Method for repairing defects of a photomask

Abstract

The application provides a mask defect repairing method, and relates to the technical field of semiconductors, which comprises the following steps: firstly, determining the position of a defect on a mask; then, forming a resist layer on the surface of the defect, wherein the resist layer covers the defect; subsequently, forming a photoresist layer, wherein the photoresist layer is distributed around the resist layer, and the photoresist layer and the resist layer have non-adhesion; and then, etching the resist layer and the defect by taking the photoresist layer as a mask to remove the resist layer and the defect. Since the photoresist layer and the resist layer have non-adhesion, the surface of the resist layer will not form the photoresist layer in the process of forming the photoresist layer, and the photoresist layer is formed around the resist layer, so that the photoresist layer can be directly taken as a mask to etch the resist layer and the defect after the photoresist layer is formed, thereby removing the resist layer and the defect, simplifying the mask repairing process, avoiding secondary exposure, baking and developing process after exposure, shortening the mask repairing period, and improving the repairing precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a defect repair method of a photomask. BACKGROUND

[0002] In the semiconductor manufacturing process, the photolithography process is a key link to determine the performance and integration of chips, and the quality of the photomask as a pattern transfer template in the photolithography process directly affects the precision of photolithography and the yield of chips. With the continuous development of semiconductor technology, the feature size of chips is continuously reduced, and the precision and defect control requirements of photomasks are also increasingly high. Due to various reasons such as uneven photoresist coating, exposure energy fluctuation, etching process deviation, and particle pollution in the environment, defects will inevitably occur in the photomask during manufacturing and use. These defects include but are not limited to excess material in transparent areas (black defects), missing material in light-shielding areas (white defects), and irregular edges of patterns, etc. If the defects on the photomask cannot be effectively repaired, these defects will be copied to the photoresist layer on the wafer during the photolithography process, thereby causing short circuits, open circuits, inconsistent device performance, and other problems in the chip manufacturing process, which seriously reduces the yield of chips and increases the manufacturing cost.

[0003] However, in the current photomask defect repair process, the following problems exist: (1) low repair precision: although laser repair is fast, the laser energy is difficult to accurately control, which easily causes thermal damage to other areas of the photomask, affecting the optical performance and pattern precision of the photomask. (2) Low repair efficiency: ion beam milling can achieve high-precision material removal, but the device is complex, the cost is high, and the repair efficiency is low. (3) Poor repair compatibility: chemical vapor deposition may have problems such as poor adhesion of the deposited material and poor compatibility with the photomask material when repairing defects, resulting in the reappearance of defects in the photomask after repair during subsequent use. (4) Complex repair process: the secondary exposure process is long, occupies more machine capacity, has a long repair cycle, increases production cost, and the precision needs to be improved. SUMMARY

[0004] The purpose of the present application is to provide a defect repair method of a photomask to repair photomask defects, simplify the photomask repair process, and reduce the difficulty of photomask repair.

[0005] To achieve the above purpose, the present application provides a defect repair method of a photomask, comprising: providing a photomask; determining the position of a defect in the photomask; forming a resist layer on the surface of the defect, the resist layer covering the defect; forming a photoresist layer on the photomask, the photoresist layer being distributed around the resist layer, and the photoresist layer and the resist layer having non-adhesion therebetween; etching the resist layer and the defect with the photoresist layer as a mask to remove the resist layer and the defect.

[0006] Optionally, in the method for repairing defects of a photomask, the material of the resist layer is polydimethylsiloxane.

[0007] Optionally, in the method for repairing defects of a photomask, the forming method of the resist layer comprises: forming an uncured resist material layer on the defect by a point-by-point process; and baking the resist material layer to cure the resist material layer and form the resist layer.

[0008] Optionally, in the method for repairing defects of a photomask, when the resist material layer is baked, the baking temperature is 90-130°C, and the baking time is 10-25 minutes.

[0009] Optionally, in the method for repairing defects of a photomask, the photomask comprises a light-transmitting substrate and a patterned light-blocking layer on the surface of the light-transmitting substrate, the patterned light-blocking layer exposes part of the surface of the light-transmitting substrate, and the defect is located on the exposed surface of the light-transmitting substrate.

