Study of anisotropic etching of (100) Si with ultrasonic agitation

High precision bulk micromachining based on wet anisotropic etching of silicon is essential for the fabrication of MEMS devices. For the most commonly used KOH and tetramethylammonium hydroxide (TMAH) anisotropic etching, ultrasonic agitation has been introduced to reduce the surface roughness and improve the etching uniformity. Etching characteristics of (1 0 0) Si have been studied and compared with that using magnetic stirring and that using no agitation. Smooth pyramid-free surfaces were obtained with the uniform etching depth within the resolution of 1 mum on the same wafer being achieved at the same time. The results reveal that the ultrasonic agitation is a very efficient way to achieve smooth, defect-free silicon surface with high dimensional uniformity on the whole wafer. (C) 2002 Elsevier Science B.V. All rights reserved.