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EP0548504A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Process for cleaning silicon mass

Assignee: Hi-Silicon Co Ltd
•
Filing: 1992-10-29
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Granted: —
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Expires: 2012-10-29
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Abstract

Abstract In a process for cleaning a silicon mass with a acid washing solution, a waste solution containing a mixed acid composed of nitric acid and hydrofluoric acid is introduced to a distillation step, and hydrofluoric acid is introduced to a distillation cooling portion to prevent precipitation of silicon dioxide. The waste cleaning liquor is distilled to recover nitric acid. In a process for cleaning a silicon mass by acid-washing with a cleaning solution containing a mixed acid composed of nitric acid and hydrofluoric acid, the cleaned silicon mass is retained in steam of high purity after acid-washing so that acid remaining on the surface of said cleaned silicon mass can be rinsed and removed with condensed water formed on the surface of said silicon mass.

Inventors

  • 👤 Hideo Ito
  • 👤 Mitsutoshi Narukawa
  • 👤 Kazuhiro Sakai

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-01 16:03
CPC Classifications
H; H10; H10P; H10P70/00; H10P70/10; H10P70/18; H10P70/12; C; C01; C01B; C01B33/00; C01B33/02; C01B33/037; H10P70/15

Claims Analysis

Total Claims: 6
Claim 1
Independent Claim 66 words
A process for cleaning a silicon mass by acid-washing with a cleaning solution containing a mixed acid composed of nitric acid and hydrofluoric acid, comprising the steps of: introducing a waste solution to a distillation step after washing with said cleaning solution; introducing hydrofluoric acid to a distillation cooling portion to prevent precipitation of silicon dioxide; and distilling said waste solution to recover said nitric acid.
Claim 2
Dependent Claim 24 words
The process as claimed in claim 1, wherein said nitric acid recovered from said waste solution is added to said cleaning solution for reuse.
Claim 3
Dependent Claim 28 words
The process as claimed in claim 1, wherein said waste solution is continuously distilled while continuously flowing a small amount of hydrofluoric acid into said distillation cooling portion.
Claim 4
Dependent Claim 59 words
The process as claimed in claim 1, wherein after said acid-washing, said waste solution is introduced to a distillation step, and said silicon mass washed is retained in steam of high purity so that acid remaining on the surface of said silicon mass can be rinsed and removed with condensed water formed on the surface of said silicon mass.
Claim 5
Dependent Claim 68 words
A process for cleaning a silicon mass by acid-washing with a cleaning solution containing a mixed acid composed of nitric acid and hydrofluoric acid, comprising the step of: retaining in steam of high purity a cleaned silicon mass after acid-washing so that acid remaining on the surface of said cleaned silicon mass can be rinsed and removed with condensed water formed on the surface of said silicon mass.
Claim 6
Dependent Claim 69 words
The process as claimed in Claim 1, wherein after said acid-washing, said washed silicon mass is subjected to a prerinsing step in which said silicon mass is immersed in purified water, then said silicon mass is retained in steam of high purity so that acid remaining on the surface of said silicon mass can be rinsed and removed with condensed water formed on the surface of said silicon mass.

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