Enhancement of selective SiGe dissolution through facilitated surface oxidation by formation of hydroxyl radicals in peracetic acid solution

Herein, we investigate the selective oxidation and dissolution behavior of SiGe over Si using mixtures of HF, H2O2, CH3COOH, and CH3COOOH (peracetic acid, PAA). We observe a significantly higher dissolution rate for SiGe compared to Si in the PAA solution. This difference can be attributed to more rapid and vigorous oxidation of the SiGe surface compared to that of the Si surface. We introduce a novel method to further enhance the selective dissolution of SiGe by controlling the formation of hydroxyl radicals in the PAA solution. When the formation of hydroxyl radicals is enhanced, the SiGe dissolution rate and selectivity significantly increase from 212 nm/min and 111 to 793 nm/min and 225, respectively. The selective etching of the SiGe layers is also achieved on vertically stacked multilayer SiGe/Si trench structures at an etching factor of 95:1. The increase in the SiGe dissolution rate and selectivity over Si can be attributed to the effective oxidation of the SiGe surface by hydroxyl radicals without causing surface roughening in either SiGe or Si. Based on the results, we propose a mechanism for the selective oxidation and dissolution of SiGe in PAA solution, with and without the enhancement of hydroxyl radicals.