Polycrystalline silicon etching solution

Abstract

The invention relates to a polycrystalline silicon etching solution, which is prepared from the following components in percentage by mass: 0.1 to 2.38 percent of quaternary ammonium salt compounds, 1 to 40 percent of alcohol amine compounds, 1 to 40 percent of polyhydric alcohol compounds, 0.1 to 2 percent of etching accelerant and the balance of deionized water. The sum of the parts by weight of the components is 100%. The alcohol amine compound and the polyhydric alcohol compound have a synergistic effect, so that the etching rate of SiO2 can be effectively reduced; the etching accelerator can improve the etching rate of the polycrystalline silicon, improve the etching uniformity and improve the surface roughness of the polycrystalline silicon.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor material etching, and in particular relates to a polysilicon etching solution. Background Art

[0002] In advanced semiconductor manufacturing processes, it is necessary to etch polysilicon with tiny line widths, and at the same time, it is necessary to reduce the corrosion of silicon dioxide and dielectric layer structures. Therefore, polysilicon etching solutions with specific properties are required in advanced semiconductor manufacturing.

[0003] Alkaline polysilicon etching solutions generally use potassium hydroxide and tetramethylammonium hydroxide as the main system, but potassium hydroxide is easy to introduce metal ions, and TMAH is more often used as the main component of polysilicon etching solutions in advanced processes. However, TMAH also has disadvantages such as low etching rate and high toxicity to the human body. Therefore, it is of great significance to develop an etching solution with low organic base concentration, fast etching rate for polysilicon, and high polysilicon / silicon dioxide (Poly / SiO2) selectivity.

[0004] In the prior art, Chinese patent application number 202210252495.1 discloses a silicon etching solution and an etching method. The etching solution is a mixture of TMAH, TEAH and polar protic solvents such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, etc., which can effectively inhibit the etching rate of SiO2 and improve the selectivity of Poly / SiO2. Chinese patent application number 202010015570 discloses a silicon etching solution and an etching method. The aqueous solution of quaternary ammonium salt compounds and ketal compounds can reduce the etching rate of SiO2, and the selectivity of Si / SiO2 is greater than 500:1. However, the above-mentioned etching solution will inhibit the etching rate of polysilicon while inhibiting the etching of SiO2.

[0005] TMAH is a neurotoxin. High concentrations of TMAH seriously endanger the lives of workers. However, low concentrations of TMAH have a low etching rate for polysilicon, and the selectivity of Poly / SiO2 is less than 300:1. In addition, TMAH etching of polysilicon has the characteristics of uneven etching, which makes it difficult to meet the requirements of safe and efficient production at the same time. The silicon etching solutions described in the above patents can only solve some problems and cannot meet all the requirements of polysilicon etching. Summary of the invention

[0006] In order to solve the above problems, the present invention aims to provide a polysilicon etching solution, which has a low concentration of quaternary ammonium salt compounds and can quickly etch polysilicon thin films.

[0007] The technical solution of the present invention is as follows: One of the purposes of the present invention is to provide a polysilicon etching solution that can quickly etch polysilicon thin films.

[0008] The second object of the present invention is to provide a polysilicon etching solution that can inhibit the corrosion of SiO2 and make the selection ratio of Poly / SiO2 greater than 1000:1.

[0009] The third object of the present invention is to provide a polysilicon etching solution that can make etching more uniform and reduce the surface roughness of the polysilicon after etching.

[0010] To achieve the above-mentioned purpose, the technical solution of the present invention provides a polysilicon etching solution, which comprises the following components in mass percentage: 0.1-2.38% quaternary ammonium salt compound, 1-40% alcohol amine compound, 1-40% polyol compound, 0.1-2% etching accelerator, and the balance is deionized water.

[0011] Preferably, the polysilicon etching solution comprises the following components by mass fraction: 0.1-2.38% of quaternary ammonium salt compounds, 10-40% of alcohol amine compounds, 5-30% of polyol compounds, 0.3-1% of etching accelerators, and the balance is deionized water.

[0012] Further preferably, the polysilicon etching solution comprises the following components by mass fraction: 0.5-2.1% quaternary ammonium salt compound, 20-30% alcohol amine compound, 10-20% polyol compound, 0.4-0.6% etching accelerator, and the balance is deionized water. Preferably, the quaternary ammonium salt compound is a combination of at least one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and choline hydroxide.

[0013] Preferably, the alcoholamine compound is a combination of at least one or more of monoethanolamine, propanolamine, isopropanolamine, diethanolamine, diglycolamine, triethanolamine and triisopropanolamine.

[0014] Preferably, the polyol compound is a combination of at least one or more of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, and diethylene glycol.

[0015] Preferably, the etching accelerator is a halogen element, including at least one or more of Cl2, Br2, I2, and a combination thereof.

[0016] Preferably, the etching accelerator is an amine or nitrogen heterocyclic compound, including: tris (hydroxymethyl) aminomethane (Tris), aminopyrazine, piperidine, pyrimidine, trimethoprim (TMP), acridine, 9,10-dihydroacridine, 3,6-diaminoacridine, 2-chloro-10-methylacridine, 3-ethyl-5,8-diaminoacridine lactate, 1,10-phenanthroline, phenazine, dihydrophenazine, 2,3-diaminophenazine, 2-hydroxyphenazine, 2-hydroxy-3-aminophenazine, imidazophenazine lactam, melamine, isothiazole, benzothiadiazole, phenothiazine, phenoxazine, at least one or more combinations thereof.

