Stepper and overlay adjustment device for a stepper
Patent Information
- Application Number
- CN202522578559.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-04
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2035-12-04
AI Technical Summary
Existing stepper lithography machines have difficulty effectively controlling the overlay residuals caused by local deformation within a single exposure unit, resulting in poor pattern alignment consistency and affecting product performance and yield.
An overlay adjustment device is adopted, including an overlay means measuring device and a beam means: the overlay and beam adjuster are realized by a multi-axis driver and controller, and the refraction path of the exposure light is adjusted by an adjustable lens and a multi-axis driver to achieve compensation for the overlay residual within a single exposure unit.
It achieves precise compensation for overlay residuals within a single exposure unit, improves pattern alignment consistency, adapts to the needs of multi-variety production, reduces costs, and improves process yield.
Smart Images
Figure CN224934297U_ABST
Abstract
Description
Technical Field
[0001] This application relates to photolithography technology, and in particular to a stepper lithography machine and an overlay adjustment device for the stepper lithography machine. Background Technology
[0002] In semiconductor manufacturing, photolithography is a core step in pattern transfer, and the alignment accuracy (overlay) between different layers directly determines the functional integrity and reliability of the chip. As chip process nodes continue to shrink, while continuously increasing device integration, it also poses a significant challenge to the overlay accuracy of photolithography machines.
[0003] While stepper lithography machines, widely used in the industry, can correct overall overlay deviations between different exposure units through field-by-field exposure, they lack effective means to control overlay residuals caused by localized deformation within individual exposure units. This technological limitation results in some products having overlay residuals exceeding specifications within exposure units (Shots), severely affecting pattern alignment consistency and ultimately causing products to fail to meet performance standards and be unavailable for delivery, becoming a key bottleneck restricting the improvement of yield in advanced processes. Utility Model Content
[0004] Therefore, it is necessary to provide a stepper lithography machine and an overlay adjustment device for the stepper lithography machine to address the problems mentioned above, which can at least compensate for the overlay residual within a single exposure unit (Shot).
[0005] To address the aforementioned technical and other issues, one aspect of this application provides an overlay adjustment device, comprising: an overlay residual measuring instrument for acquiring the overlay residual of the overlay sample to be measured;
[0006] A beam adjuster, located directly below the overlay sample to be tested, includes: an adjustable lens and a multi-axis driver; the multi-axis driver is used to drive the adjustable lens to move along multiple points to generate a preset angle of curvature, so as to change the position of the overlay sample to be tested projected on the exposure plane.
[0007] The controller, connected to the overlay residual measuring device and the beam adjuster, is used to generate an adjustment amount and drive the multi-axis driver to perform the corresponding action when the overlay residual is received.
[0008] In the above embodiments, the overlay adjustment device is set in the exposure optical path of the stepper lithography machine. The adjustable lens is adjusted by a multi-axis driver to produce bending, so that the exposure light is refracted when it passes through the adjustable lens, thereby changing the position of the overlay sample to be tested projected on the exposure plane, and realizing compensation for the overlay residual in a single exposure unit.
[0009] In some embodiments, the multi-axis driver includes a support frame and at least eight drive units uniformly and symmetrically arranged on the support frame; wherein each drive unit has an independent stroke.
[0010] In the above embodiments, at least eight-axis drive units provide high degrees of freedom, enabling more precise compensation for overlay errors. The symmetrical layout ensures uniform pressure distribution, preventing lens deformation or damage.
[0011] In some embodiments, the drive unit includes a body, with a limiting member on the top sidewall of the body and the bottom end fixedly mounted on a support frame; the limiting member is used to press against the edge of the adjustable lens.
[0012] The limiting component is also equipped with an adjusting component, and rotating the adjusting component can adjust the amount of clamping force applied by the limiting component to the edge of the adjustable lens.
[0013] In some embodiments, the body includes an electric pole;
[0014] Driven by the controller, the electric rod extends and retracts in a direction perpendicular to the exposure plane, allowing the adjustable lens to bend independently at multiple points.
