SPIN-CAST PLANARIZATION OF LIQUID-CRYSTAL-ON-SILICON MICRODISPLAYS

A simplified method for planarizing liquid-crystal-on-silicon (LCOS) b ackplanes is presented. The method relies on the planarizing capabilit y of spin-cast benzocyclobutene (BCB) polymeric resin. BCB planarizati on shows a sixfold reduction in step height on the surface of a typica l LCOS backplane. Contact with the underlying pixel circuitry is made by dry etching through openings in the BCB layer. Reflective metal (87 % reflectivity) is deposited over the planarized surface and patterned to form high-aperture-ratio pixel mirrors (84%). An average resistanc e of 0.75 Ohm per via was achieved with 3.6-mu m-diameter vias in 2-mu m-thick BCB. The method and the results of this LCOS backplane planar ization and postprocessing are described. (C) 1997 Optical Society of America.