Apparatus and method for washing polycrystalline silicon
Disclosed is a polycrystalline silicon washing apparatus that sequentially immerses polycrystalline silicon into a plurality of acid baths each of which is filled with an acid to wash the polycrystalline silicon. The temperatures of the acids in the acid baths are set such that the temperature of the acid in a later acid bath of adjacent acid baths is equal to or lower than that of a former acid bath and the temperature of the acid in the last acid bath is lower than that of the acid in the first acid bath. Each of the acid baths is provided with a temperature adjusting unit that controls the temperature of the acid at a constant value.
1. A method for washing a polycrystalline silicon comprising:
immersing the polycrystalline silicon into a high-temperature acid bath controlled at a temperature in a range of 38 to 41° C. among a plurality of acid baths to remove impurities from a surface of the polycrystalline silicon;
bringing out the polycrystalline silicon from the high-temperature acid bath; and
immersing the polycrystalline silicon into an acid bath whose temperature is 10 to 15° C. lower than that of the high-temperature acid bath to remove spots from the surface of the polycrystalline silicon.
2. The method for washing a polycrystalline silicon according to claim 1 , wherein among the plurality of acid baths, acid in one acid bath overflows into another acid bath in which the polycrystalline silicon was immersed previously.
3. The method for washing a polycrystalline silicon according to claim 1 , further comprising flowing clean air to prevent formation of oxide film on the surface of the polycrystalline silicon.
4. The method for washing a polycrystalline silicon according to claim 1 , wherein a temperature of each acid bath is controlled by a temperature adjusting unit.