[0010] Optionally, in the method for repairing defects of a photomask, the top surface of the resist layer is higher than the top surface of the patterned light-blocking layer.

[0011] Optionally, in the method for repairing defects of a photomask, the photoresist layer is formed by a spin coating process, the photoresist layer covers the patterned light-blocking layer and covers the exposed surface of the light-transmitting substrate.

[0012] Optionally, in the method for repairing defects of a photomask, after the resist layer and the defect are etched, the method for repairing defects of a photomask further comprises: performing a cleaning process to remove the remaining photoresist layer on the photomask.

[0013] Optionally, in the method for repairing defects of a photomask, the resist layer and the defect are etched by a dry etching process to remove the resist layer and the defect.

[0014] Optionally, in the method for repairing defects of a photomask, the material of the photoresist layer is phenolic resin.

[0015] In the method for repairing defects of a photomask provided by the application, the position of a defect in the photomask is determined first; then a resist layer is formed on the surface of the defect, and the resist layer covers the defect; then a photoresist layer is formed, the photoresist layer is distributed around the resist layer, and the photoresist layer and the resist layer have non-adhesion; then the resist layer and the defect are etched with the photoresist layer as a mask to remove the resist layer and the defect. Since the photoresist layer and the resist layer have non-adhesion, the surface of the resist layer will not form a photoresist layer in the process of forming the photoresist layer, therefore, the photoresist layer is formed around the resist layer, and after the photoresist layer is formed, the photoresist layer can be directly used as a mask to etch the resist layer and the defect without the processes of exposure, baking after exposure and development, so as to remove the resist layer and the defect. The photomask repairing process is simplified, the difficulty of photomask repairing is reduced, the photomask is not exposed twice, the photomask repairing period is shortened, and the repairing precision is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 FIG. 1 is a flowchart of a method for repairing defects of a photomask provided by an embodiment of the application.

[0017] Figure 2 FIG. 2 is a structural cross-sectional view of a photomask in the method for repairing defects of a photomask provided by an embodiment of the application.

[0018] Figure 3 FIG. 3 is a structural cross-sectional view after a resist layer is formed in the method for repairing defects of a photomask provided by an embodiment of the application.

[0019] Figure 4 FIG. 4 is a structural cross-sectional view after a photoresist layer is formed in the method for repairing defects of a photomask provided by an embodiment of the application.

[0020] Figure 5 FIG. 5 is a structural cross-sectional view after a defect is removed in the method for repairing defects of a photomask provided by an embodiment of the application.

[0021] Figure 6 FIG. 6 is a structural cross-sectional view after a cleaning process is performed in the method for repairing defects of a photomask provided by an embodiment of the application.

[0022] In the figures, the reference signs are explained as follows: 100-photomask; 100a-defect; 101-transparent substrate; 102-patterned light shielding layer; 110-resist layer; 120-photoresist layer. DETAILED DESCRIPTION

[0023] The method for repairing defects of a photomask according to the embodiments of the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present application will be more apparent according to the following description. It should be noted that the accompanying drawings are very simplified and use non-precise proportions, which are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application. In addition, the structures shown in the accompanying drawings are often a part of the actual structures. In particular, the emphasis of each drawing is different, and sometimes different proportions are used.

[0024] Figure 1 is a flowchart of the method for repairing defects of a photomask according to the embodiments of the present application. As shown in Figure 1 , the present embodiment provides a method for repairing defects of a photomask, which comprises: step S1, providing a photomask; step S2, determining the position of a defect in the photomask; step S3, forming a resist layer on the surface of the defect, the resist layer covering the defect; step S4, forming a photoresist layer on the photomask, the photoresist layer being distributed around the resist layer, and the photoresist layer and the resist layer having non-adhesion therebetween; and step S5, etching the resist layer and the defect with the photoresist layer as a mask to remove the resist layer and the defect.

