Method and system for adjusting deformation of photomask

Abstract

The invention discloses a method and a system for adjusting deformation of a photomask, and aims to improve the accuracy of a lithography process which is crucial to semiconductor manufacturing. The method involves projecting structured light onto a reticle to capture a reference image before the reticle contacts the wafer. If this reference image, referred to as the first image, is not pre-stored, the system captures it by projecting structured light onto the surface of the reticle. Then, a wafer is placed on the bearing table, and the bearing table is moved to the position below the photomask; the upward movement of the carrier brings the wafer into contact with the photomask, thereby forming a convex pattern representing deformation as a second image. The difference between the first and second images is analyzed by the arithmetic device to guide the adjustment of the carrier to ensure that the deformation of the photomask is maintained within a predetermined range.

Description

Technical Field

[0001] A detection and adjustment method, in particular a method and system for adjusting mask deformation. Background Art

[0002] Photolithography is an important step in the semiconductor device manufacturing process. This step uses exposure and development to depict geometric structures on the photoresist layer, and then uses an etching process to transfer the pattern on the mask to the substrate or wafer.

[0003] The lithography process also includes contact lithography, which is a method of moving the wafer to make it contact with the mask and then performing exposure to form a pattern on the wafer. Figure 1A and Figure 1B , Figure 1A and Figure 1B The diagram shows a schematic diagram of contact lithography. Figure 1A , the mask 14 is placed on the support 13, and the wafer 12 is located below the mask 14 and placed on the carrier 11. Figure 1B , the carrier 11 is lifted upwards, so that the wafer 12 contacts the lower surface of the mask 14 , and the upper surface 14 a of the mask 14 can be exposed.

[0004] However, ideally, the wafer 12 is in complete contact with the plane of the mask 14, but in practice, there is often an error when moving the carrier 11. Figure 1C and Figure 1D , Figure 1C and Figure 1D The diagram shows the deformation of the mask caused by contact error. Figure 1C In the process, the carrier 11 cannot maintain a precise level when rising, so that the wafer 12 on one side rises excessively and squeezes the mask 14, causing the mask 14 to deform, and the wafer 12 on the other side cannot contact the mask 14. Figure 1D In the example, the carrier 14 rises too far, causing the wafer 12 to press against the mask 14, deforming it. However, if the mask 14 is deformed or if part of the wafer 12 is not in contact with the mask 14, imaging distortion may occur during exposure, resulting in an undesirable pattern on the wafer.

[0005] In the past, in processes with resolutions above 5 microns, the errors introduced by the movable stage 11 were within acceptable limits, so adjustment of the movable stage 11 was unnecessary. However, with the increasing sophistication of processes, especially in processes with resolutions below 2 microns, the yield reduction caused by the errors introduced by the movable stage 11 is often unacceptable. Currently, manual adjustment of the stage 11 is often required to ensure that the wafer 12 is in level contact with the photomask 14. However, manual adjustment relies heavily on experience and can still be unreliable.

[0006] Therefore, how to solve the above problems is something that people with general knowledge should consider. Summary of the Invention

[0007] In view of the above problems, the present invention provides a method and system for adjusting mask deformation to precisely detect, quantify and correct mask deformation, thereby solving a major challenge in semiconductor production.

[0008] The present invention provides a method for adjusting mask deformation, comprising:

[0009] (a) checking whether a first image is stored, the first image being an image of a structured light irradiated on a surface of a photomask before the photomask contacts a wafer; if not, irradiating the photomask with the structured light and capturing an image of a pattern formed by the structured light on the surface of the photomask as the first image;

[0010] (b) placing a wafer on a carrier and moving the carrier under a photomask;

[0011] (c) moving the carrier upward so that the wafer contacts the photomask, so that a convex pattern is formed on the surface of the photomask close to the structured light, and capturing an image formed by the structured light on the surface of the photomask as a second image;

[0012] (d) comparing the first image and the second image using a computing device; and

[0013] (e) The computing device adjusts the supporting platform according to the difference between the first image and the second image so that the deformation of the mask is smaller than a predetermined range.

