Patent ID: 8875720

Claim:
A polycrystalline silicon washing apparatus comprising: a plurality of acid baths each of which is filled with an acid and into which polycrystalline silicon is sequentially immersed, a transporting unit that sequentially transports the polycrystalline silicon to each of the acid baths, a device that flows clean air through the polycrystalline silicon washing apparatus in the direction opposite to the transport direction of the polycrystalline silicon by the transporting unit, a temperature adjusting unit which set such that a temperature of the acid in a later acid bath in which the polycrystalline silicon is immersed later in adjacent acid baths is equal to or lower than that of a former acid bath in which the polycrystalline silicon is immersed earlier and a temperature of the acid in a last acid bath is lower than that of the acid in a first acid bath; and liquid transferring units which are provided between adjacent acid baths among the acid baths, each of which transfers the acid in the later bath of two adjacent acid baths to the former acid bath, wherein the liquid transferring units are formed by overflow passages, the overflow passage provided in the last acid bath where the polycrystalline silicon is immersed into acid lastly is disposed at a highest position, the heights of the overflow passages are sequentially lowered from the later acid bath to the former acid bath, the acid in the later acid bath of two adjacent acid baths overflows to the former acid bath, a hydrofluoric acid supply system provided to supply hydrofluoric acid to the acid baths, and a nitric acid supply system provided to supply nitric acid to the last acid bath and a second-to-last acid bath.