Migration-adsorption mechanism of metallic impurities out of chemically amplified photoresist onto silicon-based substrates

The radioactive tracer technique was applied to investigate the migration a nd adsorption behaviors of metallic impurities (i.e., Ba, Cs, Zn, and Mn) o ut of chemically amplified photoresist onto silicon-based underlying substr ates. Two important process parameters, i.e., baking temperatures and subst rate types (e.g., bare silicon, polysilicon, oxide, and nitride) were evalu ated. Our results indicated that the transition metals (Zn and Mn) have low er migration ratios than alkali metal (Cs) and alkaline earth metal (Ba), i rrespective of the substrate types and baking temperatures. The transition metals form stable complexes with the coexisting solvents and/or hydrolysis species in the photoresist layer. The size of the metal complex, the drag force in solvent evaporation, and the baking process were found to have sig nificant effects on impurity migration. A new model, together with the meta l migration in the chemically amplified photoresist and the subsequent adso rption onto the underlying substrate, was proposed to explain the pathway o f the metal migration. This model could explain the migration ratios of met allic impurities out of the photoresist layer onto the substrate surface. ( C) 2000 The Electrochemical Society. S0013-4651(00)01-026-0. All rights res erved.