Calibration for in-plane twist tool-to-tool matching

Abstract

A shape map can be extracted for a workpiece, such as a semiconductor wafer. A calibration map for the workpiece can be extracted from the shape map to produce a calibrated shape map. In-plane twist matching can be performed using the calibrated shape map. The in-plane twist matching can be performed between two metrology tools.

Description

Technical Field

[0001] This disclosure relates to workpiece measurement. Background Technology

[0002] The evolution of the semiconductor manufacturing industry has placed higher demands on yield management, particularly on metrology and inspection systems. Critical dimensions continue to shrink, and the industry needs to reduce the time spent achieving high-yield, high-value production. Minimizing the total time from detecting a yield problem to resolving it will maximize the return on investment for semiconductor manufacturers.

[0003] Fabricating semiconductor devices, such as logic and memory devices, typically involves using numerous fabrication processes to work a workpiece (e.g., a semiconductor wafer) to form the various features and multiple layers of the semiconductor device. For example, photolithography is a semiconductor fabrication process that involves transferring a pattern from a photomask to a photoresist disposed on a semiconductor wafer. Additional examples of semiconductor fabrication processes include (but are not limited to) chemical mechanical polishing (CMP), etching, deposition, and ion implantation. The arrangement of multiple semiconductor devices fabricated on a single semiconductor wafer can be separated into several individual semiconductor devices.

[0004] Metrology processes are used at various steps during semiconductor manufacturing to monitor and control the process. Metrology differs from inspection processes in that, unlike inspection processes which detect defects on a workpiece, metrology is used to measure one or more characteristics of a workpiece that cannot be determined using existing inspection tools. Metrology can be used to measure one or more characteristics of a workpiece so that the performance of the process can be determined from said one or more characteristics. For example, metrology can measure the dimensions (e.g., linewidth, thickness, etc.) of features formed on a workpiece during the process. Furthermore, if one or more characteristics of a workpiece are unacceptable (e.g., outside a predetermined range), the measurements of those characteristics can be used to modify one or more parameters of the process so that additional workpieces manufactured by the process have acceptable characteristics.

[0005] Interferometers are used for metrology in the semiconductor industry. The workpiece remains stationary during interferometric measurements. In most metrology tools, a tray with three grippers is used to hold the workpiece. However, to keep the workpiece stationary, a specific amount of force needs to be applied by the grippers at the workpiece contact points, which inevitably causes some deformation or distortion to the workpiece shape. This distortion varies between tools or between trays. Therefore, the workpiece shape measured from different tools or trays will be significantly affected by this gripper-induced distortion, and mismatch can prevent the tool from meeting in-line monitoring requirements. Among many shape-related metrics, in-plane distortion (IPD) is identified as one of the most effective in-line monitoring indicators. Therefore, monitoring IPD tool-to-tool matching is a critical metrology criterion, even though such monitoring is largely affected by gripper-induced distortion.

[0006] Typically, specific requirements are established for workpiece flatness and thickness uniformity. However, clamping a workpiece with variations in shape (defined as the intermediate surface of the workpiece obtained from the front and rear surfaces of the wafer in its free state) and thickness causes elastic deformation, which can lead to interphase deviation (IPD). IPD can introduce errors in downstream applications, such as photolithographic patterning or, for example, overlay errors in such applications. Therefore, providing the ability to predict / estimate IPD due to wafer shape during clamping processes and to control workpiece shape specifications can improve semiconductor manufacturing processes.

[0007] A challenge in developing metrology systems that meet the requirements of semiconductor manufacturers is achieving tool-to-tool matching and maintaining consistent tool measurements across time, maintenance cycles, and a wide range of measurement applications. Process and yield controls in both research and development and manufacturing environments necessitate tool-to-tool consistency of measurement results to a level that approximates measurement repeatability. Therefore, methods and systems are needed to achieve improved tool-to-tool matching and consistent measurement performance across a broad range of measurement applications. Summary of the Invention

[0008] A method is provided in a first embodiment. The method includes extracting a shape map of a workpiece using a processor. A calibration map of the workpiece is subtracted from the shape map using the processor to generate a calibrated shape map. The processor is then used to determine in-plane torsion matching using the calibrated shape map.

[0009] The method may further include acquiring images of the workpiece at multiple angles. The multiple angles may include at least three angles. The processor may be used to determine a first averaged shape map obtained from the multiple angles and a second shape map obtained from an angle of 0°. The processor may be used to subtract the second shape map from the first averaged shape map to generate the calibration map. The multiple angles may include twelve angles.

[0010] The workpiece may be a semiconductor wafer.

[0011] The method may further include associating the calibrated shape map with a tray configured to hold the workpiece.