[0017] The preparation method of the polysilicon etching solution comprises the following steps: adding deionized water, electronic grade quaternary ammonium salt aqueous solution, electronic grade alcohol amine, electronic grade polyol and etching accelerator into a mixing kettle in sequence, and circulating and filtering for more than 2 hours.

[0018] The advantages and beneficial effects of the present invention are as follows: in the present invention, the synergistic effect of the amine compound and the polyol can effectively inhibit the etching of SiO2, and the etching rate of Poly can be increased by adding an etching accelerator, so that the selectivity ratio of Poly / SiO2 can be greater than 1000:1, and the etching uniformity can be improved and the surface roughness of polysilicon can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a macroscopic morphology of the Poly test piece after etching in Comparative Example 2; Figure 2 is a macroscopic morphology of the Poly test piece after etching in Example 8; Figure 3 is a microscopic morphology of the Poly test piece after etching in Comparative Example 2; Figure 4 This is a microscopic morphology of the Poly test piece after etching in Example 8. DETAILED DESCRIPTION

[0020] In order to better understand the present invention, the present invention is further described in detail below in conjunction with diagrams and examples, but the scope of protection claimed in the present invention is not limited to the following examples.

[0021] The etching solution of the present invention can be prepared by simply and evenly mixing the components described in Table 1.

[0022] Table 1 shows the components and contents of the etching solutions of Examples 1 to 16 and Comparative Examples 1 to 8

[0023] Cut the Poly test piece into 1*1 cm 2The test piece was immersed in HF at 200:1 for 2 minutes to remove the surface oxide layer, and then immersed in 60℃ solution for 20 seconds. After washing with deionized water and drying with N2, the etching thickness was measured with a gyrograph and the etching rate was calculated. The SiO2 test piece was cut into 1*1 cm 2 The test piece was immersed in a 60℃ solution for 60 min, washed with deionized water and dried with N2, and then the etching thickness was measured with a gyrograph and the etching rate was calculated.

[0024] The results of the examples and comparative examples are summarized in Table 2.

[0025] Table 2 shows the etching rates and selectivities of different film layers in Examples 1 to 16 and Comparative Examples 1 to 8.

[0026] The etched Poly test piece was observed for macroscopic and microscopic morphology using an ultra-depth-of-field microscope and AFM, respectively. Figure 1 and Figure 2 They are macroscopic morphology pictures of comparative example 2 and example 8, respectively. The color of the test piece of example 8 is more uniform, that is, the etching is more uniform. Figure 3 and Figure 4 The microscopic morphology diagrams are respectively those of comparative example 2 and example 8. The Ra of example 6 is smaller, that is, the surface roughness is smaller. The additive can increase the etching rate by its oxidizing property or by enhancing the alkalinity of the solution, and can also improve the uniformity of etching.

[0027] According to the experimental results of the above embodiments, it can be seen that the etching solution provided by the present invention can quickly etch the Poly film at 60°C, while inhibiting the etching of SiO2, achieving a Poly / SiO2 selectivity ratio greater than 1000:1, and has higher etching uniformity and smaller surface roughness.

[0028] The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A polysilicon etching solution, characterized in that: The polysilicon etching solution contains the following components by mass percentage: 0.1~2.38% quaternary ammonium salt compound, 1~40% alcohol amine compound, 1~40% polyol compound, 0.1~2% etching accelerator, and the balance is deionized water.

2. The polysilicon etching solution according to claim 1, characterized in that: The polysilicon etching solution contains the following components by mass percentage: 0.1~2.38% quaternary ammonium salt compound, 10~40% alcohol amine compound, 5~30% polyol compound, 0.3~1% etching accelerator, and the balance is deionized water.

3. The polysilicon etching solution according to claim 1, characterized in that: The polysilicon etching solution contains the following components by mass percentage: 0.5~2.1% quaternary ammonium salt compound, 20~30% alcohol amine compound, 10~20% polyol compound, 0.4~0.6% etching accelerator, and the balance is deionized water.

4. The polysilicon etching solution according to claim 1, characterized in that: The quaternary ammonium salt compound is a combination of at least one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and choline hydroxide.

5. The polysilicon etching solution according to claim 1, characterized in that: The alcoholamine compound is a combination of at least one or more of monoethanolamine, propanolamine, isopropanolamine, diethanolamine, diglycolamine, triethanolamine and triisopropanolamine.

6. The polysilicon etching solution according to claim 1, characterized in that: The polyol compound is a combination of at least one or more of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, and diethylene glycol.

7. The polysilicon etching solution according to claim 1, characterized in that: The etching accelerator is a halogen element, including at least one or more of Cl2, Br2, and I2.

8. The polysilicon etching solution according to claim 1, characterized in that: The etching accelerator is an amine or nitrogen heterocyclic compound, including: tris(hydroxymethyl)aminomethane, aminopyrazine, piperidine, pyrimidine, trimethoprim, acridine, 9,10-dihydroacridine, 3,6-diaminoacridine, 2-chloro-10-methylacridine, 3-ethyl-5,8-diaminoacridine lactate, 1,10-phenanthroline, phenazine, dihydrophenazine, 2,3-diaminophenazine, 2-hydroxyphenazine, 2-hydroxy-3-aminophenazine, imidazophenazine lactam, melamine, isothiazole, benzothiadiazole, phenothiazine, phenoxazine, at least one or more combinations thereof.

9. The method for preparing the polysilicon etching solution according to any one of claims 1 to 8, characterized in that: Deionized water, electronic grade quaternary ammonium salt, alcohol amine, polyol and etching accelerator are added to a mixing kettle in sequence, and circulated and filtered for more than 2 hours to obtain a polysilicon etching solution.

Images