CN111925802B

CN111925802B - High-selectivity silicon nitride etching solution, and preparation method and application thereof

Info

Publication number: CN111925802B
Application number: CN202010817298.0A
Authority: CN
Inventors: 王溯; 蒋闯; 季峥; 史筱超
Original assignee: Shanghai Xinyang Semiconductor Material Co Ltd
Current assignee: Shanghai Xinyang Semiconductor Material Co Ltd
Priority date: 2020-08-14
Filing date: 2020-08-14
Publication date: 2021-10-01
Anticipated expiration: 2040-08-14
Also published as: CN111925802A

Abstract

The invention discloses an etching solution, a preparation method and application thereof. The invention provides an etching solution which comprises the following components in parts by weightDividing into: 0.5-10 parts of compound M, 76.5-84.6 parts of phosphoric acid and 13.5-14.9 parts of water. The etching solution of the present invention has a proper etching rate selection ratio for the silicon oxide film and the silicon nitride film, can selectively remove the silicon nitride film, can prolong the service life of the etching solution, and can adapt to the increase of the number of the laminated structure layers.

Description

High-selectivity silicon nitride etching solution, and preparation method and application thereof

Technical Field

The invention relates to an etching solution, a preparation method and application thereof.

Background

Such as a silicon oxide film and such as a silicon nitride film are representative insulator films, and the silicon oxide film or the silicon nitride film may be used alone or in the form of a laminate (laminate) in which one or more thin films are alternately stacked in a semiconductor manufacturing process. In addition, the oxide film or the nitride film is also used as a hard mask for forming a conductive pattern such as a metal wiring.

In the wet etching process for removing the nitride film, an aqueous phosphoric acid solution is generally used. There are many problems with the aqueous phosphoric acid solution alone, such as: the etching rate selection ratio of silicon oxide and silicon nitride is improper, and more particles and precipitates exist in the solution in a short time in the process, so that the service life of liquid medicine is short, the increase of the layer number of the laminated structure cannot be adapted, and the like. In order to solve these problems, it is considered to add an additive to the phosphoric acid aqueous solution to improve the etching capability of the phosphoric acid aqueous solution.

Disclosure of Invention

The technical problem to be solved by the invention is that the etching rate selection ratio of the existing etching solution to the silicon oxide film and the silicon nitride film is not proper. The invention provides an etching solution, a preparation method and application thereof. The etching solution can selectively remove the silicon nitride film, prolongs the service life of the etching solution, and can adapt to the increase of the number of layers of the laminated structure.

The present invention mainly solves the above-mentioned problems by the following technical means.

The invention provides an etching solution which comprises the following components in parts by weight: 0.5-10 parts of compound M, 76.5-84.6 parts of phosphoric acid and 13.5-14.9 parts of water;

in a preferred embodiment, the etching solution comprises the following components in parts by weight: 0.5-10 parts of compound M, 76.5-84.6 parts of phosphoric acid and 13.5-14.9 parts of water

In a preferred embodiment, the compound M is present in an amount of 0.5 to 10 parts by weight, for example 0.5, 1.0, 4.5, 9.5 or 10 parts by weight, preferably 1 to 9.5 parts by weight, more preferably 4.5 parts by weight.

In a preferred embodiment, the weight fraction of the phosphoric acid is 76.4 to 84.6 parts; such as 76.4 parts, 76.9 parts, 81.2 parts, 84.2 parts, or 84.6; preferably 76.9 to 81.2 parts; more preferably 81.2 parts.

In a preferred embodiment, the water is present in an amount of 13.5 to 14.9 parts, for example 13.5 parts, 13.6 parts, 14.3 parts, 14.8 parts or 14.9 parts, preferably 13.6 to 14.8 parts, more preferably 14.3 parts by weight.

In a preferred embodiment, the etching solution comprises the following components in percentage by mass: 0.5% -10% of compound M, 76.5% -84.6% of phosphoric acid and 13.5% -14.9% of water.

In a preferred embodiment, the etching solution comprises the following components in percentage by mass: 0.5% -10% of compound M, 76.5% -84.6% of phosphoric acid and the balance of water.

In a preferred embodiment, the mass percent of the compound M is 1.0-9.5%; preferably 4.5% to 9.5%, more preferably 4.5%.

In a preferred embodiment, the mass percentage of the phosphoric acid is 76.5% -84.2%; preferably 76.9% -81.2%; more preferably 81.2%.

