Edge photoresist removing method for negative photoresist photoetching process

Abstract

The invention relates to an edge photoresist removing method for a negative photoresist photoetching process, which comprises the following steps of: (1) spin-coating negative photoresist on a substrate, and stacking the edge of the substrate to form edge photoresist higher than a middle area; carrying out first soft baking on the substrate; (2) spin-coating positive photoresist, and carrying out secondary soft baking on the substrate; (3) exposing the substrate by using an edge-removing mask plate and edge-removing ultraviolet light; (4) developing the substrate by using a developing solution, and removing edge glue; (5) exposing the substrate by using a patterned mask plate and patterned ultraviolet light, and performing post-baking after exposure; (6) exposing the substrate by using the universal exposure ultraviolet light; and (7) developing the substrate by using a developing solution, and removing all the positive photoresist and the negative photoresist corresponding to the shading region of the patterned mask plate in the step (5) to obtain the patterned photoresist. The method for removing the negative glue and the edge glue is simple to operate, does not need additional process equipment, is high in compatibility of a photoetching process, and is accurate and controllable in an edge removal area.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor process, and particularly relates to an edge resist removal method for negative resist photolithography process. Background Art

[0002] When spin coating photoresist, especially for thick photoresist, a thick layer of photoresist, the so-called edge glue, will accumulate on the edge of the substrate. The edge glue makes the edge of the substrate bulge abnormally. The problems in contact exposure are: since the edge glue is thick, it is not easy to fully dry it in soft baking, and the edge glue is easy to adhere to the mask plate and contaminate the mask plate; the raised edge glue causes unnecessary gaps between the substrate and the mask plate, resulting in poor resolution of the photolithography pattern and large dimensional errors.

[0003] There are two commonly used methods for removing edge glue. One is the chemical method. After soft baking, a small amount of edge glue removal solvent is sprayed to the edge of the substrate with an edge remover to dissolve the edge glue and rotate to shake off the solution; or a cotton swab is directly dipped in a small amount of edge glue removal solvent and carefully wiped the edge glue. The edge removal area and size of this method are not easy to control accurately, and it is easy to damage the effective area of ​​the photoresist, and the rotating edge remover can only remove the edge glue in the annular area. The other is the optical method. The edge of the substrate is exposed by laser, the photoresist is decomposed, and the edge glue is dissolved by the developer to achieve the purpose of removal, or the effective area of ​​the photoresist is blocked by a mask plate, and the photolithography machine is used for exposure and then development to remove the edge glue. The area and size of the edge glue removal by the optical method can be precisely controlled, and the shape of the edge glue removal area is not limited. However, the optical method is only effective for positive photoresist edge removal. For negative photoresist, it can be dissolved in the developer when it is not exposed, but if the edge is exposed, it cannot be dissolved in the developer. Therefore, the conventional optical edge glue removal method cannot be used for negative photoresist process. In addition, negative photoresist often has high viscosity and thick photoresist, and the edge glue accumulation problem is more prominent, which seriously affects the accuracy of photolithography graphics. Therefore, it is urgent to solve the problem of edge resist accumulation in negative resist lithography process and to precisely control the edge resist removal area. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for removing edge glue for negative photolithography process, so as to achieve the purpose of removing edge glue and improving the accuracy of photolithography pattern without changing the final photoresist pattern.

[0005] Based on the characteristics of positive and negative photoresists, the present invention provides a method for removing edge resists in a negative resist photolithography process, comprising the following steps:

[0006] (1) Spin coating negative photoresist: Spin coating negative photoresist on the substrate, and the edge of the substrate is accumulated to form an edge resist higher than the middle area; the substrate is soft-baked for the first time;

[0007] (2) Spin coating protective glue: Spin coating positive photoresist and soft baking the substrate for the second time;

[0008] (3) Edge removal exposure: Expose the substrate using an edge removal mask and edge removal ultraviolet light;

[0009] (4) Edge removal and development: Use developer to develop the substrate and remove the edge glue;

[0010] (5) Patterned exposure and post-baking: The substrate is exposed using a patterned mask and patterned ultraviolet light, and then post-baked;

[0011] (6) Flood exposure: Expose the substrate with flood UV light;

[0012] (7) Patterned development: Developing the substrate with a developer to remove all positive photoresists and the negative photoresists corresponding to the light-shielding areas of the patterned mask in step (5) to obtain patterned photoresists.

[0013] Preferably, the first soft baking temperature in step (1) is 80-150° C. and the time is 1-30 min.

