CN-119570491-B - Fluorine-containing etching solution

Abstract

The invention discloses a fluorine-containing silicon nitride etching solution, which comprises phosphoric acid, fluorine-containing compounds, an aluminum oxide etching inhibitor, a tungsten etching inhibitor, a silicon oxide etching inhibitor and deionized water. The etching solution can realize the selective etching of silicon nitride to silicon oxide to aluminum oxide and tungsten in hot phosphoric acid, simultaneously inhibit the etching of silicon oxide, and the etching rate of silicon nitride is more stable at high temperature than that of a phosphoric acid/hydrofluoric acid system due to the complexation slow-release effect of fluorine-containing compounds.

Inventors

• Ban Changsheng
• Fan si
• LUO JIAYANG
• HE ZHAOBO
• ZHANG TING
• FENG KAI
• YE RUI
• LI FEI
• LI SUYUN
• Su Zhangxuan
• YAN FAN

Assignees

• 湖北兴福电子材料股份有限公司

Dates

Publication Date

20260508

Application Date

20241108

Claims (6)

1. 1. The fluorine-containing silicon nitride etching solution is characterized by comprising the following raw materials: 79.5 to 80.5 mass percent of phosphoric acid, and 0.03 to 0.06 mass percent of fluorine-containing compound; 1.5-3.0% by mass of an alumina etching inhibitor, 0.1-0.2% by mass of a tungsten etching inhibitor; 0.3-0.5% of silicon oxide etching inhibitor, and the balance of deionized water; the fluorine-containing compound is one of fluorophosphoric acid, hexafluorophosphoric acid, fluoroboric acid, hexafluoroarsinic acid, hexafluoroantimonic acid, hexafluorozirconic acid and hexafluorotitanic acid; The alumina etching inhibitor is one or more of 3,4, 5-trihydroxybenzoic acid, 2,3, 4-trihydroxybenzoic acid, 2,4, 6-trihydroxybenzoic acid, 3,4, 5-trihydroxybenzamide, 2-phosphonic butane-1, 2, 4-tricarboxylic acid, pyrrole-2, 3, 5-tricarboxylic acid; The tungsten etching inhibitor is one or a combination of a plurality of pyrazole, 1-phenylpyrazole, 4-pyrazolecarboxylic acid, 1,3, 5-trimethylpyrazole, 1-methylpyrazole-5-formic acid, 3, 5-pyrazoledicarboxylic acid and 3, 5-dimethylpyrazole-4-carboxylic acid; the silicon oxide etching inhibitor is silicic acid choline synthesized by taking tetramethoxysilane and choline hydroxide as raw materials, and the structural formula is as follows: 。
2. 2. the fluorine-containing silicon nitride etching solution of claim 1, wherein tetramethoxysilane in the raw material for synthesizing the choline silicate is diluted to a concentration of 25-35% by ethanol aqueous solution, the concentration of the choline hydroxide is 20-30%, the reaction temperature is 70-80 ℃, and the reaction time is 12-24 hours.
3. 3. The fluorine-containing silicon nitride etching solution of claim 2, wherein the tetramethoxysilane in the raw material for synthesizing the choline silicate is diluted to 30% concentration by ethanol aqueous solution, 24% concentration of choline hydroxide, 80 ℃ reaction temperature and 24 hours reaction time.
4. 4. The fluorine-containing silicon nitride etching solution according to claim 1, wherein the etching solution has an operating temperature of 138-148 ℃.
5. 5. The fluorine-containing silicon nitride etching solution according to claim 1, wherein the working temperature of the etching solution is 140-142 ℃.
6. 6. The fluorine-containing silicon nitride etching solution according to claim 1, wherein the etching solution has a SiN/SiO etching selectivity of >2000, a SiN/AlO etching selectivity of >5, and a SiN/W etching selectivity of >100.

