Coating method of polyimide resin

Abstract

A coating method of polyimide resin includes the steps of: S1, providing a semiconductor substrate, which refers to a wafer before a photoetch process is completed in a semiconductor process; S2, dropping a polyimide resin solution to a center position of the static semiconductor substrate; S3, rotating the semiconductor substrate at a first speed for a first time after the polyimide resin solution is dropped; S4, rotating the semiconductor substrate at a second speed for a second time immediately after the first time of step S3 ends, the second speed is greater than the first speed; S5, rotating the semiconductor substrate at a third speed for a third time immediately after the second time of step S4 ends, the third speed is controlled to be greater than the second speed; S6, rotating the semiconductor substrate at a fourth speed for a fourth time immediately after the third time of step S5 ends, the fourth speed is greater than the third speed. Thus, the thickness of the polyimide resin solution spread on the whole semiconductor substrate is uniform, thereby improving the performance and yield of products.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of semiconductor production and manufacturing, and more particularly to a coating method of polyimide resin. BACKGROUND

[0002] Photoresist coating is completed in the coating unit of the spin coater, which is responsible for photoresist coating on the wafer surface to achieve the specified thickness and uniformity. Photoresist coating is mainly divided into two stages. The first step is to pre-wet the bottom of the wafer to make the photoresist spin coating more uniform. The second step is photoresist spin coating. The rotation speed is 1650 rpm when spraying photoresist. When the photoresist is evenly distributed on the entire wafer, it enters the high-speed rotation stage, which is to make the photoresist evenly distributed on the entire wafer by centrifugal force, and to spin off the excess photoresist.

[0003] The existing coating technology can make the film thickness and uniformity of the photoresist meet the requirements of the process, but when polyimide is coated on the surface in this way, the uniformity of the coating is poor due to the high viscosity of the polyimide. SUMMARY

[0004] In view of the problems in the background art, the purpose of the present disclosure is to provide a coating method of polyimide resin, which can make the thickness of the polyimide resin solution evenly distributed on the entire semiconductor substrate uniform.

[0005] Therefore, a coating method of polyimide resin includes the following steps: S1, providing a semiconductor substrate, which refers to a wafer in the process before the photolithography process in the semiconductor process; S2, dropping polyimide resin solution at the center position of the stationary semiconductor substrate; S3, rotating the semiconductor substrate at a first speed for a first time after the polyimide resin solution is dropped; S4, immediately rotating the semiconductor substrate at a second speed for a second time after the first time of step S3 ends, the second speed being greater than the first speed; S5, immediately rotating the semiconductor substrate at a third speed for a third time after the second time of step S4 ends, the third speed being controlled to be greater than the second speed; S6, immediately rotating the semiconductor substrate at a fourth speed for a fourth time after the third time of step S5 ends, the fourth speed being greater than the third speed.

[0006] The beneficial effects of the present disclosure are as follows: in the coating method of polyimide resin according to the present disclosure, the required amount of polyimide resin solution for coating thickness is dropped at the center position of the stationary semiconductor substrate by step S2, and the semiconductor substrate is rotated at four speeds from full to fast by steps S3 to S6, so that the thickness of the polyimide resin solution evenly distributed on the entire semiconductor substrate is uniform, thereby improving the performance and yield of the product. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a test chart of uniformity after coating of the polyimide resin solution of Example 1 is completed.

[0008] Figure 2 is a test chart of uniformity after coating of the polyimide resin solution of Comparative Example 1 is completed.

[0009] Figure 3 is a test chart of uniformity after coating of the polyimide resin solution of Comparative Example 2 is completed.

[0010] Figure 4 is a test chart of uniformity after coating of the polyimide resin solution of Comparative Example 3 is completed. DETAILED DESCRIPTION

[0011] The accompanying drawings illustrate embodiments of the present disclosure and, it is to be understood that the disclosed embodiments are merely representative of the present disclosure, the present disclosure can be embodied in various forms, therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to variously embody the present disclosure.