[0012] The in-plane torsion matching can be performed between two measuring tools. In one example, each measuring tool is an interferometer tool. The in-plane torsion matching can also be performed between two trays, each configured to hold the workpiece.

[0013] The second shape map can be obtained by averaging multiple 0° angle shape maps.

[0014] A non-transitory computer-readable medium storing a program can be configured to instruct a processor to perform the method of the first embodiment.

[0015] A second embodiment provides a system. The system includes an interferometer tool configured to obtain one or more measurements of a workpiece. The one or more measurements include one or more in-plane torsion measurements of the workpiece. A processor communicates electronically with the interferometer tool. The processor is configured to: extract a shape map of the workpiece; subtract a calibration map of the workpiece from the shape map to generate a calibrated shape map; and use the calibrated shape map to determine in-plane torsion matching.

[0016] The processor may be further configured to: receive images of the workpiece obtained from multiple angles around the workpiece; determine a first averaged shape map obtained from the multiple angles; determine a second shape map obtained from an angle of 0°; and subtract the second shape map from the first averaged shape map to generate the calibration map. The multiple angles include at least three angles. In one example, the multiple angles include twelve angles.

[0017] The workpiece may be a semiconductor wafer.

[0018] The processor may be further configured to associate the calibrated shape map with a tray configured to hold the workpiece.

[0019] The second shape map can be obtained by averaging multiple 0° angle shape maps.

[0020] The in-plane torsion matching can be performed between the interferometer tool and another interferometer tool. The in-plane torsion matching can also be performed between two trays configured to hold the workpiece. One of the trays is part of the interferometer tool. Attached Figure Description

[0021] For a more complete understanding of the nature and purpose of this disclosure, reference should be made to the following detailed description in conjunction with the accompanying drawings, in which:

[0022] Figure 1 The demonstration shows how a gripper's shape mismatch between two tools causes distortion.

[0023] Figure 2 This is a flowchart illustrating an embodiment of the method according to the present disclosure;

[0024] Figure 3 Examples illustrating the process of generating a calibration map according to this disclosure; and

[0025] Figure 4 This is an embodiment of the system according to the present disclosure. Detailed Implementation

[0026] Although the claimed subject matter will be described with reference to specific embodiments, other embodiments, including those that do not provide all of the benefits and features set forth herein, are also within the scope of this disclosure. Various structural, logical, procedural, and electronic changes may be made without departing from the scope of this disclosure. Therefore, the scope of this disclosure is defined only by reference to the appended claims.

[0027] The embodiments disclosed herein improve IPD tool-to-tool matching by obtaining the workpiece shape at multiple different angles. The averaged shape can be considered as the actual shape of the workpiece because the gripper-induced distortion has been minimized multiple times at each rotation angle. The gripper-induced distortion from the measuring tool or pallet, which is the calibration profile of the measuring tool or pallet, can then be calculated by the offset of the actual shape relative to the shape obtained at the normal angle. When the calibration profile is subtracted from subsequent measurements, the calibrated shape can be considered as having "no" gripper-induced distortion, which minimizes mismatch when evaluating IPD tool-to-tool matching.

[0028] IPD (In-line Diagram Proportion) is a shape-induced overlap metric and is considered one of the largest and most effective in-line monitoring indicators. Therefore, good IPD tool-to-tool matching is desirable. The embodiments disclosed herein improve IPD tool-to-tool matching via an offset from a calibration map. A calibration map can be obtained by rotating the workpiece, for example, by 12 degrees. The 0° shape map is subtracted from the average of the shape maps generated from all angles. The calibration map can then be associated with each pallet.

[0029] It was observed that the mismatch problem area typically occurred in the tray holder area, which serves as the contact point between the tray and the wafer, such as... Figure 1As shown in the diagram, tray holder-induced distortion is a major cause of IPD tool-to-tool mismatch, and this distortion is often more dependent on the metrology tool or tray than on the workpiece. Therefore, angular calibration is used for each tray or metrology tool to improve IPD tool-to-tool matching. After performing calibration steps in which the shape of the calibrated wafer is obtained at various angles, a calibration profile is calculated through averaging and subtraction steps, which is then used to offset the measurement data before performing IPD matching.

[0030] Figure 2 This is a flowchart of method 200. One or more steps of method 200 can be executed using a processor.

[0031] At point 201, a shape map of the workpiece is extracted, which may be a semiconductor wafer. In one example, the shape map is extracted by calculating the intermediate surface between the front and rear planes of the workpiece, which can be measured using an interferometer. In another example, the shape map can be extracted from the workpiece's design documents or specifications.

