Post-processing and assembly of reflective microdisplays

— The performance and manufacturability of reflective displays can be enhanced by planarization, post-processing, and integrated assembly. Simplified methods for planarization and assembly of liquid-crystal-on-silicon (LCOS) microdisplays using polymeric resins are presented. Spin-cast benzocyclobutene (BCB) resin shows a six-fold reduction in step height on the surface of a typical LCOS backplane, at a cost significantly less than chemical mechanical polishing. Methods for dry-etching low-resistance contacts to the underlying circuitry and depositing high-reflectivity mirrors have been developed. In addition, photo-definable BCB resin has been utilized as both a spacer and adhesive technology in miniature-display assembly. Cell-gap thicknesses of 0.9–2.4 μm with 50–100-nm cell-gap variation and bonding shear strengths of 3200 ± 460 psi have been demonstrated, leading to wafer-scale assembly of LCOS cells. The photo-BCB spacer and adhesive technology is compatible with common liquid-crystal-alignment techniques. In this paper, the methods and results of LCOS backplane planarization, post-processing, and integrated display assembly are described.

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