[0012] [Coating method of polyimide resin]

[0013] The coating method of polyimide resin according to the present disclosure comprises the steps of:

[0014] S1, providing a semiconductor substrate, which refers to a wafer in the process before the photolithography process is completed in the semiconductor process;

[0015] S2, dropping polyimide resin solution to the center position of the stationary semiconductor substrate;

[0016] S3, after the polyimide resin solution is dropped, rotating the semiconductor substrate at a first speed for a first time;

[0017] S4, immediately after the first time of step S3 is completed, rotating the semiconductor substrate at a second speed for a second time, the second speed is greater than the first speed;

[0018] S5, immediately after the second time of step S4 is completed, rotating the semiconductor substrate at a third speed for a third time, the third speed is controlled to be greater than the second speed;

[0019] S6, immediately after the third time of step S5 is completed, rotating the semiconductor substrate at a fourth speed for a fourth time, the fourth speed is greater than the third speed.

[0020] In the coating method of the polyimide resin according to the present disclosure, the dropping of the amount of the polyimide resin solution required for the coating thickness at the center position of the stationary semiconductor substrate is completed by the step S2, and the rotation of the semiconductor substrate at four rates from full to fast by the steps S3 to S6 causes the thickness of the polyimide resin solution spread on the entire semiconductor substrate to be uniform, thereby improving the performance and yield of the product.

[0021] In an example, in the step S3, the rotation of the semiconductor substrate at the first rate for the first time causes the imide resin solution to spread to a position from the center of the semiconductor substrate to less than half of the radius of the semiconductor substrate; in the step S4, the rotation of the semiconductor substrate at the second rate for the second time immediately after the end of the first time of the step S3 causes the imide resin solution to spread to a position from the center of the semiconductor substrate to equal to half of the radius of the semiconductor substrate; in the step S5, the rotation of the semiconductor substrate at the third rate for the third time immediately after the end of the second time of the step S4 causes the imide resin solution to spread to a position from the center of the semiconductor substrate to more than half of the radius of the semiconductor substrate but less than the radius of the semiconductor substrate; and in the step S6, the rotation of the semiconductor substrate at the fourth rate for the fourth time immediately after the end of the third time of the step S5 causes the imide resin solution to spread to a position from the center of the semiconductor substrate to equal to the radius of the semiconductor substrate.

[0022] In an example, the viscosity of the polyimide resin solution is not less than 2000 cp. Further, the viscosity of the polyimide resin solution is 3000 cp.

[0023] In an example, the solvent of the polyimide resin solution is 1-methyl-2-pyrrolidone accounting for 85-90% of the total polyimide resin solution in mass.

[0024] In an example, the semiconductor substrate sequentially comprises a silicon substrate, a lower protective layer, a dielectric layer, and an upper protective layer from bottom to top. The lower protective layer and the upper protective layer can be, but are not limited to, a silicon nitride layer. The dielectric layer can be, but is not limited to, titanium.

[0025] In an example, in the step S3, the first rate is controlled at 100±10 rpm, and the time is 2±0.3 s.

[0026] In an example, in the step S4, the second rate is controlled at 400±20 rpm, and the time is 1.5±0.2 s.

[0027] In an example, in the step S5, the third rate is controlled at 650±30 rpm, and the time is 1.5±0.2 s.

[0028] In an example, in the step S6, the fourth rate is controlled at the time is 1±0.1 s.

