CN114350366A

CN114350366A - Silicon nitride and P-type polycrystalline silicon constant-speed etching solution

Info

Publication number: CN114350366A
Application number: CN202111503313.5A
Authority: CN
Inventors: 冯凯; 贺兆波; 崔会东; 王书萍; 张庭; 尹印; 万杨阳; 钟昌东; 李鑫; 李金航
Original assignee: Hubei Sinophorus Electronic Materials Co ltd
Current assignee: Hubei Sinophorus Electronic Materials Co ltd
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2022-04-15
Anticipated expiration: 2041-12-09
Also published as: CN114350366B

Abstract

The invention discloses a constant-speed etching solution for silicon nitride and P-type polycrystalline silicon, which mainly comprises phosphoric acid, a mononitro compound, a nitro stabilizer, a surfactant and water, and can realize that the etching rate ratio of a silicon nitride layer to a P-type polycrystalline silicon layer is stabilized at 1.0 +/-0.1 by controlling the process temperature and adjusting the addition amount of each component.

Description

Silicon nitride and P-type polycrystalline silicon constant-speed etching solution

Technical Field

The invention belongs to the field of electronic chemicals, and particularly relates to a constant-speed etching solution for silicon nitride and P-type polycrystalline silicon and a preparation method thereof

Background

In the integrated circuit manufacturing process, when a specific grid MOSFET device is prepared, two hard masks of silicon nitride and silicon dioxide need to be respectively deposited on P-type polycrystalline silicon, and after a through hole is etched by a dry method, the P-type polycrystalline silicon and the upper layer of silicon nitride hard mask need to be synchronously etched inwards for a certain depth.

The commonly used silicon nitride etching solution is high-temperature phosphoric acid, the etching rate of the high-temperature phosphoric acid to silicon nitride is about 65A/min, and the etching rate to P-type polycrystalline silicon is less than 1A/min; the etching rate of the general etching solution for the polysilicon to the polysilicon is 1000A/s, the etching selection ratio to the silicon nitride is more than 100:1, and the etching depth of the etched silicon nitride and the etched P-type polysilicon is difficult to control by adopting the etching solution to etch step by step.

Disclosure of Invention

The invention provides a constant-speed etching solution for silicon nitride and P-type polycrystalline silicon, which solves the problems that the etching appearance is difficult to control and the etching end point is difficult to judge when the silicon nitride and the P-type polycrystalline silicon layer are etched step by step.

In order to achieve the purpose, the invention adopts the technical scheme that:

the constant-speed etching solution for silicon nitride and P-type polycrystalline silicon is characterized in that the etching solution is an electronic-grade product, and the main components of the etching solution comprise phosphoric acid accounting for 75-88% of the etching solution by mass, 0.01-0.5% of mononitro compound, 0.1-1% of nitro stabilizer, 0.01-0.5% of surfactant and the balance of water.

In the scheme, the phosphoric acid is electronic grade phosphoric acid, the nitrate content is less than 0.05ppm, and the metal ion content is less than 10 ppb.

In the scheme, the boiling point of the mononitro compound is more than 160 ℃.

In the scheme, the mononitro compound is one or a mixture of more of 3-nitropyridine, 2-nitroimidazole, 3-nitrobutanol and 3-nitropropanol.

In the above scheme, the nitro stabilizer is one or a mixture of several of N-methylaniline, aniline, N-dimethylaniline and N, N '-dimethyl-N, N' -diphenylurea.

In the above scheme, the surfactant is a perfluoroalkyl carboxylic acid selected from at least one of perfluorooctanoic acid, perfluoropentanoic acid, perfluoroheptanoic acid, perfluorobutanoic acid, perfluorononanoic acid, perfluorodecanoic acid, and perfluoroundecanoic acid.

In the scheme, the etching rate ratio of the etching liquid to etch the silicon nitride and the P-type polysilicon is stabilized at 1.0 +/-0.1.

The invention has the advantages of

1. The phosphoric acid in the constant-speed etching solution of the silicon nitride and the P-type polycrystalline silicon is electronic-grade phosphoric acid with nitrate content less than 0.05ppm and metal ion content less than 10ppb, so that the etching rate of the etching solution on the P-type polycrystalline silicon cannot be influenced by the nitrate content and the metal ion content in the phosphoric acid, and the component regulation and control of the etching solution are facilitated.

2. The mononitro compound in the constant-speed etching solution of the silicon nitride and the P-type polycrystalline silicon can improve the etching rate of the etching solution on the P-type polycrystalline silicon without influencing the etching rate of the etching solution on the silicon nitride, so that the etching rate ratio of the etching solution for etching the silicon nitride to the P-type polycrystalline silicon reaches about 1: 1.

3. The nitro stabilizer in the constant-speed etching solution of the silicon nitride and the P-type polycrystalline silicon can stabilize the oxidation capability of the mononitro compound, so that the mononitro compound can generate long-acting stable controllable oxidation in the etching process, and the etching rate ratio of the etching solution to the silicon nitride to the P-type polycrystalline silicon is stabilized at 1.0 +/-0.1.

4. The constant-speed etching solution for the silicon nitride and the P-type polycrystalline silicon can realize constant-speed etching of the silicon nitride layer and the P-type polycrystalline silicon layer, and the problems that the etching appearance is difficult to control and the etching end point is difficult to judge when two kinds of etching solutions are used for step-by-step etching are solved.

