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The lithographic performance of chemically amplified positive resists depends on controlling the delay time between the exposure and post-exposure bake (PEB) process steps. The effect of post-exposure delay (PED) was investigated in poly(t-butoxycarbonyloxystyrene-sulfone) formulated with photoacid generators (PAG) by a variety of analytical techniques including Rutherford backscattering, infrared, X-ray photoelectron and laser ablation microprobe mass spectrometry. The results indicate that the base-insoluble residue formed during PED is primarily a surface phenomenon and is a result of incomplete deprotection at the resist surface. It was determined that ppb levels of basic vapors present in the resist processing environment affect process performance profoundly by reacting with the photogenerated acids during PED. Isolation of resist surface from the immediate environment by means of a thin, acidic, and base-soluble overcoat (covercoat) material dramatically alleviates the environmental effects by quenching basic airborne contaminants and improves PED latitude.

The X-ray and deep UV radiation response is described for resist systems consisting of poly(4-tert-butoxycarbonyloxystyrene-co-sulfur dioxide) PTBSS combined with an arylmethyl sulfone. A 2:1 4-tert-butoxycarbonyloxystyrene (TBS): sulfur dioxide (SO (sub 2)) resist has been found to function as a highly sensitive, 1.4 nm X-ray, single-component, chemically amplified resist. The same resist, however, exhibits reduced sensitivity to 0.8 nm X-rays and deep UV (248 nm) radiation. Improvement in 0.8 nm X-ray sensitivity is achieved by the addition of 12 mol% bis(3,4-dichlorobenzyl) sulfone (DCBS) to the 2:1 TBS:SO (sub 2) resist. For this two-component resist formulation, the 0.8 nm X-ray sensitive improved from > 375 to 125 mJ/cm squared. Similarly, the sensitivity of the 3:1 TBS:SO (sub 2) copolymer to deep UV radiation improves to 40 mJ/cm squared with addition of 10 mol% DCBS. Sulfones, such as DCBS, provide two-component resist formulations capable of < 0.5 micro-m resolution.

Methodology was developed for the synthesis of novel 2-substituted o-nitrobenzyl chromophores, which were derivatized as the tosylate esters. The thermal stabilities of these new tosylates fell within the range predicted from an empirical model. Lithographic sensitivities of deep UV resists made from these new esters and poly(4-(tert-butoxycarbonyloxy)styrene-sulfone) ranged from 45 to 90 mJ/cm squared.