[0032] For example, images of a workpiece can be acquired at multiple angles around it. The number of angles used can be at least three. Additional angles are possible. For example, twelve angles can be used. In one example, angles are acquired in 30° increments. Images can be acquired around the workpiece at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°. In another example, images can be acquired around the workpiece at 0°, 120°, and 240°. The workpiece can be generally circular, so the image is captured around the circumference when measured from the start or end point.

[0033] The more angles used, the more accurate the results. However, this increases processing time. Fewer angles result in less accurate results, despite reduced processing time. Fewer than three angles may not provide sufficient accuracy. More than twelve angles are possible.

[0034] The position of the 0° angle can vary depending on the workpiece. For example, the 0° angle can be a notch on the workpiece or the edge of the workpiece opposite the notch. For most workpieces, the position of 0° does not affect the results.

[0035] Based on multiple perspectives, a first averaged shape map can be determined. This can be referred to as the shape. 所有角度 (Shape all angles Each of the shape maps taken from different angles can be averaged. A second shape map, which can be called the shape map, can be determined by taking an angle from 0°. 0° (Shape 0°For example, a user can collect multiple images at a 0° acquisition angle and average these images to produce a second shape image. Alternatively, a user can collect a single image at a 0° acquisition angle as the second shape image, without averaging. The 0° acquisition angle used for the second shape image can be a portion of other images used herein or can be a single image.

[0036] For example, using image subtraction, a second shape map can be subtracted from a first averaged shape map. This produces a calibration map. The calibration map can be saved to memory after its generation and can be used for later in-plane warp matching. Calibration maps can be generated periodically for a specific tray or a specific tool. For example, this step can be performed every few months or when a new tray is installed on the tool.

[0037] Figure 3 An example of the process for generating a calibration map is shown. As illustrated in the array, twelve images of the workpiece are acquired. The 0° image is subtracted to generate the calibration map. Figure 3 The ideal (golden) shape of the wafer is an averaged shape map of all acquired angles. A calibration map can be obtained by subtracting the ideal wafer shape from the 0° shape map.

[0038] Return to Figure 2 At position 202, for example using image subtraction, the workpiece calibration map is subtracted from the shape map to produce a calibrated shape map. The calibration map contains pallet-specific shape distortion or tool-specific shape distortion. The calibrated shape map can be associated with a pallet configured to hold the workpiece.

[0039] At 203, in-plane torsion matching is determined using a calibrated shape map. In one embodiment, in-plane torsion matching can be performed between two metrological tools. For example, two interferometer tools can perform in-plane torsion matching. In another embodiment, in-plane torsion matching can be performed between two pallets, each configured to hold a workpiece or different workpieces. In-plane torsion calculation is standard practice as specified in the SEMI standard. In-plane torsion matching is used to derive the difference in in-plane torsion determined from the same workpiece when measured in different processes and / or tools.

[0040] In one embodiment, in-plane torsion matching is performed by acquiring a wafer shape map. The acquired shape map can be calibrated by subtracting a calibrated shape map for the tool or tray. The resulting shape map after calibration can then be used for in-plane torsion matching.

[0041] Interferometer tools may include any interferometer tool well known in the art. For example, an interferometer tool may be configured to measure any number of spatial characteristics of a workpiece, including, but not limited to, flatness, shape variations, thickness variations, and / or any other spatial parameter variations of the workpiece. The spatial characteristics of the workpiece may be related to the wafer geometry of the workpiece and may additionally be represented by out-of-plane distortion (OPD). Descriptions of using wafer geometry measurements for stacking and semiconductor process control are described in U.S. Patent No. 9,354,526, the entire contents of which are incorporated herein by reference. Additionally, descriptions of using wafer geometry measurements for stacking and semiconductor process control are described in U.S. Patent Publication No. 2016 / 0372353, the entire contents of which are incorporated herein by reference.

[0042] In another example, the interferometer tool may include, but is not limited to, a dual-wavelength dual-interferometer. For example, a dual-wavelength dual-interferometer may include, but is not limited to, a dual-wavelength dual-Fizeau interferometer (DWDFI). In another example, the interferometer tool may be adapted to perform patterned wafer geometry (PWG) measurements on a workpiece, thereby extending the dynamic range of the sample slope (e.g., wafer slope) measured by the interferometer tool by stitching together the measurement results from different regions of the workpiece.

[0043] A description of a dual-wavelength dual-interferometer is provided in U.S. Patent No. 6,847,458, the entire contents of which are incorporated herein by reference. Additionally, a description of a dual-wavelength dual-interferometer is provided in U.S. Patent No. 8,068,234, the entire contents of which are incorporated herein by reference.

