Quantitative Analysis and Influence of CO₂ Absorbed in TMAH Solution for Silicon Etching

Abstract

This paper presents the quantitative analysis and influence of CO₂ dissolved in TMAH for silicon etching. The etching rate on the (100) plane increases at first and then decreases with the increase of CO₂ concentration. The etching rate on the (110) plane decreases monotonously with the increase of CO₂ concentration. Although the etching rate on the (110) plane is higher than that on the (100) plane at ordinary conditions, this relationship is reversed at a certain quantity of CO₂ dissolution. The etch-stop appears at higher concentration of CO₂ dissolution. It was confirmed that changes of the silicon etching characteristics are caused by concentration of carbonate anions. The CO₂ dissolution has influence on the (100) plane and no influence on the (110) plane.