[0015] In the above embodiments, the adjustable lens can be bent in the vertical direction by extending and retracting the electric rod, allowing the adjustable lens to bend independently at multiple points to form the desired preset angle.
[0016] In some embodiments, an electric slide rail is provided on the side wall of the body facing the adjustable lens, and a limiting member is installed on the electric slide rail;
[0017] The electric slide rail is electrically connected to the controller; it is used to drive the limiting component to slide up and down along the electric slide rail so that the adjustable lens can bend independently at multiple points.
[0018] In the above embodiments, the limiting member controls the curvature of the adjustable lens edge by sliding up and down on an electric slide rail. Since each drive unit has an independent stroke, the adjustable lens is allowed to bend independently at multiple points to form the desired preset angle.
[0019] In some embodiments, the overlay residual measuring instrument includes:
[0020] The sensor is used to scan the wafer pattern and the corresponding image of the overlay sample to be tested on the exposure plane to obtain a first scan image and a second scan image.
[0021] A processor for generating overlay residuals upon receiving a first scanned image and a second scanned image.
[0022] In some embodiments, the bending amount of the adjustable lens at each point is no greater than 3‰.
[0023] In some embodiments, the area of the adjustable lens is not less than the area of the overlay sample to be tested.
[0024] In some embodiments, the ratio of the area of the overlay sample to the wafer pattern size is 4:1.
[0025] In the overlay adjustment device in the above embodiments, the bending amount of the edge of the adjustable lens is limited to prevent the adjustable lens from breaking due to excessive bending. Its area is not less than that of the overlay sample to be tested, which can ensure that the entire exposure unit is covered.
[0026] Secondly, this application provides a stepper lithography machine, including the overlay adjustment device as described in any of the above embodiments.
[0027] The stepper lithography machine and the overlay adjustment device for the stepper lithography machine provided in this application have the following unexpected technical effects:
[0028] By integrating a high-precision overlay residual measuring device and a beam adjuster for optical adjustment, effective compensation for overlay residuals within a single exposure unit (shot) is achieved. Specifically, the overlay residual measuring device scans the wafer pattern and the image of the sample under test (SUT) to generate the overlay residual; the controller calculates the adjustment amount based on the overlay residual and drives a multi-axis driver to bend the edge of the adjustable lens, thereby changing the optical path of the exposure beam and the projection position of the SUT sample, thus compensating for the overlay residual. This overcomes the limitations of local alignment deviations within a single exposure unit in related technologies, meets the requirements of miniaturization processes, and provides a reliable solution for semiconductor manufacturing. Attached Figure Description
[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.
[0030] Figure 1 This is a schematic diagram showing the comparison of the states before and after adjustment between exposure units and within a single exposure unit in the conventional overlay residual calibration method for stepper lithography machines;
[0031] Figure 2 This is a schematic diagram of the overlay adjustment device provided in one embodiment of this application;
[0032] Figure 3 This is a schematic diagram of the optical path of an adjustable lens provided in one embodiment of this application;
[0033] Figure 4This is a schematic diagram showing the specific mounting relationship between the multi-axis driver and the adjustable lens provided in one embodiment of this application;
[0034] Figure 5 for Figure 4 A schematic diagram of the drive unit in the diagram;
[0035] Figure 6 This is a schematic diagram of the drive unit in another embodiment of this application;
[0036] Figure 7 This is a schematic diagram of the optical path of a stepper lithography machine provided in one embodiment of this application;
[0037] Figure 8 One of the schematic diagrams illustrating the vector change of the overlay residual when using the overlay adjustment device provided in this application;
[0038] Figure 9 The second schematic diagram shows the vector change of the overlay residual when using the overlay adjustment device provided in this application.
[0039] Explanation of reference numerals in the attached figures:
[0040] 1. Overlay residual measuring instrument; 2. Beam adjuster; 21. Adjustable lens; 22. Multi-axis driver; 221. Body; 222. Limiting component; 223. Electric slide rail; 3. Controller; 4. Overlay sample to be measured; 5. Focusing lens group. Detailed Implementation
[0041] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.
