Selective Etching of Hydrogenated Amorphous Silicon by Hydrogen Plasma

The selective etching of hydrogenated amorphous silicon (a-Si:H) with respect to crystalline Si (c-Si) by hydrogen plasma is investigated. We have revealed that a-Si:H is etched ten times faster than c-Si. With lower etching temperature, etching selectivity and etching rate of a-Si:H and c-Si increase. Under the high-pressure condition, the etch rate becomes low because the bright region of a very-high-frequency plasma moves away from the grounded electrode. The etching rate of a-Si:H is not sensitive to the structure of the a-Si:H deposited at 70–300° C. The surface morphologies of etched a-Si:H and c-Si are rougher for higher etching temperature. The mechanism of selectivity in etching is discussed.