[0014] The present invention provides a system for adjusting mask deformation, which is used to detect whether a mask is deformed. The system for adjusting mask deformation includes:

[0015] a structured light source, adapted to generate structured light and irradiate the structured light onto the surface of the light mask; an image capturing device, adapted to capture an image of the structured light irradiated on the surface of the light mask; and

[0016] a computing device electrically connected to the image capturing device;

[0017] The image capturing device is configured as follows:

[0018] Before the mask contacts a wafer, storing an image of the structured light irradiated on the surface of the mask as a first image;

[0019] After the mask contacts the wafer and a convex pattern is formed on the mask, an image of the structured light irradiated on the surface of the mask is stored as a second image;

[0020] Wherein, the wafer is placed on a carrier;

[0021] The computing device adjusts the height of the supporting platform according to the difference between the first image and the second image, so that the deformation of the mask is smaller than a predetermined range.

[0022] In the method for adjusting the deformation of the mask of the present invention, one of the steps is to project structured light onto the surface of the mask to establish a reference for deformation measurement. This step involves checking whether there is a previously stored image, called the first image, which represents the pattern formed on the mask by the structured light before contacting the wafer. If this image has not been stored, the system continues to project the structured light onto the mask and captures this critical reference image. Subsequently, a wafer is placed on the carrier and then moved under the mask. The carrier is lifted to force the wafer into contact with the mask, forming a convex pattern representing the deformation of the mask at the interface illuminated by the structured light.

[0023] To assess the degree of deformation, a second image of the raised pattern formed after contact is captured and directly compared to the first reference image. An algorithm plays a key role in analyzing the differences between these two images, effectively quantifying the deformation. Based on this analysis, the algorithm adjusts the support platform to ensure that the deformation of the mask remains within a predetermined acceptable range. This adjustment is crucial for accurate pattern transfer during the photolithography process, ultimately contributing to the production of high-quality semiconductor devices.

[0024] In one embodiment, stripe light is used as structured light, and the structured light can be generated in different ways, such as by projecting light through a grating or using a spatial light modulator.

[0025] The present invention's system for adjusting reticle deformation includes a structured light source capable of generating the desired structured light pattern, an imaging device for capturing images of these structured light patterns on the reticle, and a computing device for analyzing the captured images and controlling adjustments to the support platform. Through the detailed processes involved in structured light projection, image capture, and computational analysis, the present invention significantly improves the accuracy and reliability of the lithography process, thereby advancing the field of semiconductor device manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A and Figure 1B Shown is a schematic diagram of contact lithography;

[0027] Figure 1C and Figure 1D The diagram depicts a schematic diagram of the deformation of the mask due to contact error in contact lithography;

[0028] Figure 2 The diagram shows a method for detecting and adjusting the deformation of the mask 14 according to the present invention;

[0029] Figure 3A The diagram shows the configuration of the structured light source and the light mask;

[0030] Figure 3B The illustrated embodiment is a mask deformation detection system 100 according to the first embodiment;

[0031] Figure 3C The illustrated embodiment is a mask deformation detection system 200 according to the second embodiment;

[0032] Figure 4A The diagram shown is a schematic diagram of the mask 14 before deformation;

[0033] Figure 4B FIG. 1 is a schematic diagram of the mask 14 after deformation.

[0034]

