Enhanced SiGe/Si Selective Etching by Acetic Acid in HNA Solutions

Selective SiGe etching process is crucial for the fabrication of Gate-all-around field-effect transistors (GAAFET) and three-dimensional dynamic random access memory (3D-DRAM). A mixture of HF, HNO 3 , and CH 3 COOH (HNA solution) is the etchant traditionally used to etch Si, but can also be used to etch SiGe. The effect of adding various concentrations of CH 3 COOH to HF/HNO 3 solutions on the selective etching of SiGe over Si was investigated in this study. It was found that addition of CH 3 COOH can enhance the selective etching of SiGe over Si, while an excessive amount causes etching of Si. In addition, concentration optimization of HNA solution was conducted to further increase the etching selectivity of SiGe over Si.