[0014] Preferably, the second soft baking temperature in step (2) is 80-150° C. and the time is 1-10 min.

[0015] Preferably, in the step (3), the light-shielding area of ​​the edge removal mask corresponds to the effective area of ​​the substrate photoresist, and the light-transmitting area corresponds to the edge glue area.

[0016] More preferably, in step (3), the edge removal mask plate determines the shape of the edge glue removal area.

[0017] Preferably, the edge removal and development accuracy in step (4) does not exceed 10 um.

[0018] Preferably, in step (5), the post-baking temperature is 80-150° C. and the time is 1-10 min.

[0019] For positive photoresist, it is originally insoluble in developer, but after being exposed to ultraviolet light, a photochemical reaction occurs and it becomes soluble in developer. For negative photoresist, it is originally soluble in developer, but after being exposed to ultraviolet light and heated, the photoresist is cross-linked and cured, making it insoluble in developer. If it is only exposed to ultraviolet light without heating and baking, the photoresist cannot be cross-linked and cured, and it is still soluble in developer.

[0020] Beneficial Effects

[0021] The edge removal method of the present invention is simple to operate, does not require additional process equipment, has high compatibility with photolithography processes, and the edge removal area is precisely controllable, which effectively solves the problem that negative photolithography processes cannot perform precise optical edge removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a schematic diagram of the overall process of the edge glue removal method of the present invention.

[0023] Figure numerals: 1-substrate, 2-negative photoresist, 3-edge glue, 4-positive photoresist, 5-edge removal mask, 6-edge removal ultraviolet light, 7-patterning mask, 8-patterning ultraviolet light, 9-flood exposure ultraviolet light, 10-patterning photoresist. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0025] The edge stripping method for negative photolithography of the present invention comprises the following steps:

[0026] (1) Spin coating negative photoresist: First, spin coat negative photoresist 2 on substrate 1, and the edge of substrate 1 is accumulated to form edge glue 3 higher than the middle area; perform the first soft baking on substrate 1 to fully dry the solvent to prevent the two glues from dissolving each other when spin coating the second layer of photoresist;

[0027] (2) Spin-coating protective glue: Spin-coating protective positive photoresist 4, and performing a second soft bake on the substrate 1; the purpose of spin-coating the positive photoresist 4 is to protect the negative photoresist 2 in the effective area from being dissolved during edge removal and development;

[0028] (3) Edge removal exposure: The substrate 1 is exposed using the edge removal mask 5 and the edge removal ultraviolet light 6. The light-shielding area of ​​the edge removal mask 5 corresponds to the effective area of ​​the photoresist of the substrate 1, and the light-transmitting area corresponds to the edge glue 3 area, that is, the edge removal ultraviolet light 6 is only exposed in the edge glue 3 area.

[0029] (4) Edge removal development: The substrate 1 is developed with a developer. The positive photoresist 4 in the exposed area is soluble in the developer. Since there is no post-baking, the negative photoresist 2 is soluble in the developer regardless of whether it is exposed or not. However, the negative photoresist 2 in the unexposed area is protected by the positive photoresist 4. Therefore, only the negative photoresist 2 and the positive photoresist 4 with exposed edges can be dissolved, thus achieving the purpose of removing the edge glue 3. In addition, the shape of the area where the edge glue 3 is removed is completely determined by the edge removal mask plate 5, which can be arbitrarily designed as needed, and the edge removal development accuracy is high, not exceeding 10um.

[0030] (5) Patterned exposure and post-baking: The substrate 1 is exposed using a patterned mask 7 and patterned ultraviolet light 8, and then post-baked. After the post-baking, the exposed area of ​​the negative photoresist 2 is insoluble in the developer;

[0031] (6) Flood exposure: No mask is required, and the substrate 1 is exposed with flood exposure ultraviolet light 9. The positive photoresist 4 is completely exposed and can be dissolved in the developer.

[0032] (7) Patterned development: The substrate 1 is developed with a developer to dissolve all the positive photoresist 4 and the negative photoresist 2 corresponding to the light-shielding area of ​​the patterned mask 7 in step (5), thereby obtaining a patterned photoresist 10.

