Chemically amplified resist based on the methacrylate polymer with 2-trimethylsilyl-2-propyl ester protecting group

Poly(2-trimethylsilyl-2-propyl methacrylate-co-gamma-butyrolactone-2-yl methacrylate) was synthesized and evaluated as a potential dry-developable chemically amplified photoresist. When the,counterion of the photogenerated acid does not provide a fluoride ion, e.g., sulfonate, the carbonium ion undergoes elimination to produce 2,2,3-trimethyl-2-silabut-3-ene, and regenerates another acid. The deprotection of 2-trimethylsilyl-2-propyl group of the polymer takes place in the exposed region after post-exposure bake. The difference of silicon content between the unexposed and exposed regions is large enough to form patterns using oxygen reactive-ion etching. Poly(2-trimethylsilyl-2-propyl methacrylate-co-gamma-butyrolactone-2-yl methacrylate) was evaluated as a resist for ArF excimer laser lithography. 0.24 mu m line/space patterns were obtained using the conventional developer (2.38 wt% TMAH solution) with an ArF excimer laser stepper. 1 mu m line/space patterns were obtained using dry development process with O-2 reactive ion etching.