[0025] Figure 2 is a structural cross-sectional view of the photomask in the method for repairing defects of a photomask according to the embodiments of the present application. Figure 3 is a structural cross-sectional view after forming a resist layer in the method for repairing defects of a photomask according to the embodiments of the present application. Figure 4 is a structural cross-sectional view after forming a photoresist layer in the method for repairing defects of a photomask according to the embodiments of the present application. Figure 5 is a structural cross-sectional view after removing a defect in the method for repairing defects of a photomask according to the embodiments of the present application. Figure 6 is a structural cross-sectional view after performing a cleaning process in the method for repairing defects of a photomask according to the embodiments of the present application. The method for repairing defects of a photomask according to the present embodiment will be described in more detail below with reference to the accompanying drawings and specific embodiments. Figures 2-6

[0026] First, as shown in Figure 2 , step S1 is performed to provide a photomask 100. The photomask 100 is used to transfer a pattern onto a semiconductor structure.

[0027] Specifically, the photomask 100 comprises a light-transmitting substrate 101 and a patterned light-blocking layer 102 on the surface of the light-transmitting substrate 101, and the patterned light-blocking layer 102 exposes part of the surface of the light-transmitting substrate 101.

[0028] ​The light-transmitting substrate 101 is used to allow light to pass through the photomask 100 when transferring patterns, so as to transfer the patterns onto the photoresist layer of the semiconductor structure. The material of the light-transmitting substrate 101 is glass, quartz, or silicon dioxide.

[0029] The patterned light-shielding layer 102 is used to block areas that do not require exposure during the photolithography process, ensuring that only specific patterns are transmitted through the light-transmitting areas to the photoresist layer of the semiconductor structure. The material of the patterned light-shielding layer 102 is chromium.

[0030] Next, step S2 is executed to determine the location of the defect 100a in the photomask 100, that is, to determine the defect area of ​​the photomask 100. The defect 100a on the photomask 100 is, for example, a pinhole, a scratch, or metal residue (such as metal residue generated by etching in the previous process). In this embodiment, the defect 100a is a metal residue, such as chromium residue, which is opaque and thus affects the light transmittance of the light-transmitting substrate. The defect 100a is located on the exposed surface of the light-transmitting substrate 101.

[0031] Specifically, the method for determining the location of the defect 100a in the photomask 100 includes: using a high-resolution optical inspection system or electron beam inspection equipment to perform a full-area scan of the photomask 100, thereby determining whether the photomask 100 has a defect 100a, and acquiring information about the defect 100a, including its coordinates, size, and type, thereby determining the location of the defect 100a on the photomask 100. The type of defect may, for example, be a metal residue.

[0032] In addition, the thickness (or height) data of defect 100a can also be obtained.

[0033] Next, as Figure 3 As shown, in step S3, a resist layer 110 is formed on the surface of the defect 100a. The resist layer 110 covers the defect 100a, that is, the resist layer 110 covers the top surface and side surface of the defect 100a. After the resist layer 110 is formed, the exposed surfaces of the patterned light-shielding layer 102 and the light-transmitting substrate 101, except for the area where the defect 100a is located, are exposed.

[0034] In the embodiment, the resist blocking layer 110 has the function of blocking the photoresist layer 120, so that the resist blocking layer 110 and the photoresist layer 120 formed subsequently have non-adhesion, that is, the interface affinity between the resist blocking layer 110 and the photoresist layer 120 formed subsequently is very low, and the top surface of the resist blocking layer 110 is difficult to coat the photoresist layer 120. In the process of forming the photoresist layer subsequently, the photoresist can be prevented from being coated on the surface of the defect 100a, so as to avoid affecting the subsequent defect etching.

[0035] In the embodiment, the material of the resist blocking layer 110 is polydimethylsiloxane (PDMS). The forming method of the resist blocking layer 110 includes: first, forming an uncured resist blocking material layer on the defect 100a by a fixed-point process, so that the resist blocking material layer is formed on the surface of the defect 100a, thereby reducing or avoiding the resist blocking material layer from being coated on the non-defect area; wherein the probe station and the micropipette device can be combined to form the uncured resist blocking material layer, so as to realize the fixed-point deposition of the resist blocking material layer, that is, the micropipette is first fixed on the microoperator of the probe station, and the uncured resist blocking material is drawn, then the microscope of the probe station is positioned to the position of the defect 100a on the mask 100 as the deposition site, and the microoperator is finely adjusted to align the tip of the micropipette to the position of the defect 100a, so as to inject the resist blocking material into the position where the defect 100a is located, thereby forming the uncured resist blocking material layer.

