PURPOSE:To obtain a good quality purified silicon by preventing the occurrence of stain due to the growth of an abnormal oxidation membrane thereon during storage by subjecting an etching-treated surface of silicon to an irradiation treatment by micro wave or a high-temperature drying treatment. CONSTITUTION:A rod-like or bulk polycrystal silicon or wafer-like single crystal silicon is subjected to etching treatment with a hydrofluoric acid-nitric acid based etching liquid and then immediately put in a heater capable of generating microwave (e.g. 2450MHz) having =30MHz frequency, and nealy whole surface of the etching-treated-silicon is continuously irradiated (e.g. for 20sec at 1400 watt) with a microwave reflected with a shielding plate while rotating a support on which the silicon to be irradiated is put or the etching-treated silicon is subjected to a high-temperature drying treatment (for =30min at 110 deg.C). A purified silicon free from discoloration or loss of gloss and reduced in impurities is obtained by forming a homogeneous SiO2 film by suppressing the formation of Si-H bond in the surface of silicon, generally to =50% or pref. as for as minimum.
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