In a preferred embodiment, the mass percent of the water is 14% -14.8%; preferably 14.3% -14.8%; more preferably 14.3%.

In a preferred embodiment, the etching solution comprises the following components in percentage by mass: 0.5% of compound M, 84.6% of phosphoric acid and 14.9% of water.

In a preferred embodiment, the etching solution comprises the following components in percentage by mass: 4.5% of compound M, 81.2% of phosphoric acid and 14.3% of water.

In a preferred embodiment, the etching solution comprises the following components in percentage by mass: 1% of compound M, 84.2% of phosphoric acid and 14.8% of water.

In a preferred embodiment, the etching solution comprises the following components in percentage by mass: 9.5% of compound M, 76.9% of phosphoric acid and 13.6% of water.

In a preferred embodiment, the etching solution comprises the following components in percentage by mass: 10% of compound M, 76.5% of phosphoric acid and 13.5% of water.

In a preferred embodiment, the mass ratio of the compound M to the phosphoric acid is 1: (7.65-169); preferably 1: (8-77); more preferably 1: (8-18); also preferably, 1: 18.

in a preferred embodiment, the water is selected from one or more of deionized water, distilled water, pure water and ultrapure water.

In a preferred embodiment, the etching solution is an etching solution for etching a silicon nitride film.

In a preferred embodiment, when the etching solution is an etching solution for etching a silicon nitride film, the etching is performed in the presence of a silicon oxide film. The silicon nitride film may be a silicon nitride film formed on a patterned silicon semiconductor wafer. The thickness of the silicon nitride film can be

. The silicon oxide film may be a silicon oxide film formed on a patterned silicon semiconductor wafer; the thickness of the silicon oxide film is

. The silicon oxide film and the silicon nitride film are of a laminated structure of the silicon oxide film and the silicon nitride film, and the number of layers of the laminated structure can be 10-200.

The invention also provides a preparation method of the etching solution, which comprises the following steps of mixing the components of the etching solution. The compound M is preferably added into the phosphoric acid aqueous solution in a mixing mode of the components, and the mixture is uniformly stirred.

The raw materials in the etching solution can also be stored in a packaged form of a plurality of independent components.

The invention also provides application of the etching solution in etching silicon nitride films and/or silicon oxide films. The silicon nitride film may be a silicon nitride film formed on a silicon semiconductor wafer. The silicon nitride film may be a silicon nitride film formed on a patterned silicon semiconductor wafer. The thickness of the silicon nitride film can be

. The silicon oxide film may be a silicon oxide film formed on a silicon semiconductor wafer. The silicon oxide film may be a silicon oxide film formed on a patterned silicon semiconductor wafer. The thickness of the silicon oxide film may be

。

In one embodiment, when the etching is in the presence of a silicon oxide film and a silicon nitride film, the silicon oxide film and the silicon nitride film are a stacked structure of a silicon oxide film and a silicon nitride film. When the etching is in the presence of a silicon oxide film and a silicon nitride film, the etching selectively etches the silicon oxide film. In the laminated structure, the thickness of the silicon oxide film may be set to

The thickness of the silicon nitride film can be

. In the laminated structure, the number of layers of the laminated structure can be 10-200, such as 32, 64, 128 or 192.

In one embodiment, the application comprises the steps of: and soaking the silicon wafer with the silicon oxide film and/or the silicon nitride film in the etching solution, taking out the wafer, cleaning and drying.

The temperature of the soaking may be a temperature conventional in the art, preferably 100-180 ℃, more preferably 150-165 ℃, and most preferably 157-161 ℃.

The soaking time may be a time conventional in the art, preferably 1-30min, more preferably 5-20min, most preferably 8-15min (e.g., 10 min).

The invention also provides the application of the compound M as an etching solution additive;

the mass percentage of the compound M in the etching solution can be 0.01-10%, such as 1.0-9.5%; also for example 4.5% -9.5%, more for example 4.5%.

In the application, the etching solution can be an etching solution for etching a silicon nitride film, and the etching can be performed in the presence of a silicon oxide film. The silicon nitride film and the silicon oxide film may be defined as described above.

In the present invention, "room temperature" means 20 to 40 ℃ unless otherwise specified.

The above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention without departing from the common general knowledge in the art.

The phosphoric acid used in the invention is a concentrated phosphoric acid aqueous solution with the mass percentage of 85%. In the case of other concentrations of concentrated phosphoric acid, the amount of concentrated phosphoric acid converted to that concentration can be calculated by equivalent amounts.

