| 摘要 |
PROBLEM TO BE SOLVED: To provide a polycrystal silicon piece having a level of cleanliness applicable to a material for producing semiconductor.SOLUTION: According to the present invention, a process liquid (a mixed acid) having a hydrofluoric acid concentration of 1-10 wt%, and a hydrogen peroxide concentration or nitric acid concentration of not greater than 2% is used, when cleaning the surface of a polycrystal silicon piece. The mixed acid having such composition is low in an etching effect since the nitric acid concentration is low. However, metal impurities to be removed form complex compounds to be efficiently removed as the liquid is composed mainly by hydrofluoric acid. When the surface of a polycrystal silicon piece is processed with such mixed acid, the yield after processing is high to give a weight loss of about 0.2-1% as the etching effect is very low. In addition, the process has such advantage that liquid agent constituents remaining on the polycrystal silicon piece are little since the acid concentration is low.SELECTED DRAWING: None |
