Photolytic decomposition of gold metallopolymer thin films by UV laser direct writing

Abstract

Spin-on films of polymeric Au mercaptoterpene can be photochemically decomposed at 257 nm by frequency-doubled Ar+ laser direct writing techniques at very fast writing speeds. Correlation of the linewidth of the written features with the laser beam power demonstrates that the laser writing process is purely photochemical, and that reciprocity is maintained over the entire range of accessible power density of up to 250 W/cm2. An exposure threshold is observed for the formation of adherent patterns which varies in a roughly logarithmic way with film thickness. After exposure, direct written features are developed by washing away unirradiated film with hexane and baking 15 min at 250 °C to remove all carbonaceous material, leaving behind essentially pure gold lines of high crystallinity and granular structure. Due to inherent limitations of the particular Au resinate used, final Au features have a maximum thickness of 500 Å. Resistivity is substantially higher than smooth Au films of comparable thickness.