[0044] Figure 4 This is an embodiment of system 100. In system 100, the interferometer tool 101 includes a workpiece 102 (e.g., a semiconductor wafer) on a tray 103 or other stage or platform. The processor 104 communicates electronically with the interferometer tool 101. The interferometer tool 101 may include a measurement system as described elsewhere herein.

[0045] While disclosed using in-plane twist matching, other shape-related metrics can benefit from the embodiments disclosed herein. For example, bending or warping of a workpiece can benefit from the embodiments disclosed herein.

[0046] As used herein, the term "workpiece" generally refers to a wafer (e.g., a semiconductor wafer) formed from semiconductor or non-semiconductor materials. Examples of such semiconductor or non-semiconductor materials include, but are not limited to, single-crystal silicon, gallium nitride, gallium arsenide, indium phosphide, sapphire, and glass. Such wafers are typically found and / or processed in semiconductor fabrication facilities.

[0047] A workpiece may contain one or more layers formed thereon. For example, such layers may include, but are not limited to, photoresist, dielectric material, conductive material, and semiconductive material. Many different types of such layers are well known in the art, and the term workpiece as used herein is intended to encompass workpieces containing all types of such layers.

[0048] One or more layers formed on a workpiece may be patterned or unpatterned. For example, a workpiece may comprise multiple blanks, each having repeatable patterned features or periodic structures. The formation and processing of such material layers can ultimately produce a finished device. Many different types of devices can be formed on a workpiece, and the term workpiece, as used herein, is intended to encompass any type of device well known in the art.

[0049] Other types of workpieces can also be used. For example, the workpieces can be used to manufacture LEDs, solar cells, disks, flat panels, or polished plates. The techniques and systems disclosed herein can also be used to classify defects on other objects.

[0050] Although this disclosure has been described with respect to one or more specific embodiments, it should be understood that other embodiments of this disclosure may be made without departing from the scope of this disclosure. Therefore, this disclosure is to be considered limited only by the appended claims and their reasonable interpretation.

Claims

1. A method comprising: Use the processor to extract the shape map of the workpiece; The processor is used to subtract the calibration map of the workpiece from the shape map to generate a calibrated shape map; as well as The processor is used to determine in-plane twist matching using the calibrated shape map.

2. The method according to claim 1, further comprising: Images of the workpiece are acquired from multiple angles, wherein the multiple angles include at least three angles; The processor is used to determine a first averaged shape map obtained from the plurality of angles; The processor is used to determine a second shape map obtained from the angle acquired at 0°. as well as The processor is used to subtract the second shape map from the first averaged shape map to generate the calibration map.

3. The method according to claim 2, wherein the plurality of angles comprises twelve angles.

4. The method according to claim 1, wherein the workpiece is a semiconductor wafer.

5. The method of claim 1, further comprising associating the calibrated shape map with a tray configured to hold the workpiece.

6. The method of claim 1, wherein the in-plane torsion matching is performed between two metrological instruments.

7. The method according to claim 6, wherein each of the measuring tools is an interferometer tool.

8. The method of claim 1, wherein the in-plane torsion matching is performed between two pallets, each of which is configured to hold the workpiece.

9. The method of claim 1, wherein the second shape map is obtained by averaging a plurality of 0° angle shape maps.

10. A non-transitory computer-readable medium storing a program configured to instruct a processor to perform the method according to claim 1.

11. A system comprising: An interferometer tool configured to obtain one or more measurements of a workpiece, wherein the one or more measurements include one or more in-plane torsion measurements of the workpiece. as well as A processor that communicates electronically with the interferometer tool, wherein the processor is configured to: Extract the shape map of the workpiece; Subtract the calibration map of the workpiece from the shape map to generate a calibrated shape map; and The calibrated shape map is used to determine in-plane twist matching.

12. The system of claim 11, wherein the processor is further configured to: Receive images of the workpiece obtained from multiple angles around the workpiece, wherein the multiple angles include at least three angles; Determine the first averaged shape map obtained from the multiple angles; Determine the second shape map obtained from the angle of 0°; and The calibration map is generated by subtracting the second shape map from the first averaged shape map.

13. The system of claim 12, wherein the plurality of angles comprises twelve angles.

14. The system of claim 11, wherein the workpiece is a semiconductor wafer.

15. The system of claim 11, wherein the processor is further configured to associate the calibrated shape map with a tray configured to hold the workpiece.

16. The system of claim 11, wherein the in-plane twist matching is performed between the interferometer tool and another interferometer tool.

17. The system of claim 11, wherein the in-plane twist matching is performed between two trays configured to hold the workpiece, wherein one of the trays is part of the interferometer tool.

18. The system of claim 11, wherein the second shape map is obtained by averaging a plurality of 0° angle shape maps.

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