High-accuracy post-fabrication trimming of surface acoustic wave devices by laser photochemical processing

Laser direct writing reactions for molybdenum etching and Cr/Cr2O3 cermet conductivity transformation have been developed for concurrent phase and amplitude trimming of surface acoustic wave devices on LiNbO3. The molybdenum etching reaction utilizes photolytic decomposition of Cl2 with 488 nm light as a means to achieve low process temperature and avoid substrate damage. The cermet reaction utilizes a solid-state transformation in an O2 environment to render the film highly nonattenuating to surface acoustic waves with no underlying substrate damage. These techniques have been applied to trimming of reflective array compressors and have provided order-of-magnitude improvement in phase and amplitude accuracy over devices compensated by lithographic processing.