반도체 웨이퍼 製造工程 중 發生廢酸으로부터 Na₂SiF6 및 초산의 回收에 관한 硏究
Study on recovery of Na₂SiF6 and acetic acid from waste acid produced during semiconductor wafer process
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초록
반도체 웨이퍼 제조 공정 중 발생하는 질산, 불산, 초산으로 구성된 혼산을 재활용하기 위한 연구를 수행하였다. 초기에 NaNO₃ 와 Na₂SiO₃를 사용하여 불산을 Na₂SiF6로 침전시켜 회수하였고, 이 때 혼산 중 불산의 농도는 초기 110 g/L에서 0.5 g/L로 낮아져 불산 회수율은 99.5%였다. 불산회수 후 남은 혼산의 질산과 초산의 농도는 각각 498 g/L, 265 g/L였고, 이 혼산을 2단계 분별증류법에 의해 분리 • 회수하였다. 1단계에서는 초산을 증류하여 질산과 분리해내고, 2단계에서는 증류된 초산 중 잔류하는 미량의 질산을 제거하여 순수 초산만을 회수하였다. 회수된 초산의 농도는 약 20%였고, 최종회수율은 약 87.5%이었다.
Abstract
We researched recycle of mixed waste acids including HF, CH₃COOH, HNO₃ produced during semiconductor wafer process. At first, we recovered HF in form of Na2SiF6 by precipitation using NaNO₃ and Na₂SiO₃. Concentration of HF was made down from 110 g/L,initial concectration, to 0.5 g/L and Recovery rate of HF was 99.5%. After recovery of HF, concentration of HNO₃ and CH₃COOH is 498 g/L, 265 g/L respectively. From that mixed acid, we recovered CH₃COOH using 2 stages of fractional distillation. In first stage, CH₃COOH was distilled for separation from HNO₃. And in second stage, we recoverd refined CH₃COOH by using fractional distillation for removing a little amount of HNO₃ in CH₃COOH vapor. The concentration of recovered CH3COOH in second stage is 20% and finally recovery rate of CH₃COOH is about 87.5%.
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