Triphenylsulfonium trifluoromethanesulfonate

The triphenylsulfonium trifluoromethanesulfonate (Tf) photoactive acid generator affords the highest sensitivity (3-5 mJ cm-2) for all polymer systems studied. The contrast for these systems ranged between 2 and 6 and sub-micron resolution was obtained with all the materials. Resist systems using the triphenylsulfonium hexafluoroarsenate (Ar) precursor exhibited slightly lower sensitivities (16-20 mJ cm-2) while contrast values were similar, i.e., 2-6. Upon formulation with 5 wt% 2,6-dinitrobenzyl tosylate (Ts) the substituted styrenes exhibited still lower sensitivities (65-170 mJ cm2) and contrast remained in the range of 2-6. 

P(lc-a/r-S02) and 5.2 wt% of triphenylsulfonium trifluoromethanesulfonate were dissolved in propylene glycol methyl ether acetate (PM Acetate) to formulate a resist. A film spin-cast on a NaCl plate was baked at 100 °C for 60 sec, an IR spectrum of which is presented in Figure 6a. The film was exposed to 20 nJ/cm of 254 nm radiation from an Oriel illuminator and baked at 100 °C for 90 sec (Figure 6b). The strong tBOC carbonyl absorption at 1755 cm almost dis q>peared with concurrent appearance of a broad OH absorption at 3500-3000 cm in cating add-catalyzed deprotection of the tBOC group to generate free fluoroalcohol. 

Two-component resist solutions were prepared from pofymer (0.09 g), triphenylsulfonium trifluoromethanesulfonate (0.01 g), and chloroform (1 ml) as a solvent. The resist solutions were spin-coated onto silicon wafers and baked in an oven at 100 °C (at 60 °C for 3e) for 10 min. The resist films were ocposed by monochromatic light at 250 1 nm using a JASCO CRM-FA spectro-irradiator equipped with a 2 kW Xenon-Arc lamp and with a exposed energy integrator. The films were then heated at 60 °, 100 °, or 150 °C for 10 min, and the IR spectra were measured. 

Figure 6. Acid decompositions of the model compound 5 with triphenylsulfonium trifluoromethanesulfonate (10 wt%) in solid film. Exposure 250 nm. PEB 100 C for 10 min.

Triphenylsulfonium hecafluoroantimonate and trifluoromethanesulfonate (triflate) employed as deep UV acid generators in our formulations were synthesized according to the literature 17, 18). Propylene glycol monomethyl ether acetate and cyclohexanone were used as our casting solvents. 

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