Positive chemically amplified resist for deep-UV lithography

摘要

A novel approach to chemically amplified resists based on the `base cleavage' mechanism where t-boc groups serve as the imaging units and acetoxy functionalities provide solubility differential between the exposed and unexposed resist areas was realized with poly(4-acetoxystyrene-4-t-butoxycarbonyloxystyrene sulfone, PASTBSS) terpolymer based resist formulations. The acidolytic cleavage of t-boc groups occurs in both the poly(4- acetoxystyrene-4-t-butoxycarbonyloxystyrene, PASTBS) copolymer and poly(4-acetoxystyrene-4-t-butoxycarbonyloxystyrene sulfone, PASTBSS) terpolymer resist formulations but the base induced acetyl removal occurs in the solid state (in the film) only in the PASTBSS resists, indicating the need for sulfur dioxide in the polymer backbone. Not surprisingly, acetoxy groups can be removed in solution from both PASTBS and PASTBSS polymers or their t-boc deprotected analogs.