Techniques to improve the flatness of reflective micro-optical arrays

Liquid crystal over silicon is an established technology for reflective spa tial light modulators and microdisplays. In this paper, we describe progres s in improving two key performance criteria, The first is backplane flatnes s; we describe recent developments in the use of chemical mechanical polish ing to produce optically flat pixel mirrors on top of existing circuit topo graphy; we further describe the use of an assembly technique that reduces c hip bow caused by the microfabrication induced stresses in the silicon back plane. The second is liquid crystal layer thickness; we describe the use of a lithographically patterned spacer layer microfabricated on the surface o f the silicon backplane to minimize layer thickness variations. Each of the techniques produces improvements in the performance of the final device. ( C) 1999 Elsevier Science S.A. All rights reserved.