The concentration of each component in the etching solution is mass percent, namely the mass of each component accounts for the total mass of the etching solution.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows: the etching solution of the invention has proper etching rate selection ratio of the silicon oxide film and the silicon nitride film when etching, can selectively remove the silicon nitride film, prolongs the service life of the etching solution and can adapt to the increase of the number of laminated structures.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

1. Preparation of etching solution

Structure of compound M:

structure of compound N:

compound M and compound N were prepared according to patent CN 108884116A;

respectively adding a compound M or N into a phosphoric acid raw material at room temperature to obtain etching solutions in examples 1-5 and comparative example 1; the etching solution in comparative example 2 was a phosphoric acid raw material.

The raw materials of the phosphoric acid used in the invention are all concentrated phosphoric acid with the mass percentage of 85 percent. In the case of other concentrations of concentrated phosphoric acid, the amount of concentrated phosphoric acid converted to that concentration can be calculated by equivalent amounts.

The concentration of the additive (compound M or compound N) in the invention is mass percent, i.e. the mass of the additive accounts for the total mass of the etching solution.

Examples 1 to 5, comparative examples 1 to 2

TABLE 1 percentage of compound M or compound N in the etching solution to the total mass of the etching solution

	Addition amount of Compound M or Compound N
		Example 1	4.5% Compound M
Example 2	1.0% Compound M
		Example 3	9.5% Compound M
Example 4	0.5% Compound M
		Example 5	10% Compound M
Comparative example 1	4.5% Compound N
		Comparative example 2	━

2. Etching experiment

Method for detecting etching rate

Etching an object: a silicon oxide film and a silicon nitride film; wherein the two films are deposited on the patterned silicon semiconductor wafer to a thickness of

And forming a deposit on the patterned silicon semiconductor wafer to a thickness of

The silicon nitride film of (1).

Etching temperature: 159 ℃ plus or minus 2 ℃.

Etching container: a quartz tank.

Etching time: the silicon oxide film and the silicon nitride film were etched for 720 seconds and 6000 seconds, respectively.

The speed measurement method comprises the following steps: the film thicknesses of the silicon oxide film and the silicon carbide film were measured before and after etching using a film thickness measuring apparatus (NANO VIEW, SEMG-1000), and the etching rate was calculated by dividing the difference between the initial thickness and the thickness after etching by the etching time (minutes). The selectivity ratio represents the ratio of the silicon carbide film etching rate (SiNE/R) to the oxide film etching rate (SiO E/R).

Initial silica concentration: 0ppm of

② method for detecting service life

In both of silicon oxide film etching and silicon nitride film etching, the etching metabolite contains silicon dioxide, and the concentration of silicon dioxide dissolved in the etching solution gradually increases as the etching time increases. Thus, an etching solution in which the concentration of silicon dioxide was gradually increased (0ppm/80ppm/120ppm/300ppm/500ppm) was prepared as an initial etching solution, and the etching rates and the selectivity of silicon oxide and silicon nitride films were measured, respectively.

After dissolving silicon dioxide with different concentrations in the etching solutions of examples 1 to 5 and comparative examples 1 and 2, etching experiments were performed, and the etching rates of the silicon oxide film and the silicon nitride film were respectively measured and selected as follows:

application examples 1 to 7

The etching rates and selectivity of the silicon oxide film and the silicon nitride film etched using the etching solutions of examples 1 to 5 and comparative examples 1 and 2 at an initial silicon dioxide concentration of 0ppm are shown in Table 2:

TABLE 2 etch rates and selectivity ratios for silicon oxide and silicon nitride films at an initial silicon dioxide concentration of 0ppm

Application examples 8 to 14

The etching rates and selectivity of the silicon oxide film and the silicon nitride film etched using the etching solutions of examples 1 to 5 and comparative examples 1 and 2 at an initial silicon dioxide concentration of 80ppm are detailed in Table 3:

TABLE 3 etch rates and selectivity for silicon oxide and silicon nitride films at an initial silicon dioxide concentration of 80ppm

Application examples 15 to 21

The etching rates and selectivity ratios of the silicon oxide film and the silicon nitride film etched using the etching solutions of examples 1 to 5 and comparative examples 1 and 2 at an initial silicon dioxide concentration of 120ppm are detailed in Table 4:

TABLE 4 etch rates and selectivity ratios for silicon oxide and silicon nitride films at an initial silicon dioxide concentration of 120ppm

