Electrostatic aluminum micromirrors using double-pass metallization

The fabrication of aluminum spatial light modulators has so far required costly process engineering efforts. In this paper, a low-cost process approach is presented, suitable for the manufacture of electrostatic micromirror arrays. The mirrors are made from the second metallization of complementary metal oxide semiconductor (CMOS) or bipolar processes deposited in two passes. This metal2 is protected by a photoresist layer that can be patterned using the top passivation mask of the process. No additional layer deposition and layer structuring is necessary during postprocessing. The actuators are released in a simple surface micromachining postprocessing sequence based on a sacrificial aluminum and silicon dioxide etch. Our approach allows one metallization to be used for both the circuitry and the electrooptomechanical devices. Deformable mirror arrays of up to 16 × 16 pixels were fabricated. Static self-consistent electromechanical simulations using the finite-element method (FEM) toolbox SOLIDIS were performed for a theoretical analysis and optimization of the actuator devices.