[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0043] When using the terms “including,” “having,” and “comprising” as described herein, another component may be added unless explicitly qualifying terms such as “only,” “consisting of,” etc. are used. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.
[0044] It should be understood that although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this application, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.
[0045] In this application, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a direct connection or an indirect connection through an intermediate medium, or they can refer to the internal connection of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0046] Figure 1 This diagram illustrates the comparison of the states before and after adjustment between exposure units and within a single exposure unit in the conventional overlay residual calibration method for stepper lithography machines. Figure 1 Image (a) shows the state before and after adjustment between the exposure units (Shots). Figure 1 (b) shows the state before and after adjustment within a single exposure unit (Shot). See, conventional calibration methods can only adjust the overlay residual between exposure units (Shots), and cannot calibrate the overlay residual within an exposure unit (Shot).
[0047] The front glass of a lithography machine can compensate for the overlay residuals within the exposure unit (Shot) to some extent, but it also has significant drawbacks: On the one hand, adjustments require customized reprocessing of the front glass to match its optical properties with a specific machine, with a single processing cost as high as RMB 1 million, making it extremely uneconomical; on the other hand, the fixed structure of the front glass means that it cannot be flexibly adapted to the production needs of different products by changing recipes after installation, making it difficult to cope with the multi-variety, high-iteration production scenarios of the semiconductor industry, becoming a key bottleneck that hinders the improvement of lithography process yield and restricts the application of advanced processes.
[0048] Example 1
[0049] Based on this, please refer to Figure 2 , Figure 2 This is a schematic diagram of one embodiment of the overlay adjustment device provided in this application, used in a stepper lithography machine. The overlay adjustment device provided in this embodiment includes: an overlay residual measuring device 1, a beam adjuster 2, and a controller 3.
[0050] Specifically, the controller 3 is electrically connected to both the overlay residual measuring device 1 and the beam adjuster 2. The overlay residual measuring device 1 has a built-in sensor and processor. The sensor is responsible for scanning the existing pattern formed on the wafer surface (generating the first scan image) and the projected image of the overlay sample to be exposed (generating the second scan image). The processor accurately calculates the overlay residual data of different regions within a single shot through algorithms such as image registration and deviation comparison, and transmits it to the controller 3 in real time.
[0051] The beam adjuster 2 includes an adjustable lens 21 as a key component for changing the optical path. The change of its tilt angle can directly change the propagation path of the exposure beam. The multi-axis driver 22 has the ability to drive multiple points independently, driving the adjustable lens 21 to achieve complex edge tilting or displacement, ensuring fine control of the optical path.
[0052] The controller 3 receives the overlay residual from the overlay residual measuring device 1, calculates and generates a precise adjustment amount, and drives the multi-axis driver 22 in the beam adjuster 2 to perform the corresponding action. For different overlay error vectors that may occur in different products, the controller 3 supports subdivided adjustments using a built-in recipe, greatly improving the adaptability and accuracy of the device and solving the defect in related technologies where the fixed front glass structure cannot adapt to multiple products.
[0053] It should be understood that, in addition to the aforementioned overlay adjustment device, a stepper lithography machine also includes a sample to be overlaid and a focusing lens group. The sample to be overlaid can be a photomask, with a pattern area ratio of 4:1 to the pattern size of a single exposure unit (Shot) on the wafer. When the exposure light source illuminates the photomask, the pattern information propagates downwards with the beam and is eventually transferred to the exposure plane; the focusing lens group is used to focus the photomask pattern onto the exposure plane. In the embodiments mentioned in this application, the area of the adjustable lens must be no smaller than that of the sample to be overlaid to ensure that all exposure beams carrying the photomask pattern information must pass through the adjustable lens before reaching the focusing lens group.
[0054] The following is in conjunction with the appendix Figure 3 - Appendix Figure 5 The overlay adjustment device used in a stepper lithography machine is described in further detail.
