Mass spectroscopic and degassing characteristics of polymeric materials for 157 nm photolithography

We report on the mass spectroscopic and the degassing characteristics of an epoxy novolac-based chemically amplified photoresist, with triphenylsulfonium hexafluoroantimonate as photoacid generator, using an F-2 pulsed discharge molecular laser at 157 nm. This photoresist has been used previously for optical (248 nm), e-beam, and X-ray microlithography both in wet and dry development processes. For laser energy of 1 mJ per pulse focused on the sample and 5 MW/cm(2) intensity, photofragments with m/e less than 40 amu have a higher probability of formation. These fragments are mainly attributed to the breaking of the substituents of the aromatic rings. The specific fragments observed are: H, H-2, C, CH, CH2, CH3, O, OH, H2O HF,C-2,C2H,C2H2, C2H3, CO, C2H4, C2H5, C2H6, H2CO OCH3, O-2, C3H3, C3H4, C3H5, C3H6, C3H7, C2H3O, C3H8, C2H5O, C3O, C3HO, C3H2O, C3H3O, C3H4O, C3H5O, C2HO2, C2H2O2, C2H3O2, C2H4O2, C2H5O2 and C2H6O2. Comparison of these results with the ones obtained from samples with pure epoxy novolac polymer show that the direct fragmentation of the side polymer bonds is predominant over bond breaking arising from the presence of the triphenylsulfonium salt sensitizer.