[0033] Example

[0034] The edge stripping method for negative photolithography in this embodiment has the following overall process: Figure 1 As shown, the specific steps are as follows:

[0035] (1) Spin coating negative photoresist: First, spin coat AZ2070 negative photoresist on the substrate at a speed of 3000 rpm for 30 seconds. Perform the first soft bake on the substrate and fully dry it at a temperature of 100°C for 10 minutes. The thickness of AZ2070 negative photoresist is about 5 μm, and thicker edge glue is obviously accumulated at the edge of the substrate.

[0036] (2) Spin coating protective glue: Spin coating protective AZ1500 positive photoresist on the substrate at a speed of 3000 rpm for 30 seconds. Perform a second soft bake on the substrate at a temperature of 100°C for 3 minutes. AZ1500 positive photoresist is thin, with a thickness of about 1.5um.

[0037] (3) Edge removal exposure: The substrate is exposed using a SUSS MA8 UV exposure machine and an edge removal mask for 30 seconds. The light-transmitting area of ​​the designed edge removal mask corresponds to the edge glue area on the substrate, so the UV light is only exposed to the edge glue area. The edge removal exposure does not need to be too long, and only the AZ1500 positive photoresist needs to be exposed.

[0038] (4) Edge removal and development: The substrate is developed with AZ300 MIF developer for 5 minutes. The exposed edges of the AZ2070 negative photoresist and AZ1500 positive photoresist are dissolved, that is, the edge glue is completely dissolved.

[0039] (5) Patterned exposure and post-baking: The substrate was exposed using a SUSS MA8 UV exposure machine and a patterned mask for 6 seconds. After exposure, post-baking was performed at 110°C for 90 seconds. After post-baking, the exposed area of ​​AZ2070 negative photoresist was insoluble in the developer.

[0040] (6) Flood exposure: No mask is required. The substrate is flood exposed using a SUSS MA8 UV exposure machine for 20 seconds. The AZ1500 positive photoresist is fully exposed and can be dissolved in the developer.

[0041] (7) Patterning development: The substrate is developed with AZ300 MIF developer for 2 min 30 s to dissolve all of the AZ1500 positive photoresist and the AZ2070 negative photoresist corresponding to the light-shielding area of ​​the patterned mask in step (5) to obtain a patterned photoresist.

[0042] The patterned photoresist obtained by the method of the present invention has the same pattern as the patterned photoresist obtained by photolithography without edge removal, but has higher precision and more accurate size.

Claims

1. A method for edge stripping in a negative photoresist lithography process, comprising the following steps: (1) Spin coating negative photoresist: spin coating negative photoresist (2) on a substrate (1), with the edge of the substrate (1) being accumulated to form an edge glue (3) higher than the middle area; performing a first soft bake on the substrate (1); (2) Spin coating protective glue: spin coating positive photoresist (4), and performing a second soft bake on the substrate (1); (3) edge removal exposure: exposing the substrate (1) using an edge removal mask (5) and edge removal ultraviolet light (6); (4) edge removal and development: developing the substrate (1) with a developer to remove the edge glue (3); (5) Patterned exposure and post-baking: exposing the substrate (1) using a patterned mask (7) and patterned ultraviolet light (8), and post-baking after exposure; (6) flood exposure: exposing the substrate (1) with flood exposure ultraviolet light (9); (7) Patterned development: developing the substrate (1) with a developer to remove all the positive photoresist (4) and the negative photoresist (2) corresponding to the light-shielding area of ​​the patterned mask (7) in step (5), thereby obtaining a patterned photoresist (10).

2. The edge stripping method for negative photolithography according to claim 1, characterized in that: The first soft baking temperature in step (1) is 80-150° C. and the time is 1-30 min.

3. The edge stripping method for negative resist photolithography according to claim 1, characterized in that: The second soft baking in step (2) is performed at a temperature of 80 to 150° C. for 1 to 10 minutes.

4. The edge stripping method for negative photolithography according to claim 1, characterized in that: In the step (3), the light-shielding area of ​​the edge removal mask plate (5) corresponds to the effective area of ​​the photoresist of the substrate (1), and the light-transmitting area corresponds to the edge glue (3) area.

5. The edge stripping method for negative resist photolithography process according to claim 1, characterized in that: In the step (3), the edge removal mask plate (5) determines the shape of the area where the edge glue (3) is to be removed.

6. The edge stripping method for negative resist photolithography process according to claim 1, characterized in that: The edge removal and development accuracy in the step (4) does not exceed 10 um.

7. The edge stripping method for negative resist photolithography according to claim 1, characterized in that: In the step (5), the post-baking temperature is 80 to 150° C. and the time is 1 to 10 minutes.

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