Partial deprotection of copolymers of 4-t-butoxycarbonyloxystyrene (TBS) and sulfur dioxide (SO₂) during the process prebake step is used to improve the x-ray lithographic performance of this resist. For a 2.6:1 TBS:SO₂ single component chemically amplified resist, removal of>50 but <90% of tert-butoxycarbonyl protecting group during prebake improves the x-ray (14Å) sensitivity from a value of 50 to 15mJ/cm2. Partial deprotection during prebake is shown to minimize the film loss observed after the postexposure baking step. At 50% deprotection, the percent film loss in the exposed resist film areas is reduced from 33 to 12%. Greater percentages of resist deprotection are possible but at a consequence of reduced process control.