Two-step developing method for photoetching mask

Abstract

The invention provides a two-step developing method for a photoetching mask plate. The two-step developing method comprises the following steps: S1, fixing a mask substrate subjected to laser direct writing exposure on a carrying table; s2, washing the photoresist surface on the surface of the mask substrate by using deionized water; s3, uniformly coating a layer of developing solution on the surface of the photoresist, and then keeping immersion for t1; s4, continuously washing the surface of the photoresist by using the deionized water; s5, coating a layer of developing solution on the surface of the photoresist again, and then keeping immersion for the duration of t2; s6, continuously washing the surface of the photoresist by using the deionized water; s7, carrying out high-speed rotary spin-drying on the photoresist; t1 is less than t2. The developing method can effectively reduce the photoresist wet developing residue problem, and has the advantages of good developing effect, low production cost and the like.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor photolithography, and in particular to a two-step developing method for a photolithography mask. Background Art

[0002] Reticles are the pattern transfer tools or masters used in the flat panel display and large-scale integrated circuit industries. They carry information such as graphic design and process technology, and therefore play a crucial role. With the continuous advancement of process technology in the integrated circuit industry (increasing integration density and reducing power consumption), the critical dimension (CD) of the reticle needs to be continuously reduced, gradually developing towards nodes of 180nm, 130nm, 90nm, 65nm, 28nm, and below. The manufacturing process of photolithography masks is complex, and the processing flow mainly includes CAM patterning, photoresist coating, exposure, development, etching, and inspection. After the photoresist is exposed to form a latent image, wet development to create a three-dimensional relief pattern is a key step in the photolithography process.

[0003] As chip manufacturing processes reach the 0.13μm node, the line widths of patterns on photolithography masks shrink, aspect ratios increase, and pattern density increases, leading to an increasingly serious problem of photoresist development residue. This residue not only causes wafer pattern distortion and line width deviation, but in severe cases, can lead to fatal defects such as device shorts or opens, significantly increasing production costs and R&D cycles. This poses a key challenge to mask manufacturing yield and performance. Exploring the causes of photoresist development residue and implementing systematic solutions is crucial for improving mask quality and advancing lithography technology.

[0004] The chemically amplified resist (CAR) used in deep ultraviolet direct write exposure is composed of polymer resin, photoacid generator and corresponding additives and solvents. It generally exhibits poor hydrophilicity and is prone to incomplete development during development, ultimately forming incompletely resolved opaque defects on the mask's light-shielding layer (Cr film). When the defects on the mask are transferred to the wafer, the yield can easily be reduced.

[0005] CAMark et al. proposed a dynamic analysis model for photoresist development, such as Figure 1 As shown. F1 represents the diffusion of the developer to the photoresist surface, F2 represents the reaction between the developer and the photoresist, and F3 represents the reverse diffusion of the reaction products into the developer. Assuming that F3 diffuses very quickly, it can be ignored. D Indicates the volume concentration of the developer, C S represents the developer concentration on the photoresist surface. F1 is driven by the developer concentration gradient between the liquid and the photoresist surface. F2 depends on the concentration of the two reactants on the photoresist surface (C SIncreasing the hydrophilicity of the photoresist surface is equivalent to increasing the contact area between the developer and the photoresist surface, which can accelerate the reaction between the developer and the photoresist, help increase the diffusion rate of F1, and enable the photoresist pattern to be fully developed. At the same time, it helps to improve the development resolution and form steeper photoresist pattern sidewalls.

[0006] In the existing photolithography mask development process, spray development is usually completed in one step. The mask carrier rotates at high speed and sprays a large amount of developer on the photoresist surface. Not only is a large amount of developer thrown out due to centrifugal force, resulting in waste, but also due to the large surface tension of the photoresist, incomplete development is easily caused, forming photoresist residue.

[0007] In view of this, it is necessary to propose a new photolithography mask developing method. Summary of the Invention

[0008] The purpose of the present invention is to solve the problem of residual photoresist in wet development and reduce the loss and waste of developer.

[0009] To achieve the above objectives, the present invention provides a two-step development method for a photolithography mask, and its technical solution is as follows: A two-step development method for a photolithography mask comprises the following steps: S1, fixing the mask substrate that has been subjected to laser direct writing exposure on a stage; S2. Rinse the photoresist surface on the mask substrate with deionized water; S3, uniformly coating a layer of developer on the surface of the photoresist, and then keeping it immersed for t1; S4, continue to rinse the photoresist surface with deionized water; S5, re-coating a layer of developer on the surface of the photoresist, and then keeping it immersed for t2; S6. Continue to rinse the photoresist surface with deionized water; S7, spinning the photoresist at high speed to dry; The above t1<t2.

[0010] Preferably, in step S1: During the flushing process, the carrier is controlled to rotate at a speed of 100-300 r / min, and the flushing time is 10-15 s.