[0036] Further, in the process of forming the resist blocking material layer, the thickness of the resist blocking material layer can be adjusted according to the thickness of the defect 100a, so that the thickness of the resist blocking material layer is greater than the thickness of the defect 100a, and the difference between the thickness of the resist blocking material layer and the thickness of the defect 100a can be ≤100 nm, for example, the thickness difference between the thickness of the resist blocking material layer and the thickness of the defect 100a can be 50 nm-90 nm, so as to avoid that the resist blocking material layer is too thick to affect the original pattern of the mask, thereby avoiding that the resist blocking material layer covers the non-defect area (or non-defect position), and further avoiding affecting the original pattern of the mask 100, and avoiding the problem that the resist blocking material layer is too thin to completely cover the defect.

[0037] Then, the resist blocking material layer is baked to cure the resist blocking material layer and form the resist blocking layer 110. When the resist blocking material layer is baked, the mask can be placed on a hot plate, so as to realize the baking of the resist blocking material layer.

[0038] In the embodiment, when the resist blocking material layer is baked, the baking temperature is 90°C-130°C, for example, 100°C, 105°C, 110°C, 115°C or 125°C, etc.; and the baking time is 10 min-25 min.

[0039] In this embodiment, the top surface of the resist layer 110 may be higher than the top surface of the patterned light-shielding layer 102 to ensure that the resist layer 110 completely covers the defect 100a. During the subsequent formation of the photoresist layer, the defect 100a will be completely covered by the resist layer, preventing the surface of the defect 100a from being exposed, thereby preventing the photoresist layer from affecting the subsequent defect etching process.

[0040] Furthermore, when forming the resist layer 110, the resist layer 110 also covers part of the surface of the light-transmitting substrate 101 around the defect 100a, so as to ensure that the defect 100a is completely covered by the resist layer 110.

[0041] Next, as Figure 4 As shown, a photoresist layer 120 is formed on the photomask 100. The photoresist layer 120 is distributed around the resist layer 110, that is, the photoresist layer 120 surrounds the resist layer 110, and the photoresist layer 120 and the resist layer are non-adhesive. Because the photoresist layer 120 and the resist layer are non-adhesive, the top surface of the resist layer 110 will not form the photoresist layer 120 during the formation of the photoresist layer 120. Therefore, the photoresist layer 120 is formed around the resist layer 110. Thus, after the formation of the photoresist layer 120, there is no need to perform exposure, baking, and development processes on the photoresist layer 120. The photoresist layer 120 can be directly used as a mask to etch the resist layer 110 and the defect 100a, avoiding secondary exposure of the photomask 100.

[0042] In this embodiment, the photoresist layer 120 is made of phenolic resin, so that the photoresist layer 120 has high polarity and extremely low interfacial affinity with the resist layer 110. It is difficult to coat the top surface of the resist layer 110 with photoresist. Therefore, during the formation of the photoresist layer 120, there is no photoresist layer 120 on the top surface of the resist layer 110.

[0043] Specifically, the photoresist layer 120 can be formed by spin coating, and then the photoresist layer 120 can be subjected to a soft baking process at a temperature of 90℃~120℃.

[0044] In this embodiment, the photoresist layer 120 covers the patterned light-shielding layer 102 and the exposed surface of the light-transmitting substrate 101. That is, the photoresist layer 120 also covers the portion of the surface of the light-transmitting substrate 101 that is not covered by the resist layer 110, so as to avoid damaging the light-transmitting substrate 101 in subsequent etching processes.

[0045] The top surface of the photoresist layer 120 may be higher than the top surface of the resist layer 110. The thickness of the photoresist layer 120 may be, for example, 3000 angstroms.

[0046] Next, as Figure 5 As shown, in step S5, using the photoresist layer 120 as a mask, the resist layer 110 and the defect 100a are etched to remove them. Since the material of the resist layer 110 is different from that of the photoresist layer 120, there is a high etching selectivity between them. Therefore, during the etching process, only the resist layer 110 and the defect 100a can be etched, thereby removing them. In this embodiment, after the photoresist layer 120 is formed, there is no need for further exposure, baking, and development processes. The photoresist layer 120 can be directly used as a mask to etch the resist layer 110 and the defect 100a, thereby removing them. The restoration process for photomask 100 has been simplified, the restoration difficulty has been reduced, secondary exposure of photomask 100 has been avoided, the restoration cycle of photomask 100 has been shortened, and the restoration accuracy has been improved.

