Spatial light modulators based on micromachined reflective membranes on viscoelastic layers

Presented in this paper is a novel approach for the fabrication of low-cost integrated micromachined spatial light modulators based on electrostatic deformation of viscoelastic layers. The fabrication procedure is optimized so as to keep requirements on electronics and the mechanical layers as low as possible. In our approach, two silicon chips are bonded together with an intermediate 5 mum viscoelastic layer in between. When the bulk silicon of the top chip is etched away, a reflective surface results with very high optical quality. The top chip is coated with a 50 nm nitride layer to act as an etch stop and a 80 nm aluminum layer for reflectivity and conductivity. When alternating potentials are applied on the electrode structure, the surface deforms in a sinusoidal shape, resulting in a phase grating, as verified experimentally. Special low-stress etch holder technology was developed for back and sidewall protection of the device and its contact pads. Applications lie in the field of projection displays, optical communication networks and optical lithography. (C) 2003 Published by Elsevier B.V.