[0011] Preferably, in step S2: During the coating process, the carrier is controlled to rotate at a speed of 30-50 r / min; after the coating is completed, the photoresist surface is immersed in the developer layer for 2-5 seconds.

[0012] Preferably, in step S3: During the flushing process, the carrier is controlled to rotate at a speed of 100-300 r / min, and the flushing time is 10-15 s.

[0013] Preferably, in step S4: During the coating process, the carrier is controlled to rotate at a speed of 30-50 r / min. After the coating is completed, the photoresist surface is immersed in the developer layer for 20-30 seconds.

[0014] Preferably, in step S5: During the flushing process, the carrier is controlled to rotate at a speed of 100-300 r / min, and the flushing time is 10-15 s.

[0015] Preferably, the deionized water and the developer are sprayed by different nozzles for different durations of time.

[0016] Preferably, the developer in steps S2 and S4 may be TMAH or KOH. Preferably, in step S6: During the drying process, the carrier is controlled to rotate at a speed of 1000-1500r / min, and the drying time is 20-30s.

[0017] Compared with the prior art, the technical solution of the present invention has at least one of the following beneficial effects: 1. Two-step spin immersion development is adopted. The first step is a short-time, small-volume spin immersion development, which is equivalent to pre-treating the exposed area to improve its hydrophilicity. In the second step, the spin immersion development can accelerate the reaction between the developer and the photoresist in the exposed area, which is conducive to the complete development of the photoresist pattern. 2. The two-step spin-on immersion development helps improve development resolution and form steeper photoresist pattern sidewalls; 3. The two-step spin-capping immersion development helps to improve the development uniformity; 4. The amount of developer used is small, effectively reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the Mark model of the photoresist wet development in the prior art; Figure 2 is a two-step development flow chart of a photolithography mask in an embodiment; Figure 3 is a schematic cross-sectional structure diagram of a photolithography mask in an embodiment; The specific reference numerals in the accompanying drawings are as follows: 101 - glass substrate; 102 - opaque layer; 103 - anti-reflection layer; 104 - photoresist. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are simplified and not precisely proportioned, and are merely schematic illustrations of the basic concept of the present invention. The number, form, and proportion of components in actual implementation may be more complex, and therefore should not be used to limit the scope of protection of the present invention.

[0020] In addition, in the detailed description of the following embodiments, specific details are provided to facilitate a more thorough understanding of the examples, and those skilled in the art can practice without these specific details.

[0021] During the photolithography mask manufacturing process, photoresist is exposed to laser direct writing to form a latent image. Three-dimensional relief structures can then be formed using immersion development, spray development, or spin-on immersion development. In actual production, the problem of residual photoresist after development can lead to a decrease in photolithography mask yield, especially as chip manufacturing processes improve, line widths become thinner, and aspect ratios increase. Through in-depth research into the causes of residual photoresist after development and exploration of improvements to the development process, the inventors have proposed a two-step development method for photolithography masks.

[0022] This embodiment proposes a two-step development method for a photolithography mask. Figure 2 , which shows a flow chart of the development process, the method at least includes the following steps: First, please combine Figure 3 A in the mask substrate is composed of a glass substrate, a light shielding layer, an anti-reflection layer and a photoresist. When a laser direct writing exposure machine is used to directly write and expose the photoresist layer 104 to form a latent image, please combine Figure 3 B in the figure is ready for wet development.

[0023] S1. Fixing the mask substrate that has been exposed by laser direct writing on a stage.

[0024] S2. Rinse the photoresist surface on the mask substrate with deionized water. Specifically, the exposed mask substrate is mounted on a reticle stage. While deionized water is being sprayed, the stage rotates at high speed. For example, at a rotation speed of 300 rpm, the deionized water rinses the photoresist surface and is then ejected by centrifugal force, carrying away surface particles. This step can last for 10 seconds.

[0025] Deionized water spray rinsing can wet the photoresist and reduce its surface tension, which is conducive to the next step of evenly spreading the developer on the photoresist surface.

[0026] S3, uniformly coating a layer of developer on the surface of the photoresist, and then keeping it immersed for t1 time.

[0027] In this step, specifically, the stage speed is set to 30r / min. While the mask substrate rotates slowly, the developer is sprayed on the surface of the photoresist and quickly covers the photoresist due to the centrifugal force. The rotation time is set to 3s to ensure that a layer of developer liquid with a thickness of about 2-3mm is formed on the surface of the photoresist, and then the stage stops rotating. The surface of the photoresist is immersed in the developer layer for 3s (i.e., t1). After this step is completed, the exposed area of ​​the photoresist is preliminarily developed to form a three-dimensional structure of a certain depth, but it is not developed to the bottom. At this time, the critical dimension (CD) of the lithography is defined. Importantly, please combine Figure 3 In the example C, the bottom of the exposed area of ​​the photoresist shows a large roughness after the initial development, which will show better hydrophilicity in the subsequent second spin-on immersion development process, increasing the reaction area between the photoresist and the developer, which is beneficial to improving the wet development rate.

