TMAH etching of silicon and the interaction of etching parameters

A study of tetramethylammonium hydroxide (TMAH) etching of silicon and the interaction of etching parameters has been carried out. We find that the silicon etch rate increases as the TMAH concentration increases and it reaches a maximum at 4 wt.%. The etch rate of n-type silicon is found to be slightly higher than that of p-type silicon. We conclude that illumination has no effect on the etch rate with our present experimental set-up. Etching experiments on silicon oxide layers show that both wet and dry oxides etch faster in lower TMAH concentration, and wet oxide generally etches faster than a dry oxide layer. A higher temperature also results in a higher etch rate for both the wet and dry oxides. From factorial analysis, we conclude that for silicon etching, the interaction between TMAH concentration and substrate type is the strongest. The silicon oxide etching experiments show that temperature is the most prominent factor and the most pronounced interaction exists between temperature and TMAH concentration.