Application examples 22 to 28

The etching rates and selectivity ratios of the silicon oxide film and the silicon nitride film etched using the etching solutions of examples 1 to 5 and comparative examples 1 and 2 at an initial silicon dioxide concentration of 300ppm are detailed in Table 5:

TABLE 5 etch rates and selectivity for silicon oxide and silicon nitride films at an initial silicon dioxide concentration of 300ppm

Application examples 29 to 35

The etching rates and selectivity of the silicon oxide film and the silicon nitride film etched using the etching solutions of examples 1 to 5 and comparative examples 1 and 2 at an initial silicon dioxide concentration of 500ppm are shown in Table 6:

TABLE 6 etch rates and selectivity for silicon oxide and silicon nitride films at an initial silicon dioxide concentration of 500ppm

Note: within the error range of the experimental system of the present invention, the selection ratio interval is preferably 500-900. The selection ratio is less than 229 and is an over-etching selection ratio; the selection ratio less than 281 is the selection ratio of the skip moment; the selection ratio is greater than 939 and is slightly rewound; a selectivity greater than 1131 is the strikethrough selectivity.

From the above experimental results of application examples 1-35, it can be seen that the etching solutions of examples 1-3 have good selectivity when the selectivity of the initial silicon dioxide is 0ppm, 0ppm, 120ppm, 300ppm or 500ppm, respectively, and is within 500-900. Example 4 the selectivity of 375-469 in etching was slightly over-etched when the initial silicon dioxide was 0ppm, 0ppm, 120ppm, 300ppm or 500ppm, respectively, and the selectivity was superior to that of comparative example 2. Example 5 the selectivity of 926-979 in etching was slightly sticky back when the initial silica was 0ppm, 0ppm, 120ppm, 300ppm or 500ppm, respectively, which was significantly weaker than that of comparative example 1. The etchant of comparative example 1 has a severe phenomenon of sticking back, and the addition of compound N to phosphoric acid causes the etchant to have a severe phenomenon of sticking back. In comparative example 2, there was a severe over-etching phenomenon due to no addition of the additive. In summary, the compound M is added to the phosphoric acid to reduce the over-etching phenomenon of the etching solution, and the compound M is added in an amount of 1.0-9.5% by mass to achieve a better selection ratio of the etching solution.

(iii) etching of laminated structures with different layers

Etching an object: silicon wafer having a cross-laminated structure of

And a silicon oxide layer of

The silicon nitride layers of (2) are cross-laminated. The number of layers of the laminated structure is respectively as follows: 32 layers/64 layers/128 layers/192 layers.

Etching conditions: the initial concentration of silicon dioxide in the etching solution was 0ppm

The detection method comprises the following steps: after etching the wafer at 159 ℃. + -. 2 ℃ for 10min, the wafer was taken out, washed, dried and the etching of the layered structure in the wafer was observed by TEM section.

Evaluation criteria: the A level is the etching completion of the silicon nitride layer and the silicon oxide layer is not damaged; the B level is the silicon nitride layer which is etched but damaged; the C level is that the silicon nitride layer is not etched.

Application examples 36 to 42

The etching experiments were carried out using the etching solutions of examples 1 to 5 and comparative examples 1 and 2, and the etching results are shown in Table 7:

TABLE 7 etching results of silicon wafers having a cross-laminated structure

From the results of practical examples 36 to 42, it was found that the etching of the 32-, 64-and 128-layer silicon wafers was completed by the etching solutions of practical examples 1 to 3 and the silicon oxide layers were not damaged. The etching solution in example 4 was subjected to the above-described etching experiment to etch the silicon nitride layer of the silicon wafer of 32, 64 and 128 layers but damage the silicon oxide layer. The etching solutions in example 5 and comparative example 1 were subjected to the above-described etching experiment to finish etching of the silicon nitride layer. The etching solution in comparative example 2 was subjected to the above-described etching experiment to completely etch the silicon nitride layers of the 32-layer and 64-layer silicon wafers but to damage the silicon oxide layers and to leave the silicon nitride layers of the 128-layer silicon wafers unetched.

Claims

1. An etching solution comprises the following components in parts by weight: 1-9.5 parts of compound M, 76.5-84.6 parts of phosphoric acid and 13.5-14.9 parts of water;

。

2. the etching solution according to claim 1, wherein the etching solution is an etching solution for etching a silicon nitride film;

and/or the mass ratio of the compound M to the phosphoric acid is 1: (8-77).

