Techniques to improve the flatness of reflective micro-optical arrays

Abstract

Liquid crystal over silicon is an established technology for reflective spatial light modulators and microdisplays. In this paper, we describe progress in improving two key performance criteria. The first is backplane flatness; we describe recent developments in the use of chemical mechanical polishing to produce optically flat pixel mirrors on top of existing circuit topography; we further describe the use of an assembly technique that reduces chip bow caused by the microfabrication induced stresses in the silicon backplane. The second is liquid crystal layer thickness; we describe the use of a lithographically patterned spacer layer microfabricated on the surface of the silicon backplane to minimize layer thickness variations. Each of the techniques produces improvements in the performance of the final device.