Explanation of symbols

[0035] 11: Carrying platform

[0036] 12: Wafer

[0037] 13: Bracket

[0038] 14: Mask

[0039] 14a: Upper surface

[0040] 14b: Lower surface

[0041] 14c: convex pattern

[0042] 100, 200: Mask deformation detection system

[0043] 110, 210: Structured light source

[0044] 111, 211: light source

[0045] 112: Raster

[0046] 120: Structured Light

[0047] 121: First Image

[0048] 122: Second Image

[0049] 130: Image capture device

[0050] 140: Computing device

[0051] 150: Storage device

[0052] 212: Spatial Light Modulator

[0053] S10~S80: Flowchart steps DETAILED DESCRIPTION

[0054] See also Figure 2 、 Figure 3A and Figure 3B , Figure 2 The diagram shows the method of adjusting the mask deformation of the present invention. Figure 3A The diagram shows the configuration of the structured light source and the light mask. Figure 3B The diagram shows a first embodiment of a mask deformation detection system. The mask deformation detection system 100 includes a structured light source 110, an image capturing device 130, a computing device 140, and a storage device 150. First, step S10 is performed to determine whether the storage device 150 stores an image of the mask 14 and the wafer 12 before the contact is made by the structured light irradiated on the surface of the mask 14, hereinafter referred to as the first image 121 (e.g., Figure 4A If not, then step S15 is performed, using the structured light source 110 to illuminate the surface of the mask 14 opposite to the wafer 12, so that the first image 121 formed by the structured light 120 after illuminating the mask 14 is stored in the storage device 150. If yes, then the subsequent step is performed, that is, step S20. In this embodiment, the structured light 120 is a stripe light, which can form a plurality of stripe patterns 121 on the upper surface 14a of the mask 14, as shown. Figure 3B 、 Figure 3C and Figure 4A However, the structured light 120 pattern may also be a grid, a dot array, or a coded pattern, and the color of the structured light may also be black and white, grayscale, or color. Figure 3B In the first embodiment, the structured light source 110 includes a light source 111 and a grating 112. The structured light 120 is formed by irradiating the grating 112 with the light source 111. That is, the structured light 120 formed after the light passes through the grating 112 forms a first image 121 corresponding to the grating 112 on the surface of the mask 14. Figure 3CIn the second embodiment, the structured light source 210 includes a light source 211 and a spatial light modulator 212. The light source 211 illuminates the spatial light modulator 212, whereupon the spatial light modulator 212 modulates the light to form the structured light 120. The spatial light modulator 212 may be, for example, a digital micromirror device (DMD) or a liquid crystal on silicon (LCoS) device, and may form the structured light 120 through transmission modulation or reflection modulation, thereby forming a corresponding first image 121 on the mask 14.

[0055] Next, please continue to refer to Figure 2 In step S20, the wafer 12 is placed on the carrier 11, and the carrier 11 is moved to the bottom of the mask 14. That is, the wafer 12 is placed under the mask 14 by the carrier 11, which is equivalent to Figure 1A In addition, the photomask 14 is placed on the photomask carrier 13. Then, step S30 is performed to move the carrier 11 upward so that the wafer 12 contacts the photomask 14. In other words, the purpose of step S30 is to make the surface to be exposed on the wafer 12 contact the photomask 14, which is equivalent to Figure 1B or states 1C, 1D. Moreover, the image capture device 130 continuously captures the upper surface 14a of the mask 14 during this step to observe whether the mask 14 is deformed. In this embodiment, the image capture device 130 can capture the upper surface 14a of the mask 14 at short time intervals. Alternatively, the computing device 140 can estimate the time required for the wafer 12 to rise based on the distance between the wafer 12 and the mask 14 and the rising speed of the carrier 11, and command the image capture device 130 to capture the upper surface 14a of the mask 14 after the time required for the rise has elapsed. In the latter case, it is possible that the wafer 12 does not touch the mask 14 after rising. In this case, fine-tuning can be initiated until the upper surface 14a of the mask 14 is deformed.

[0056] Next, step S40 is performed. When it is detected that the upper surface 14a of the mask 14 forms a convex pattern 14b (e.g. Figure 4BAs shown), the image formed by the structured light 10 irradiating the upper surface 14a of the mask 4 is captured and stored as a second image 122. Next, step S50 is executed, and the computing device 140 is further used to compare the first image 121 with the second image 122. In other words, the pattern difference before and after the mask 14 contacts the wafer 12 is compared to determine the degree of deformation of the mask 14. Next, step S60 is executed, and according to the degree of deformation of the mask 14 calculated by the computing device 140, the computing device 140 controls and adjusts the carrier 11 so that the deformation of the mask 14 is less than a predetermined range. Thereafter, step S65 is executed, and the computing device 140 determines whether the deformation of the mask 14 is within an acceptable range (i.e., less than or equal to a predetermined range). If it is within an acceptable range, the computing device 140 stops adjusting the height of the carrier 11 (as shown in step S70). Otherwise, the height of the carrier 11 is continuously adjusted until the computing device 140 determines that the deformation of the mask 14 is within an acceptable range (as shown in step S80). Then, the subsequent lithography process can be carried out.

