Highly Selective Etching of SiGe to Si for GAAFET

Highly selective etching of SiGe over Si is required for the fabrication of gate-all-around field-effect transistors (GAAFET). A solution consisting of a mixture of H 2 O 2 , CH 3 COOH, and HF is known to etch SiGe with high selectivity over Si. The detailed etching mechanism of SiGe and Si in this solution was investigated in this study. The effect of each chemical species on the etching of SiGe and Si was investigated using various concentrations of H 2 O 2 , CH 3 COOH, and HF. It was found that the etching rate of SiGe was highly relevant to the concentration of peracetic acid (PAA) which was produced by the reaction between H 2 O 2 and CH 3 COOH. In addition, various additives which can further increase the SiGe selectivity and their mechanisms were investigated.