[0055] Please see Figure 3 , Figure 3 This application illustrates a schematic diagram of the optical path alteration principle of the adjustable lens 21. The multi-axis driver 22 moves part of the edge of the adjustable lens 21 up and down, causing the lens to tilt and bend at a preset angle. When the exposure beam passes through the tilted adjustable lens 21, it is refracted due to the difference in refractive index between the air and the lens, causing the optical path to shift. This shift translates into a fine adjustment of the projection position of the photomask pattern on the wafer exposure plane, thereby achieving in-shot overlay compensation.
[0056] like Figure 3 As shown, according to the law of refraction Based on the small-angle approximation relationship of trigonometric functions, the displacement of the exposure beam after passing through the adjustable lens 21 is:
[0057]
[0058] Where i is the incident angle, θ is the refraction angle, n1 is the air refractive index, n2 is the refractive index of the adjustable lens 21, and H is the thickness of the adjustable lens 21.
[0059] In the embodiments mentioned in this application, the air refractive index n1 is 1, the refractive index n2 of the adjustable lens 21 is 1.5, the thickness H of the adjustable lens 21 is 5 mm, and the maximum bending amount is 3‰. According to the formula, the adjustable range of the vector in the wafer pattern is 0 nm to 32.5 nm. It should be understood that the thickness H and refractive index n2 of the adjustable lens 21 can be adaptively selected according to the specific degree of adjustment required in the actual process, and this embodiment does not impose any limitations on this.
[0060] Please see Figure 4 , Figure 4 A schematic diagram showing the specific installation relationship between the multi-axis driver 22 and the adjustable lens 21 provided in this application is shown.
[0061] As shown in Figure 4, the multi-axis actuator 22 includes a support frame (not shown), the outer diameter of which is adapted to a rectangular frame structure. At least eight drive units are fixed on the frame in a uniform and symmetrical manner, covering the entire edge area of the adjustable lens 21, so as to avoid irreversible stress deformation of the lens due to uneven force.
[0062] Furthermore, the control points can be further refined by increasing the number of drive units (e.g., expanding to 12 or 16 axes). Since each drive unit has independent displacement control capabilities, the controller 3 can issue individual displacement commands to any one axis drive unit without affecting the status of other axes.
[0063] Figure 5 The specific structure of the drive unit is shown. The drive unit includes a body 221. The bottom of the body 221 can be fixed to the support frame by any fixing structure or welding to prevent the drive unit from shaking due to machine vibration during operation and causing unexpected compression to the adjustable lens 21. A limiting member 222 is provided on the side wall of the top of the body 221 near the adjustable lens 21.
[0064] Specifically, the limiting member 222 has a receiving space that matches the shape of the edge of the adjustable lens 21, and the edge of the adjustable lens 21 can extend into the receiving space. The limiting member 222 is also provided with an adjusting member (not shown), which can change the volume of the receiving space by rotating the adjusting member. For example, when rotated clockwise, the receiving space shrinks, the clamping force of the limiting member 222 on the edge of the lens increases, and the connection stability between the lens and the drive unit is improved; when rotated counterclockwise, the receiving space expands, the clamping force decreases, and it is convenient for the lens to be disassembled, replaced or initially positioned.
[0065] In some embodiments, to avoid a small natural contact area between the limiting member 222 and the edge of the adjustable lens 21, which could lead to concentrated local clamping force and stress damage to the edge of the adjustable lens 21, the contact area between the limiting member 222 and the edge of the adjustable lens 21 can be appropriately increased, or a flexible contact pad can be provided in the receiving space. The flexible material itself deforms to increase the contact area with the edge of the adjustable lens 21, while buffering local pressure.
[0066] The main body 221 of the drive unit adopts an electric rod structure. When working, the electric rod receives the command issued by the controller 3 and extends and retracts in the direction perpendicular to the exposure plane, driving the limiting member 222 to move up and down synchronously, thereby causing the edge of the adjustable lens 21 to form differentiated displacements at multiple points, realizing the local tilting and surface deformation of the adjustable lens 21.
