Simulations of Modified Shallow Water Equation and Reaction Kinetics of Poly Etching on Single Wafer Process

With the downscaling of semiconductor feature size, single wafer wet etching has shown better within-wafer and wafer-to-wafer uniformity. According to previous research and analysis, liquid film thickness has a close relationship with etch loss, and numerical simulations have been applied to calculate liquid film thickness with fixed nozzle dispensing. This study investigated liquid film thickness with scanning nozzle processing and a modeled aqueous tetramethylammonium hydroxide (TMAH) poly etching method. A modified shallow water equation was used to calculate the liquid film thickness under nozzle scanning conditions. Additionally, the liquid film thickness and liquid velocity were coupled with a chemical reaction kinetic model to calculate the TMAH poly etching reaction rate on the wafer surface. Scan dispensing etch loss was calculated by integrating the reaction rate. Both the experimental and simulation results showed that the scan speed can affect within-wafer etch loss profile and that a fast scan speed could increase etch loss in wafer donut area. The simulation model could be a predictive tool for improving within-wafer etching profile.