BILAYER RESIST BASED ON WET SILYLATION (CARL PROCESS) FOR E-BEAM LITHOGRAPHY

The TBMA-resist made from t-butylmethacrylate and maleic acid anhydride is a highly sensitive bilayer resist for aqueous/alcoholic silylation of the developed top resist patterns. When diphenyl-iodonium tosylate instead of the corresponding triflate salt is used as photo acid generator the resist shows a better delay time stability before the post-exposure bake (approximately 1 hour) but less sensitivity. The catalytic chain length of the ester cleavage is then only 60 at a post-exposure bake temperature of 130-degrees-C. But due to the high reactivity of the iodonium salt towards e-beam radiation the resist has sufficient sensitivity to print 0.25 mum L&S with low radiation damage (dose < 10 muC/cm2) using a variable-shaped e-beam writer. Down to 0.4 mum L&S the resist is linear and shows a vacuum stability of better than 4 hours.