[0067] Example 2
[0068] This embodiment provides another overlay adjustment device, whose overall system architecture, working principle, and the technical problems it solves are the same as those in Embodiment 1. That is, through the coordinated operation of the overlay residual measuring device 1, the beam adjuster 2, and the controller 3, compensation for the overlay residual within a single exposure unit (Shot) of the stepper lithography machine is achieved. The driving unit includes a body 221 and a limiting member 222 as basic components, and its bottom is also firmly installed on the support frame through a fixing structure or welding method to ensure rigidity.
[0069] Unlike Embodiment 1, which uses an electric pole for vertical telescopic drive, please refer to [link to Embodiment 1]. Figure 6 The main body 221 has an electric slide rail 223 on its side wall facing the adjustable lens 21, and a limiting member 222 is installed on the electric slide rail 223. During operation, the controller 3 sends a command to the electric slide rail 223 to drive the limiting member 222 to move up and down along the slide rail, thereby realizing the local tilt and surface deformation required by the adjustable lens 21.
[0070] The electric slide rail solution provided in this embodiment offers another way to achieve linear displacement for the drive unit. Compared to the electric rod in Embodiment 2, the slide rail structure can achieve higher displacement accuracy, which helps with optical path fine-tuning and meets the overlay compensation requirements within a single exposure unit (Shot).
[0071] Example 3
[0072] This embodiment provides a stepper lithography machine, including the overlay adjustment device as described in Embodiment 1 or Embodiment 2. Figure 7 The optical path diagram of the stepper lithography machine is shown, as follows: Figure 7 As shown, the beam adjuster 2 is installed between the overlay sample 4 and the focusing lens group 5 along the propagation direction of the exposure beam.
[0073] A light source illuminates the overlay sample 4 (i.e., photomask) carrying the chip pattern. The beam of light, carrying the pattern information, propagates downwards. After passing through the adjustable lens 21, the overlay residual measuring device 1 measures the overlay residual and sends it to the controller 3. The controller 3 analyzes and processes the overlay residual to obtain the adjustment amount at each point, and then controls the multi-axis driver 22 (electric lever or electric slide rail) in the beam adjuster 2 to produce the required local tilt or surface deformation at the corresponding point of the adjustable lens 21. When the subsequent exposure beam passes through the calibrated adjustable lens 21 again, it is focused and projects the photomask pattern onto the pattern surface (i.e., the exposure plane) of the wafer, completing the alignment with the original pattern.
[0074] Figure 8 A schematic diagram illustrating the vector transformation of overlay residuals is shown. Figure 8 (b) shows the overlay residual (solid green line) that exists when the beam is not adjusted in a stepper lithography machine. By driving point a upwards and simultaneously driving point e downwards via the multi-axis driver 22 according to instructions, the adjustable lens 21 produces... Figure 8 The tilting deformation shown in (a) alters the optical paths at points a and e (the solid red line in the figure represents the new optical path after adjustment, and the dashed line represents the original optical path), thereby fine-tuning the projection position of the photomask pattern. The adjusted overlay vector is as follows: Figure 8 As shown in (c), the overlay residual is significantly reduced, and the remaining linear translational shift can be compensated for by controlling the wafer stage. After this step, the overlay residual is finally corrected, as shown in the image. Figure 8 As shown in (d) in the figure.
[0075] Figure 9 A schematic diagram illustrating the vector transformation of overlay residuals is shown. Figure 9 Figure (b) illustrates the overlay residuals present when the beam is not adjusted in a stepper lithography machine. By using a multi-axis driver 22 to drive points a and c upwards and simultaneously drive points e and g downwards according to instructions, the adjustable lens 21 can produce an effect similar to... Figure 9 The tilting deformation shown in (a) alters the optical paths at points a, c, e, and g, thereby fine-tuning the projection position of the photomask pattern. The adjusted overlay vector is as follows: Figure 9 As shown in (c), the overlay residual is significantly reduced, and the remaining linear translational shift can be compensated for by controlling the wafer stage. After this step, the overlay residual is finally corrected, as shown in the image. Figure 9 As shown in (d) in the figure.
