Monolithic vertical combdrive actuators for adaptive optics

High aspect ratio vertical combdrive actuators are demonstrated which advance the capabilities and applications of SOI-MEMS by adding additional independent degrees of freedom of operation: both upward and downward vertical pistoning motion as well as bi-directional pure rotation. The methodology for the first time enables monolithic fabrication of isolated vertical combdrive sets in the SOI device layer, with combfinger self-alignment and pre-engagement (initial overlap). This is demonstrated in a micromirror device, which exhibits four modes of actuation: bi-directional static optical deflection from -20/spl deg/ to +19/spl deg/, and independent bi-directional pistoning motion from -7.5 /spl mu/m to +8.25 /spl mu/m. Lowest resonant frequency of the device is 1491 Hz in tilting mode and 2619 Hz in pistoning mode.