Analysis of Cross-linking Reactions for High Sensitivity and Non-antimonite Permanent Photoresist for MEMS

The permanent photoresist is a versatile material to fabricate three-dimensional structures for the Micro Electro Mechanical Systems (MEMS) field. The replacement to non-antimonite initiators is ongoing toward the mass manufacturing. We investigate on the reaction mechanism of cross-linking formulating chemically amplified negative-tone photoresists by adopting an infrared spectra measurement system. The consumption of epoxy group is monitored during post exposure bake (PEB). The patterning profile of 40 μm lines with 30 μm thickness indicates no significant difference on the photoresist formulation. However, the FT-IR measurement results and the simulation models describe the difference in cross-linking behavior in tested photoresists. The activation energy of cross-linking reaction is also calculated. The impact on cross-linking reaction from the residual solvent in photoresist film is also discussed utilizing a Thermal Desorption Spectrometer (TDS).