Method for purification of etching solution
AssigneeNisso Engineering Co., Ltd.
InventorsAkira Nakada, Akira Yoneya, Noriyuki Kobayashi, Mamoru Katayanagi, Tsutomu Kawashima, Hiroshi Yoshida
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Abstract
A method for purifying an etching solution consisting of an aqueous phosphoric acid solution which has been used in etching of a silicon nitride film. In the process, hydrogen fluoride is added to an etching solution consisting of an aqueous phosphoric acid solution which has been used for etching of a silicon nitride film, and the resulting solution is heated to remove fluorides of silicon as reaction products of hydrogen fluoride with silicon compounds which have been contained in the etching solution together with vaporized water.
Claims9
A method for purifying an etching solution consisting of an aqueous phosphoric acid solution which has been used for etching of a silicon nitride film formed on a semiconductor wafer and contains silicon compounds resulting from the etching, said method comprising:
- adding hydrogen fluoride in an amount of 6 moles or more per mole of said silicon compounds, in terms of silicon dioxide, and, if necessary, additional water, to an etching solution, said etching solution consisting of an aqueous phosphoric acid solution which has been used for etching of a silicon nitride film formed on a semiconductor wafer and contains silicon compounds resulting from the etching, and
- heating the resulting solution to evaporate water in an amount more than a thousand times of the weight of silicon content to be removed and to remove fluorides of silicon as reaction products of the silicon compounds with hydrogen fluoride together with vaporized water.
Dependencies are inferred from the claim text.