5. The surfactant used in the constant-speed etching solution of the silicon nitride and the P-type polycrystalline silicon ensures that the etching solution has similar wettability (the contact angle difference is less than 2 ℃) to the silicon dioxide hard mask and the silicon substrate, and is favorable for preventing the etching solution from generating difference in etching morphology due to the difference of the upper wettability and the lower wettability when the silicon nitride and the P-type polycrystalline silicon are etched.

Drawings

FIG. 1 is a schematic view of the layered structure of an initial structural layer.

FIG. 2 is a schematic diagram illustrating the etching effect of the etching solution.

FIG. 3 is a photograph showing the contact angle of the etchant to the silicon dioxide layer in example 1.

Fig. 4 is a graph of the contact angle of the etching solution to the silicon substrate in example 1.

FIG. 5 is a photograph showing the contact angle of the etchant with the silicon dioxide layer in comparative example 4.

FIG. 6 is a graph of the contact angle of the etching solution to the silicon substrate in comparative example 4.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

Examples 1 to 11:

the contents of the respective components of examples and comparative examples in accordance with the inventive concept are shown in table 1, and the balance is water.

TABLE 1

The constant-speed etching solution for the silicon nitride and the P-type polycrystalline silicon is prepared by the following steps:

1. taking the raw materials according to the types and the quantities of the raw materials in the table for later use;

2. uniformly mixing a nitro compound and a nitro stabilizer, and adding the mixture into phosphoric acid;

3. adding a surfactant into the mixed solution, uniformly mixing, and ultrasonically dispersing to prepare a constant-speed etching solution of silicon nitride and P-type polycrystalline silicon;

the etching process is carried out according to the following steps:

1. cutting the wafers of Si3N4 and P-type polycrystalline silicon into 1 x 1cm small pieces, washing with water, drying with nitrogen, and measuring the initial thicknesses of the two wafers by using an ellipsometer;

2. heating the etching solution at a constant speed to 158 ℃, etching at a stirring speed of 300r/min, and etching Si3N4 and the P-type polycrystalline silicon for 5min respectively;

3. after etching, the post-etching thicknesses of the two wafers were measured using an ellipsometer after rinsing with water and drying with nitrogen gas immediately, and the etching rates were calculated from the difference between the pre-and post-etching thicknesses and the etching time, and the results are shown in table 2.

TABLE 2

Comparing the above examples and comparative examples, the data shows that the addition of nitro compound can significantly improve the etching rate of P-type polysilicon by the etching solution, and by comparing the data of examples 1 and 4, comparative examples 2 and 3, it can be seen that the addition of nitro stabilizer can effectively stabilize the promotion effect of nitro compound on P-type polysilicon etching, and is beneficial to achieving the purpose of stabilizing the etching rate ratio of silicon nitride layer and P-type polysilicon layer at 1.0 + -0.1, and by comparing the data of examples and 4, the addition of perfluoroalkyl carboxylic acid can level the difference of wettability of the etching solution on silicon dioxide and silicon substrate, and by comparing the data of examples 14 and 15, when adding low boiling point nitro compound, because its boiling point is lower than the working temperature, the volatilization amount of low boiling point nitro compound under the working temperature is increased sharply, the action that can be played is unstable and very limited.

It is apparent that the above embodiments are only examples for clearly illustrating and do not limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications are therefore intended to be included within the scope of the invention as claimed.

Claims

1. The constant-speed etching solution for silicon nitride and P-type polycrystalline silicon is characterized in that the etching solution is an electronic-grade product, and the main components of the etching solution comprise phosphoric acid accounting for 75-88% of the etching solution by mass, 0.01-0.5% of mononitro compound, 0.1-1% of nitro stabilizer, 0.01-0.5% of surfactant and the balance of water.

2. The etching solution of silicon nitride and P-type polysilicon in constant velocity as claimed in claim 1, wherein the phosphoric acid is electronic grade phosphoric acid, nitrate content is less than 0.05ppm, and metal ion content is less than 10 ppb.

3. The etching solution of claim 1, wherein the mononitro compound has a boiling point of > 160 ℃.

4. The etching solution of silicon nitride and P-type polysilicon at a constant speed as claimed in claim 3, wherein the mononitro compound is one or more of 3-nitropyridine, 2-nitroimidazole, 3-nitrobutanol, and 3-nitropropanol.

5. The etching solution of silicon nitride and P-type polysilicon in constant speed as claimed in claim 1, wherein the nitro stabilizer is one or more of N-methylaniline, aniline, N, N-dimethylaniline, and N, N '-dimethyl-N, N' -diphenylurea.

6. The etching solution of claim 1, wherein the surfactant is a perfluoroalkyl carboxylic acid selected from at least one of perfluorooctanoic acid, perfluoropentanoic acid, perfluoroheptanoic acid, perfluorobutanoic acid, perfluorononanoic acid, perfluorodecanoic acid, and perfluoroundecanoic acid.

7. The constant-speed etching solution for silicon nitride and P-type polysilicon according to claim 1, wherein the etching rate ratio of the etching solution to etch silicon nitride and P-type polysilicon is stabilized at 1.0 ± 0.1.