Poly(t-BOC-styrene sulfone)-Based Chemically Amplified Resists for Deep-UV Lithography.

The unique ability of the tert-butyloxycarbonyl protecting group (t-BOC) to be removed by a catalytic amount of strong acid has intensified the search towards new chemically amplified resist systems based on this chemistry. A series of new copolymers of t-BOC-styrene and sulfur dioxide have been prepared by free radical polymerization. These polysulfones function as chemical amplification positive resists for deep-UV lithography when mixed with either 2,6-dinitrobenzyl tosylate or triarylsulfonium salt acid precursors. The lithographic characteristics of 2:1 and 3:1 polysulfones have been evaluated. The new positive deep-UV photoresists are aqueous base developed and are capable of 0.5microns resolution. Even though the photoresists containing 2,6-dinitrobenzyl tosylate are less sensitive than the onium salt formulations, they displayed greater contrast values. For example the poly(t-BOC-styrene sulfone) (2:1) 15 wt% tosylate resist formulation exhibits a sensitivity of 26 mJ/cm sup 2 and a contrst of ~20.