Characterization of ammonium silicate residue during Polysilazane (PSZ) dry etching in NF3/H2O gas chemistry

Abstract

In high aspect ratio (HAR) structure in semiconductor devices, the removal of silicon oxide (SiO2) layer is one of the critical and difficult steps. Because, it represents a possible source of high contact resistance and a decrease in gate oxide reliability. In the present study, we have employed plasma dry etching by using NF3 and H2O mixtures to find the effect of the gas chemistry on the oxide etching. Etch rates of SiO2 were reported as a function of H2O ratio, substrate temperature, and pressure. Polysilazane oxide (PSZ) was chosen in this study. PSZ processing generates ammonium hexafluorosilicate ((NH4)2SiF6) as a by-product. Therefore, there is an optimization need for high etch rate and selectivity without by-product formation. © The Electrochemical Society.