This paper describes the anisotropic etching characteristics of single-crystal Si in tetramethylammonium
hydroxide (TMAH) : isopropyl alcohol (IPA) : pyrazine solutions. With the addition of
IPA to the TMAH solution, an improvement in the flatness on the etching front and a reduction
in undercutting were observed, but the etch rate on (100) Si was decreased. However, the (100) Si
etch rate was improved by the addition of pyrazine. An etch rate of 0.8 µm/min on (100) Si, which
was faster by 13 % than the etch rate for a 20-wt.% solution of pure TMAH, was obtained using
20-wt.% TMAH : 0.005-g/ml pyrazine solutions, but the etch rate on (100) Si was decreased when
more pyrazine was added to the solution. With the addition of pyrazine to a 25-wt.% TMAH solution,
no significant variations in flatness on the etching front were observed, and the undercutting
ratio was reduced by 30 ∼ 50 %. These results indicate that anisotropic etching of Si using TMAH :
IPA : pyrazine solutions provides a powerful and versatile method for realizing of intelligent microelectro-mechanical
systems (MEMS) integrated with signal-processing and compensation circuits