[0057] In one embodiment, in steps S50 and S60, the computing device 140 adjusts the carrier 11 based on the known dimensions of the wafer 12 and the degree of deformation of the reticle 14. Specifically, the storage device 150 stores information such as the dimensions, materials, and material mechanics of the wafer 12 and reticle 14. By comparing the first image 121 with the second image 122, the computing device 140 can infer whether the wafer 12 is flat or tilted, and to what extent, thereby calculating how to adjust the carrier 11 to keep the deformation of the reticle 14 within a predetermined range. Furthermore, the carrier 11 is vertically moved by a plurality of linear motion devices (at least three) controlled by the computing device 140. In steps S60 and S80, the carrier 11 is adjusted by controlling the height positions of these linear motion devices.

[0058] Through the above steps S10 to S80 , the contact state between the wafer 12 and the mask 14 can be effectively determined and adjusted, and the height of the carrier 11 can be controlled to ensure good contact between the wafer 12 and the mask 14 , thereby improving the accuracy of subsequent exposure.

[0059] The above description of the present invention is not intended to limit the scope of the patent rights claimed by the present invention. The scope of patent protection shall be determined by the appended claims and their equivalents. Any changes or modifications made by persons skilled in the art that do not depart from the spirit or scope of this patent shall be considered equivalent changes or designs achieved within the spirit of this invention and shall be included in the claims.

Claims

1. A method for adjusting mask deformation, characterized in that: include: (a) checking whether a first image is stored, the first image being an image of a structured light irradiated on a surface of a photomask before the photomask contacts a wafer; if not, irradiating the photomask with the structured light and capturing an image of a pattern formed by the structured light on the photomask surface as the first image; (b) placing a wafer on a carrier and moving the carrier under a photomask; (c) moving the carrier upward so that the wafer contacts the photomask, so that a convex pattern is formed on the surface of the photomask close to the structured light, and capturing an image formed by the structured light on the surface of the photomask as a second image; (d) comparing the first image and the second image using a computing device; and (e) The computing device adjusts the supporting platform according to the difference between the first image and the second image so that the deformation of the mask is smaller than a predetermined range.

2. The method for adjusting mask deformation according to claim 1, wherein: The structured light is a stripe of light.

3. The method for adjusting mask deformation according to claim 1 or claim 2, wherein: The structured light is generated by irradiating a light source onto a grating.

4. The method for adjusting mask deformation according to claim 1 or claim 2, wherein: The structured light is generated by irradiating a light source onto a spatial light modulator and then being modulated by the spatial light modulator.

5. A system for adjusting mask deformation, characterized in that: A system for detecting whether a photomask is deformed and adjusting the photomask deformation includes: a structured light source, adapted to generate structured light and irradiate the structured light onto the surface of the light mask; an image capturing device adapted to capture an image of the structured light irradiated on the surface of the light mask; and a computing device electrically connected to the image capturing device; The image capturing device is configured as follows: Before the mask contacts a wafer, storing an image of the structured light irradiated on the surface of the mask as a first image; After the mask contacts the wafer and a convex pattern is formed on the mask, an image of the structured light irradiated on the surface of the mask is stored as a second image; Wherein, the wafer is placed on a carrier; The computing device adjusts the height of the supporting platform according to the difference between the first image and the second image, so that the deformation of the mask is smaller than a predetermined range.

6. The system for adjusting mask deformation according to claim 5, wherein: The structured light source includes a light source and a grating, and the structured light is generated by irradiating a light source onto a grating.

7. The system for adjusting mask deformation according to claim 5 or claim 6, wherein: The structured light is a stripe of light.

8. The system for adjusting mask deformation according to claim 5, wherein: The structured light source includes a light source and a spatial light modulator, wherein the structured light is generated by irradiating a light source onto the spatial light modulator and then being modulated by the spatial light modulator.

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