PURPOSE: To obtain high purity semiconductor foils useful in solar energy cells by treating an impure semiconductor foil with a reactive gas in a cristallizing state of the foil.
CONSTITUTION: Reactive gases (e.g. 20 volume% oxygen and 80 volume% argon) are led through cristal frit of about 1 cm arranged on a substrate in a solid/ liquid phase boundary. The frit is extended over the whole width of a silicon foil, the reflux ratio of the gases is about 5m3/hour and a temperature around a gas treating zone is about 1410°C close to a two-phase balancing temperature. A large amount of carbon impurity, boron and phosphorus is reduced by the treatment. After cooling, the silicon foil is treated with acid or alkali (e.g. 20% sodium hydroxide at 70° for 10 min) to purify its surface and metallic impurities such as chrome and titanium are removed thereby.
HORUSUTO RANGE
INGO SHIYUBIRUTORITSUHI
KARUSUTEN BAMUBATSUHA
