Continuous-tone gray-scale photomask for deep-UV lithography applications

Continuous tone gray scale deep UV photomask technology offers new cost effective opportunities for the mass scale production of MEMS structures, diffractive optical elements (DOEs), computer generated holograms (CGHs), and kinoform optics. A new technology for the low cost fabrication of continuous tone gray scale photomasks for deep UV photolithography applications has been demonstrated. This technology is based on the use of a photosensitive spin-on-glass (SOG) thin film deposited onto a UV transparent substrate such as fused silica. Light exposure, from either a lithography setup or a laser pattern generator, onto the photosensitive SOG film induces a color change from clear (UV transparent) to dark (UV absorbing). The amount of photo induced color attenuation on the film is directly proportional to the energy exposure of the light, hence allowing the formation of fully continuous tone patterns. Once exposed the image pattern, with a resolution of 0.1 micrometers, is permanently fixed by heat treatment without the need of an etching step.