[0029] [TEST]

[0030] Example 1

[0031] Example 1 adopts the following steps:

[0032] S1, providing a semiconductor substrate, which refers to a wafer before the photolithography process in the semiconductor process, the semiconductor substrate is silicon substrate from bottom to top, a silicon nitride layer of 1000A, a titanium layer of 1000A, a silicon nitride layer of 1000A;

[0033] S2, dropping polyimide resin solution to the center position of the static semiconductor substrate, the solvent of the polyimide resin solution is 1-methyl-2-pyrrolidone with a mass of 90% of the total polyimide resin solution, and the viscosity of the polyimide resin solution is 3000cp;

[0034] S3, after the polyimide resin solution is dropped, rotating the semiconductor substrate at a first speed for a first time, the first speed is controlled at 100rpm, and the first time is 2s;

[0035] S4, immediately after the first time of step S3 ends, rotating the semiconductor substrate at a second speed for a second time, the second speed is controlled at 400rpm, and the second time is 1.5s;

[0036] S5, immediately after the second time of step S4 ends, rotating the semiconductor substrate at a third speed for a third time, the third speed is controlled at 650rpm, and the third time is 1.5s;

[0037] S6, immediately after the third time of step S5 ends, rotating the semiconductor substrate at a fourth speed for a fourth time, the fourth speed is controlled at 800rpm, and the fourth time is 1s.

[0038] That is, example 1 adopts four-step coating mode of four speeds from full to fast.

[0039] Comparative Example 1

[0040] Comparative Example 1 adopts the following steps:

[0041] S1, providing a semiconductor substrate, which refers to a wafer before the photolithography process in the semiconductor process, the semiconductor substrate is silicon substrate from bottom to top, a silicon nitride layer of 1000A, a titanium layer of 1000A, a silicon nitride layer of 1000A;

[0042] S2, dropping polyimide resin solution to the center of the stationary semiconductor substrate, the solvent of the polyimide resin solution is 1-methyl-2-pyrrolidone which accounts for 90% of the total polyimide resin solution by mass, and the viscosity of the polyimide resin solution is 3000 cp;

[0043] S3, rotating the semiconductor substrate at a first rate for a first time after the polyimide resin solution is dropped, the first rate is controlled at 150 rpm, and the first time is 1.5 s;

[0044] That is, the comparative example 1 adopts the ordinary single rate one-step coating method.

[0045] Comparative example 2

[0046] The comparative example 2 adopts the following steps:

[0047] S1, providing a semiconductor substrate, which refers to a wafer before the photolithography process in the semiconductor process, and the semiconductor substrate is sequentially composed of a silicon substrate, a silicon nitride layer, a titanium layer, a silicon nitride layer;

[0048] S2, dropping polyimide resin solution to the center of the stationary semiconductor substrate, the solvent of the polyimide resin solution is 1-methyl-2-pyrrolidone which accounts for 90% of the total polyimide resin solution by mass, and the viscosity of the polyimide resin solution is 3000 cp;

[0049] S3, rotating the semiconductor substrate at a first rate for a first time after the polyimide resin solution is dropped, the first rate is controlled at 150 rpm, and the first time is 1.5 s;

[0050] S4, rotating the semiconductor substrate at a second rate for a second time immediately after the first time of step S3 ends, the second rate is controlled at 400 rpm, and the second time is 2 s;

[0051] S5, rotating the semiconductor substrate at a third rate for a third time immediately after the second time of step S4 ends, the third rate is controlled at 600 rpm, and the third time is 2.5 s.

[0052] That is, the comparative example 2 adopts the three-step coating method of three rates from full to fast.

[0053] Comparative example 3

[0054] Except that the fourth rate in step S6 is controlled at 830 rpm, the rest is the same as example 1.

[0055] Figures 1 to 4 The uniformity test figures after the polyimide resin solution coating of example 1 and comparative examples 1-3 respectively. The test is measured in KLA F5X film thickness meter,Figures 1 to 4 The maximum value, the average value and the minimum value of the thickness of the polyimide resin solution after the coating was finished were marked from top to bottom, and the unit was nm.

[0056] In the Figure 1 , Example 1 adopted the four-step coating method of four rates from full to fast, and the difference between the maximum value and the minimum value of the thickness of the polyimide resin solution was 43 nm.