[0047] In this embodiment, the resist layer 110 and the defect 100a are etched using a dry etching process to remove the resist layer 110 and the defect 100a. The etching gas used in the dry etching process includes chlorine and oxygen.

[0048] Next, as Figure 6 As shown, after etching the resist layer and the defect, the process further includes: performing a cleaning process to clean the etched photomask 100 to remove the remaining photoresist layer on the photomask 100 and to remove the resist layer residue on the surface of the photomask.

[0049] Specifically, firstly, the photomask 100 is cleaned using a combination of ultrasonic cleaning and megasonic cleaning processes; concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) can be used as cleaning solutions in the ultrasonic cleaning and megasonic cleaning processes. Then, the photomask 100 is dried, for example by spin drying, to remove water marks and other impurities.

[0050] Next, the photomask 100 is inspected. For example, the transmittance and reflectance of the area where the repaired defect 100a is located are inspected by a photomask inspection system to see if they meet the preset standards.

[0051] In summary, the defect repair method for photomasks provided by this invention first determines the location of the defect in the photomask; then, a resist layer is formed on the surface of the defect, covering the defect; next, a photoresist layer is formed, distributed around the resist layer, and the photoresist layer and the resist layer are non-adhesive; then, using the photoresist layer as a mask, the resist layer and the defect are etched to remove the resist layer and the defect. Because the photoresist layer and the resist layer are non-adhesive, no photoresist layer forms on the surface of the resist layer during the formation of the photoresist layer. Therefore, the photoresist layer forms around the resist layer. Thus, after the photoresist layer is formed, there is no need for exposure, baking, and development processes; the photoresist layer can be directly used as a mask to etch the resist layer and the defect, thereby removing the resist layer and the defect. The process of photomask repair has been simplified, avoiding the need for secondary exposure of the photomask, shortening the photomask repair cycle, and improving the repair accuracy.

[0052] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to mutually. In addition, different parts between embodiments can also be combined with each other, and this invention does not limit this.

[0053] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method of defect repair of a reticle, characterized by, The application relates to a method for repairing defects in a photomask. The method comprises the following steps: providing a photomask; determining the position of a defect in the photomask, the defect being a metal residue; forming a resist layer on the surface of the defect, the resist layer covering the defect; forming a photoresist layer on the photomask, the photoresist layer being distributed around the resist layer, and the photoresist layer and the resist layer having non-adhesion therebetween; 2. The method of claim 1, wherein etching the resist layer and the defect with the photoresist layer as a mask to remove the resist layer and the defect.

3. The method for repairing defects in a photomask as described in claim 2, characterized in that, The material of the resist layer is polydimethylsiloxane. The method for forming the resist layer comprises the following steps: forming an uncured resist material layer on the defect by a point-by-point process; 4. The method for repairing defects in a photomask as described in claim 3, characterized in that, baking the resist material layer to cure the resist material layer and form the resist layer.

5. The method of claim 1, wherein When the resist material layer is baked, the baking temperature is 90-130 DEG C, and the baking time is 10-25 min.

6. The method of claim 5, wherein the step of repairing the defect on the reticle is performed by a method selected from the group consisting of: ion implantation, laser ablation, and chemical etching. 5 The photomask comprises a light-transmitting substrate and a patterned light-blocking layer on the surface of the light-transmitting substrate, the patterned light-blocking layer exposing part of the surface of the light-transmitting substrate, and the defect being located on the exposed surface of the light-transmitting substrate.

7. The method for repairing defects in a photomask as described in claim 5, characterized in that, The top surface of the resist layer is higher than the top surface of the patterned light-blocking layer.

8. The method of claim 1, wherein The photoresist layer is formed by a spin coating process, the photoresist layer covering the patterned light-blocking layer and covering the exposed surface of the light-transmitting substrate.

9. The method of claim 1, wherein After the resist layer and the defect are etched, the method for repairing defects in the photomask further comprises performing a cleaning process to remove the remaining photoresist layer on the photomask.

10. The method of claim 1, wherein The resist layer and the defect are etched by a dry etching process to remove the resist layer and the defect. The material of the photoresist layer is phenolic resin.

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