[0028] S4. Continue to rinse the photoresist surface with deionized water.

[0029] In this step, deionized water is sprayed onto the photoresist surface while the stage rotates at 300 rpm to remove any residual developer and development products from the photoresist surface. This step is set to 10 seconds to ensure that the first developer application is completely rinsed. Importantly, the initially developed photoresist grooves should be free of residual developer so that the photoresist to be developed can be exposed to fresh developer during the subsequent second developer application.

[0030] S5. Re-coat a layer of developer on the surface of the photoresist, and then keep it immersed for t2 time.

[0031] In this step, specifically, the stage rotation speed is set to 30r / min. While the mask substrate is rotating slowly, the developer is sprayed onto the photoresist surface and quickly covers the photoresist due to the centrifugal force. The duration of the coating process is set to 10s to ensure that a layer of developer with a thickness of about 5mm is formed on the photoresist surface. Then the stage rotation is stopped. The photoresist surface is immersed in the developer layer for 30s (i.e., t2). Please combine Figure 3 At step D, the exposed areas of the photoresist are fully developed, revealing the anti-reflection layer 103 underneath. The critical dimensions, depth, profile, and straightness of the lithography are finally defined. Importantly, the amount of developer applied in this step should be greater than that applied the first time.

[0032] S6. Continue to rinse the photoresist surface with deionized water.

[0033] In this step, deionized water is sprayed onto the photoresist surface while the stage rotates at 300 rpm to remove any residual developer and developer products. This step is set to 15 seconds to ensure that no residual developer remains on the photoresist surface or in the pattern grooves.

[0034] S7. Spin the photoresist at high speed to dry it.

[0035] In this step, specifically, the stage speed is set to 1500 rpm and the spin-drying time is set to 30 seconds. At this point, the photolithography mask development is completed.

[0036] In summary, the two-step photolithography mask development method of the above embodiment is applicable to DNQ type i-line resin and CAR type DUV photoresist, can develop binary mask (BIM) and phase shift mask (PSM), etc., can effectively reduce the residual phenomenon of wet development of photoresist, and has the advantages of good development effect and low production cost.

[0037] Of course, in the photolithography mask manufacturing process, from core steps such as coating, exposure, and development, to strict post-processing, environmental control, and continuous process monitoring, each step is closely related and works together to reduce the risk of residual photoresist after development.

[0038] It should be pointed out that the above embodiments are only for illustrating the technical ideas and features of the present invention and cannot limit the scope of protection of the present invention. Any equivalent substitutions or changes made based on the essential content of the present invention are within the scope of protection of the present invention.

Claims

1. A two-step development method for a photolithography mask, characterized in that: The following steps are involved: S1, fixing the mask substrate that has been subjected to laser direct writing exposure on a stage; S2. Rinse the photoresist surface on the mask substrate with deionized water; S3, uniformly coating a layer of developer on the surface of the photoresist, and then keeping it immersed for t1; S4, continue to rinse the photoresist surface with deionized water; S5, re-coating a layer of developer on the surface of the photoresist, and then keeping it immersed for t2; S6. Continue to rinse the photoresist surface with deionized water; S7, spinning the photoresist at high speed to dry; The above t1<t2.

2. A two-step development method for a photolithography mask according to claim 1, characterized in that: In step S1: During the flushing process, the carrier is controlled to rotate at a speed of 100-300 r / min, and the flushing time is 10-15 s.

3. The two-step development method for a photolithography mask according to claim 1, characterized in that: In step S2: During the coating process, the carrier is controlled to rotate at a speed of 30-50 r / min; after the coating is completed, the photoresist surface is immersed in the developer layer for 2-5 seconds.

4. The two-step development method for a photolithography mask according to claim 1, wherein: In step S3: During the flushing process, the carrier is controlled to rotate at a speed of 100-300 r / min, and the flushing time is 10-15 s.

5. The two-step development method for a photolithography mask according to claim 1, wherein: In step S4: During the coating process, the carrier is controlled to rotate at a speed of 30-50 r / min. After the coating is completed, the photoresist surface is immersed in the developer layer for 20-30 seconds.

6. The two-step development method for a photolithography mask according to claim 1, characterized in that: In step S5: During the flushing process, the carrier is controlled to rotate at a speed of 100-300 r / min, and the flushing time is 10-15 s.

7. A two-step development method for a photolithography mask according to any one of claim 1, characterized in that: The deionized water and the developer are sprayed by different nozzles for different durations of time.

8. The two-step development method for a photolithography mask according to claim 1, wherein: The developer in steps S2 and S4 may be TMAH or KOH.

9. The two-step development method for a photolithography mask according to claim 1, characterized in that: In step S6: During the drying process, the carrier is controlled to rotate at a speed of 1000-1500r / min, and the drying time is 20-30s.

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