[0057] In the Figure 2 , Comparative Example 1 adopted the ordinary one-step coating method of a single rate, and the difference between the maximum value and the minimum value of the thickness of the polyimide resin solution was 132 nm. Compared with Example 1, the uniformity of the thickness of the polyimide resin solution of Comparative Example 1 was poor. In addition, it was found from Figure 2 that the polyimide resin solution was missing in the center of the semiconductor substrate.

[0058] In the Figure 3 , Comparative Example 2 adopted the three-step coating method of three rates from full to fast, and the difference between the maximum value and the minimum value of the thickness of the polyimide resin solution was 70 nm. Compared with Comparative Example 1, the uniformity of the thickness of the polyimide resin solution was improved by adopting the three-step coating method in Comparative Example 2, but there was still a big gap compared with Example 1.

[0059] In the Figure 4 , Comparative Example 3 made the fourth rate 830 rpm exceed 820 rpm, and the difference between the maximum value and the minimum value of the thickness of the polyimide resin solution was 53 nm. Compared with Example 1 and Figure 1 , the uniformity of the thickness of the polyimide resin solution was poor. In addition, it was found from Figure 4 that the polyimide resin solution was concave in the middle of the semiconductor substrate.

Claims

1. A coating method of a polyimide resin, characterized by, The method comprises the steps of: S1, providing a semiconductor substrate, which is a wafer before a photoetching process is completed in a semiconductor process; S2, dropping a polyimide resin solution to a center position of the stationary semiconductor substrate; S3, rotating the semiconductor substrate at a first speed for a first time after the polyimide resin solution is dropped; S4, rotating the semiconductor substrate at a second speed for a second time immediately after the first time in step S3 ends, the second speed being greater than the first speed; S5, rotating the semiconductor substrate at a third speed for a third time immediately after the second time in step S4 ends, the third speed being greater than the second speed; S6, rotating the semiconductor substrate at a fourth speed for a fourth time immediately after the third time in step S5 ends, the fourth speed being greater than the third speed; In step S3, the first speed is controlled at 100±10 rpm and the first time is 2±0.3 s, so that the polyimide resin solution spreads to a position from the center of the semiconductor substrate to a position less than half of the radius of the semiconductor substrate. In step S4, the second speed is controlled at 400±20 rpm and the second time is 1.5±0.2 s, so that the polyimide resin solution spreads to a position from the center of the semiconductor substrate to a position equal to half of the radius of the semiconductor substrate. In step S5, the third speed is controlled at 650±30 rpm and the third time is 1.5±0.2 s, so that the polyimide resin solution spreads to a position from the center of the semiconductor substrate to a position greater than half of the radius of the semiconductor substrate but less than the radius of the semiconductor substrate. In step S6, the fourth speed is controlled at 800±40 rpm and the fourth time is 1.5±0.2 s, so that the polyimide resin solution spreads to a position from the center of the semiconductor substrate to a position equal to the radius of the semiconductor substrate.

2. The polyimide resin coating method according to claim 1, wherein the viscosity of the polyimide resin solution is not less than 2000 cp.

3. The polyimide resin coating method according to claim 2, wherein the viscosity of the polyimide resin solution is 3000 cp.

4. The polyimide resin coating method according to claim 1, wherein the solvent of the polyimide resin solution is 1-methyl-2-pyrrolidone, which accounts for 85-90% of the total polyimide resin solution.

5. The polyimide resin coating method according to claim 1, wherein in step S3, the first speed is controlled at 100±10 rpm and the first time is 2±0.3 s.

6. The polyimide resin coating method according to claim 5, wherein in step S4, the second speed is controlled at 400±20 rpm and the second time is 1.5±0.2 s.

7. The polyimide resin coating method according to claim 6, wherein in step S5, the third speed is controlled at 650±30 rpm and the third time is 1.5±0.2 s.

8. The polyimide resin coating method according to claim 7, wherein in step S6, the fourth speed is controlled at 800±40 rpm and the fourth time is 1.5±0.2 s. ​ ​ ​ ​ ​ ​ In step S6, the fourth rate control is performed at Time is 1 ± 0.1 s.

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