3. The etching solution of claim 2, wherein the mass ratio of the compound a to the phosphoric acid is 1: 8-1: 18.

4. the etching solution according to claim 3, wherein the mass ratio of the compound A to the phosphoric acid is 1: 18.

5. the etching solution of claim 2, wherein the compound M is present in an amount of 1.0 part, 4.5 parts, or 9.5 parts by weight;

and/or the weight fraction of phosphoric acid is 76.5 parts, 76.9 parts, 81.2 parts, 84.2 parts or 84.6;

and/or the weight fraction of the water is 13.5 parts, 13.6 parts, 14.3 parts, 14.8 parts or 14.9 parts;

and/or, when the etching solution is used for etching a silicon nitride film, the etching is carried out in the presence of a silicon oxide film;

and/or, when the etching solution is an etching solution for etching a silicon nitride film, the silicon nitride film is a silicon nitride film formed on a patterned silicon semiconductor wafer;

and/or, when the etching solution is used for etching a silicon nitride film, the thickness of the silicon nitride film is 50A-5000A.

6. The etching solution of claim 5, wherein the compound A is present in an amount of 4.5 parts by weight;

and/or the weight fraction of the phosphoric acid is 76.9 to 81.2;

and/or the weight fraction of the water is 13.6-14.8 parts.

7. The etching solution according to claim 6, wherein the weight fraction of phosphoric acid is 81.2 parts;

and/or the weight fraction of the water is 14.3 parts.

8. The etching solution according to any one of claims 1, 2 or 5, wherein the mass percent of the compound M is 4.5% -9.5%;

and/or the mass percent of the phosphoric acid is 76.5-84.2%;

and/or the mass percent of the water is 14-14.8%;

and/or the water is selected from one or more of deionized water, distilled water, pure water and ultrapure water;

and/or, when the etching solution is an etching solution for etching a silicon nitride film, the etching is performed in the presence of a silicon oxide film, the silicon oxide film being a silicon oxide film formed on a patterned silicon semiconductor wafer;

and/or, when the etching solution is an etching solution for etching a silicon nitride film, the etching being performed in the presence of a silicon oxide film, the silicon oxide film having a thickness of 50A-500A;

and/or when the etching solution is used for etching the silicon nitride film and the etching is carried out in the presence of the silicon oxide film, the silicon oxide film and the silicon nitride film are of a laminated structure of the silicon oxide film and the silicon nitride film, and the number of layers of the laminated structure is 10-200.

9. The etching solution according to claim 8, wherein the mass percent of the compound A is 4.5%;

and/or the mass percent of the phosphoric acid is 76.9-81.2%;

and/or the mass percent of the water is 14.3-14.8%.

10. The etching solution according to claim 9, wherein the phosphoric acid is 81.2% by mass;

and/or the mass percentage of the water is 14.3 percent.

11. The etching solution according to claim 1, wherein the etching solution comprises the following components in percentage by mass according to any one of scheme 1, scheme 2 or scheme 3;

scheme 1, 4.5% compound M, 81.2% phosphoric acid and 14.3% water;

scheme 2, 1% compound M, 84.2% phosphoric acid and 14.8% water;

scheme 3, 9.5% compound M, 76.9% phosphoric acid and 13.6% water.

12. Use of an etching solution according to any one of claims 1 to 11 for etching silicon nitride films and/or silicon oxide films.

13. The use according to claim 12, characterized in that said use comprises the following steps: soaking the silicon wafer with the silicon oxide film and/or the silicon nitride film in the etching solution, taking out the wafer, cleaning and drying;

and/or, the silicon nitride film is formed on a silicon semiconductor wafer;

and/or, the silicon oxide film is formed on a silicon semiconductor wafer;

and/or, when the etching is in the presence of a silicon oxide film and a silicon nitride film, the etching selectively etches the silicon oxide film;

and/or, when the etching is performed in the presence of a silicon oxide film and a silicon nitride film, the silicon oxide film and the silicon nitride film have a laminated structure of the silicon oxide film and the silicon nitride film.

14. The use of claim 13, wherein the silicon nitride film has a thickness of 50 a-5000 a;

and/or, the silicon nitride film is a silicon nitride film formed on a patterned silicon semiconductor wafer;

and/or, the silicon oxide film is formed on a patterned silicon semiconductor wafer;

and/or the thickness of the silicon oxide film is 50A-500A;

and/or the number of layers of the laminated structure is 10-200;

and/or the soaking temperature is 100-180 ℃;

and/or, the soaking time is 1-30 min.

15. The application of a compound M as an etching solution additive;

。