Methods for Uniform Wet Etching in Narrow Trenches and Vias

Abstract

Abstract. Advanced semiconductor technology features complicated three-dimensional nanostructures and nanoconfined spaces such as nanosheets, supervias, deep contact holes and nanocavities. Uniform wet etching of such nanoconfined spaces across different feature sizes or critical dimensions (CD) is extremely challenging. Typically, etch rate decreases with decrease in CD size. In this paper we report methods to achieve uniform wet etch rate (ER) of SiO2 across different CD sizes by mixing organic solvents in the etching solution. We also report a reversal of etch rate trend where SiO2 structure of smaller CD etches faster than a larger CD, by tuning the ratio of organic to water solvents in the etching solution. We also investigate the impact of parameters such as solvent type, wall material, surface tension and ionic strength on ER. Our data suggests, while surface tension and ionic strength show no impact, the type of wall material, surface potential and organic solvent amount in the etching solution show a strong influence on SiO2 ER. Also, zeta potential could explain most of our results but not all, suggesting that surface potential is not the only factor impacting CD dependent ER in a nanoconfined spaces.