It was confirmed that a new type of singularity formed on wafer surfaces during the use of a standard cleaning process. Such singularities were perceived, by laser particle counters, as small particles on the wafers. It was shown that the singularities corresponded to small shallow pits which were caused by the etching effect of the cleaning solution. The pits were suggested to originate from some type of defect in the melt-grown crystals.

J.Ryuta, E.Morita, T.Tanaka, Y.Shimanuki: Japanese Journal of Applied Physics, 1990, 29[11], L1947-9