" and "one or more" in the claims should not be construed as implying that the introduction of another claim element by the indefinite clause "a" or "an" limits any particular claim containing such an introduced claim element to an invention containing only one such element, even if the same claim includes the introductory phrase "one or more" or "at least one" and the indefinite clause such as "a" or "an". The same applies to the use of definite articles. Unless otherwise stated, terms such as "first" and "second" are used to arbitrarily distinguish the elements described by these terms. Therefore, these terms are not necessarily intended to indicate the time or other priority of these elements. The mere fact that certain measures are mentioned in mutually different claims does not indicate that a combination of these measures cannot be used to exert an advantage.

[0164] While certain features of the invention have been described and illustrated herein, many modifications, substitutions, variations, and equivalents will appear to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and variations that fall within the true spirit and scope of the invention.

Claims

1. An optical metrology method for a sample, the method comprising: During the variable-speed movement of the sample, the sample area is irradiated by multiple sets of pulses of different wavelengths; Light reflected from the sample as a result of irradiation is collected to provide multiple sets of frames, each set of frames comprising multiple partially overlapping frames associated with the different wavelengths; as well as The frames are processed to provide optical metrological results indicating one or more evaluation parameters of elements in a region of the sample; wherein the processing is based on a mapping between the multiple sets of frames and reference measurements obtained through other optical metrological processes that exhibit a higher spectral resolution than those obtained through illumination and collection.

2. The method of claim 1, wherein, Other measurement processes are integrated measurement processes performed through integrated measurement tools.

3. The method of claim 1, wherein, The different wavelengths mentioned are discrete wavelengths.

4. The method according to claim 1, wherein, The sample is a bare wafer, and the method includes sensing the location of at least a portion of the edge of the bare wafer during irradiation and collection.

5. The method according to claim 4, comprising: The location of the region is determined based on the position of at least a portion of the edge.

6. The method according to claim 5, wherein, The process includes generating a map of the bare wafer at the specific wavelength based on frames associated with a specific wavelength among the different wavelengths and the location of the region associated with the frames.

7. The method according to claim 1, wherein, Frames that are associated with the same wavelength but belong to different frame groups partially overlap.

8. The method according to claim 1, wherein, The mapping is provided through a machine learning process.

9. The method according to claim 8, wherein, The machine learning process is trained through a training process that includes supplying the machine learning process with: (a) test measurements of one or more test samples obtained through the other optical metrology processes and information, and (b) additional test measurements of the one or more test samples obtained through the optical metrology methods.

10. The method according to claim 1, wherein, Irradiation and collection are performed as the sample is moved from the chamber to the housing by a robot.

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