Description

Fluorine-containing etching solution Technical Field The invention belongs to the field of electronic chemicals, and particularly relates to a fluorine-containing silicon nitride etching solution. Background The 3D NAND technology solves the limitation caused by 2D or plane NAND flash memory by vertically stacking a plurality of layers of data storage units, has excellent precision, supports higher storage capacity in a smaller space, can manufacture storage equipment with the storage capacity which is up to several times higher than that of the similar NAND technology, further effectively reduces cost and energy consumption, and can comprehensively meet the requirements of numerous consumer mobile equipment and most demanding enterprise deployment. In the manufacturing process of the 3D memory cell, film layers such as tungsten, aluminum oxide, titanium nitride and the like are sequentially deposited in a silicon nitride/silicon oxide laminated layer, and the integrity of the structural layers is ensured in the wet etching process. In particular, the etching rate of high k materials such as alumina in phosphoric acid at high temperature is high, and the etching cannot be completely inhibited by the additive alone, so that the etching rate of silicon nitride in phosphoric acid needs to be further improved in order to improve the etching selectivity of silicon nitride/alumina. The fluorine ions have obvious promotion effect on the etching of the silicon nitride, and the addition of hydrofluoric acid into the high-temperature phosphoric acid can promote the etching rate of the silicon nitride, but hydrogen fluoride is more volatile, so that the etching rate of the silicon nitride is continuously reduced along with the extension of the heating time of the liquid medicine. In order to solve the above problems, it is necessary to prepare a silicon nitride selective etching solution having a stable etching rate by adding a fluorine-containing compound and an inhibitor to phosphoric acid. Disclosure of Invention The invention aims to solve the technical problems of preparing a fluorine-containing etching solution for rapidly etching silicon nitride and simultaneously inhibiting the etching of silicon oxide, aluminum oxide and tungsten. The invention relates to a silicon nitride selective etching solution, which comprises 79.5-80.5% of phosphoric acid, 0.03-0.06% of fluorine-containing compound, 1.5-3.0% of aluminum oxide etching inhibitor, 0.1-0.2% of tungsten etching inhibitor, 0.3-0.5% of silicon oxide etching inhibitor and the balance of deionized water. In the etching solution, the alumina etching inhibitor is one of 3,4, 5-trihydroxybenzoic acid, 2,3, 4-trihydroxybenzoic acid, 2,4, 6-trihydroxybenzoic acid, 3,4, 5-trihydroxybenzamide, 2-phosphonic butane-1, 2, 4-tricarboxylic acid and pyrrole-2, 3, 5-tricarboxylic acid. In the etching solution, the alumina etching inhibitor is chelated on the surface of alumina through a trihydroxy or tricarboxylic acid structure to block the attack of hydronium ions on the active sites of the surface of the alumina, thereby reducing the etching rate of the alumina. In the etching solution, although the aluminum oxide inhibitor is added, the reactivity of hydronium ions in the high-temperature phosphoric acid is at a higher level, and even if the inhibitor exists, the aluminum oxide can be corroded, so that the etching rate of silicon nitride is improved by adding the fluorine-containing compound to improve the SiN/AlO etching selection ratio. In the etching solution, the fluorine-containing compound is one of fluorophosphoric acid, hexafluorophosphoric acid, fluoroboric acid, hexafluoroarsinic acid, hexafluoroantimonic acid, hexafluorozirconic acid and hexafluorotitanic acid. In the etching solution, the fluorine-containing compound is decomposed into hydrogen fluoride in a small part in high-temperature phosphoric acid, so that fluorine ions are ionized to attack silicon nitride, and the etching rate of the silicon nitride is improved. In the etching solution, as the etching reaction is carried out, the hydrogen fluoride is continuously consumed and volatilized, and the lost hydrogen fluoride in the etching solution is continuously supplemented through the dissociation reaction of the fluorine-containing compound, so that compared with the single addition of the hydrogen fluoride, the etching rate of the silicon nitride is reduced more slowly, namely the service life of the etching solution is obviously prolonged. Further, the fluorine-containing compound in the etching solution of the present invention is preferably hexafluorozirconic acid, and the addition amount is preferably 0.04 to 0.05%. In the etching solution, the inhibitor for tungsten etching is one of pyrazole, 1-phenylpyrazole, 4-pyrazolecarboxylic acid, 1,3, 5-trimethylpyrazole, 1-methylpyrazole-5-formic acid, 3, 5-pyrazoledicarboxylic acid and 3, 5-dimethylpyrazole-4-carboxylic acid. In the etching solution, t