Single-crystalline silicon micromirrors actuated by self-aligned vertical electrostatic combdrives with piston-motion and rotation capability

Abstract

We present micromirrors actuated by self-aligned, high aspect ratio, vertical electrostatic combdrives with multi-level electrical isolation that allows bi-directional and dual-mode (independent rotation and piston motion) operation. The fabrication process, which requires only front-side processing, is based on self-aligned deep-reactive ion etching (DRIE) of silicon-on-insulator (SOI) wafers with two device layers. The two oxide layers between the device layers provide electrode isolation and etch stops for thickness control. Self-alignment of electrostatic combs in the two device layers is accomplished by creating masking features in the upper layer that are transferred into the lower layer. The masking features are typically removed, but in some cases they remain as an integral part of the completed device. SEM pictures show perfectly aligned vertical combteeth both with and without removal of the masking features. We demonstrate micromirrors of this type with +/-9degrees of optical scanning and 7.5 mum of piston motion under static actuation. Micromirrors designed for resonant scanning have optical scan angles up to +/-25degrees at 13.5 kHz. (C) 2003 Elsevier B.V. All rights reserved.