Boron Etch-stop In TMAH Solutions

Etch rates of <100> single crystal silicon in tetramethyl ammonium hydroxide (TMAH) solutions have been measured as a function of boron doping concentration with the purpose of studying the feasability of an etch stop. The boron concentration has been varied up to approximatly 4x10/sup 20/ cm/sup -3/. An etch ratio of 1:40 between the high and low boron concentration respectively has been obtained. This ratio may depend slightly on the temperature of the etch, but no significant variation with etchant concentration has been observed for TMAH concentrations in the range 15-45 wt%. Preliminary experiments on the effect of adding pyrazine to the etch solution indicate that pyrazine increases the etch rate slightly and seems to have the effect of reducing surface roughness.