pH-controlled TMAH Etchants For Silicon Micromachining

The etching characteristics of pH-controlled tetramethyl ammonium hydroxide (TMAH) by dissolving Si or acid have been studied. TMAH with 10 and 22 wt.% at 80/spl deg/C were used as etchants, (NH/sub 4/)/sub 2/,CO/sub 3/ and (NH/sub 4/)HPO/sub 4/ were used as acid. The etching rates of Si and aluminum, the etched surface roughness and the pH were measured. In order to obtain an aluminum etching rate of 0.01/spl mu//min, pH values below 12 for 22 wt. % TMAH and 11.5 for 10 wt.% TMAH were required. Etched surface roughness of less than 5 /spl mu/m and a Si