Fabrication of out-of-plane curved surfaces in Si by utilizing RIE lag

This paper reports the development of a batch fabrication technology for constructing out-of-plane curved surfaces in silicon using a single masking and etching step. With the well-characterized Deep Reactive Ion Etch (DRIE) lag effect in silicon, one can create an arbitrary out-of-plane curved profile by adjusting the trench etch openings. By using trenches ranging from 2 /spl mu/m to 50 /spl mu/m wide, a smooth curved surface (1200 /spl mu/m /spl times/ 1200 /spl mu/m) with maximum depth more than 15 /spl mu/m has been fabricated. The proposed technology is especially attractive for the fabrication of electrostatic MEMS actuators. A test curved drive electrode for vertical electrostatic actuators is also fabricated.