[0076] The stepper lithography machine and the overlay adjustment device for the stepper lithography machine provided in this application have the following unexpected technical effects:
[0077] Compared to the fixed front glass solution in the prior art, this application provides an overlay adjustment device consisting of an overlay residual measuring device, an adjustable lens and a multi-axis driver, which realizes accurate compensation for overlay residuals within a single exposure unit (Shot).
[0078] Under the control of a multi-axis driver, the adjustable lens can produce local tilting and surface deformation at its edges, altering the optical path of the beam passing through the adjustable lens. This compensates for the overprinting residuals between the projected position and the ideal position of the photomask pattern, effectively solving the problem that fixed structures cannot adapt to multi-variety production. Furthermore, to address the potential for different overprinting residuals on the same machine, the controller can have built-in recipes for finer adjustments to different products, enhancing the flexibility and adaptability of the device.
[0079] Compared to the expensive customized processing in related technologies, the overlay adjustment device provided in this application can save about one million yuan in costs per process, which is economically significant and provides key technical support for improving the yield and large-scale application of advanced semiconductor processes.
[0080] Please note that the above embodiments are for illustrative purposes only and do not imply any limitation on the present invention.
[0081] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0083] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. An overlay adjustment device for a stepper lithography machine, characterized in that, include: Overlay residual measuring instrument, used to obtain the overlay residual of the overlay sample to be tested; A beam adjuster, located directly below the overlay sample under test, includes: an adjustable lens and a multi-axis driver; the multi-axis driver is used to drive the adjustable lens to move along multiple points to generate a preset angle of curvature, so as to change the position of the overlay sample under test projected on the exposure plane. The controller, connected to the overlay residual measuring device and the beam adjuster, is used to generate an adjustment amount upon receiving the overlay residual and drive the multi-axis driver to perform the corresponding action.
2. The overlay adjustment device according to claim 1, characterized in that, The multi-axis drive includes a support frame and at least eight drive units evenly and symmetrically arranged on the support frame; wherein each drive unit has an independent stroke.
3. The overlay adjustment device according to claim 2, characterized in that, The drive unit includes a body, with a limiting member on the top sidewall of the body and the bottom end fixedly mounted on the support frame; the limiting member is used to press against the edge of the adjustable lens. The limiting member is also provided with an adjusting member. Rotating the adjusting member can adjust the magnitude of the clamping force applied by the limiting member to the edge of the adjustable lens.
4. The overlay adjustment device according to claim 3, characterized in that, The main body includes an electric pole; Driven by the controller, the electric rod extends and retracts in a direction perpendicular to the exposure plane, so that the adjustable lens bends independently at multiple points.
5. The overlay adjustment device according to claim 3, characterized in that, The main body has an electric slide rail on its side wall facing the adjustable lens, and the limiting member is mounted on the electric slide rail; The electric slide rail is electrically connected to the controller; it is used to drive the limiting member to slide up and down along the electric slide rail so that the adjustable lens can bend independently at multiple points.
6. The overlay adjustment device according to claim 1, characterized in that, The overlay residual measuring instrument includes: A sensor is used to scan the wafer pattern and the corresponding image of the overlay sample to be tested on the exposure plane to obtain a first scan image and a second scan image. A processor is configured to generate the overlay residual upon receiving the first scanned image and the second scanned image.
7. The overlay adjustment device according to any one of claims 1-6, characterized in that, The adjustable lens bends no more than 3‰ at each point.
8. The overlay adjustment device according to any one of claims 1-6, characterized in that, The area of the adjustable lens is not less than the area of the overlay sample to be tested.
9. The overlay adjustment device according to claim 8, characterized in that, The ratio of the area of the overlay sample to the size of the wafer pattern is 4:
1.
10. A stepper lithography machine, characterized in that, Includes the overlay adjustment device as described in any one of claims 1-9.