Method for analyzing mixed acid concentration of silicon etching solution

Abstract

The invention discloses a method for analyzing the mixed acid concentration of a silicon etching solution. The method comprises the steps of taking a mixed acid sample of nitric acid, hydrofluoric acid and acetic acid to be detected, respectively adding an aprotic organic solvent and an anti-precipitation interference solvent into the mixed acid sample to prepare a silicon etching mixed acid solution, and dropwise adding a calibrated strong alkali aqueous solution into the silicon etching mixed acid solution through an automatic potentiometric titrator until a first jump part, a second jump part and a third jump part respectively appear; and calculating the concentration of the silicon etching liquid mixed acid, namely nitric acid, hydrofluoric acid and acetic acid, according to the volumeof the strong alkali aqueous solution consumed by the midpoints of the first, second and third jump parts. The concentrations of nitric acid, hydrofluoric acid and acetic acid contained in the silicon etching solution are easily, quickly and accurately measured by a one-step method, automatic dropwise adding and automatic calculation of the titration result are realized; the method is efficient and quick, the precision is improved, and time and labor are saved.

Description

technical field [0001] The invention relates to a method for analyzing the mixed acid concentration of silicon etching solution. Background technique [0002] Silicon etching is an important process in the manufacture and packaging of semiconductor integrated circuits. Generally speaking, the manufacturing process of integrated circuits takes place at tens of nanometers to several microns on the surface of the wafer material. Hundreds of processes will be performed on the surface of the wafer, including the back etching of the silicon wafer. The acid etchant used is mostly Below is a mixture of strong acids (hydrofluoric, nitric, and acetic). If the acid concentration is too high, it will cause over-cutting, which will cause insufficient driving current and poor display. If the acid concentration is too low, it will cause insufficient etching and reduce the aperture ratio, which will seriously affect the quality of etching. The higher precision of formation requires the mi...

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Problems solved by technology

If the acid concentration is too high, it will cause over-cutting, which will cause insufficient driving current and poor display. If the acid concentration is too low, it will cause insufficient etching and reduce the aperture ratio, which will seriously affect the quality of etching. The high precision of the formation gradually requires the miniaturization of the width of the pattern formation. For this, there is a stricter requirement for the concentration accuracy of hydrofluoric acid, nitric acid, and acetic acid.

[0003] Chinese patent CN 107796912A discloses a mixed acid that uses an aprotic polar organic solvent (alcohol, isopropanol, acetone, tetrahydrofuran, methyl ethyl ketone or dimethylpyrrolidone) to dilute hydrofluoric acid and nitric acid, and uses sodium hydroxide or potassium hydroxide Solution titrant carries out potentiometric titration to mixed acid to obtain the concentration of hydrofluoric acid and nitric acid in mixed acid; Monohydric alcohols (methanol or ethanol) and dihydric alcohols (ethylene glycol, 1,2-propanediol or 1,4-butanediol) are non-aqueous media of mixed acids, and potentiometric titration of mixed acid solutions of nitric acid, phosphoric acid and acetic acid, However, the preparation of a strong alkali-ethanol solution requires static precipitation for 30 days, which is cumbersome and time-consuming; in addition, under alkaline conditions, methanol or ethanol and acetic acid will generate ethyl acetate or methyl acetate, which precipitates out of the solution, and the resulting precipitate is harmful to the environment. The detection electrode produces interference which affects the detection result

However, the mixed acid composed of nitric acid, hydrofluoric acid and acetic acid and its content test are rarely reported. Xie Guoqing, Zhu Qi and others used the spectroscopic method to test the content of nitric acid, and used hydrofluoric acid to generate calcium fluoride precipitation to test hydrofluoric acid. Acid content, potentiometric titration method to test the total acid content, so as to obtain the acetic acid content (three methods combined to test the composition of nitric acid-hydrofluoric acid-acetic acid mixed acid, Guangzhou Chemistry, Vol.43 No.5, 2018.10) This method is cumbersome and increases Uncertainty of the results, in addition, the accuracy of the spectroscopic method for testing the concentration of nitric acid is not enough

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