Characterization of chemically amplified resist for X-ray lithography by Fourier transform infrared spectroscopy

SU-8 resist was characterized for X-ray lithography from a plasma focus source by studying its cross-linking process using Fourier transform infrared (FT-IR) spectroscopy. The cross-linking process of the resist during post-exposure bake (PEB) was accurately monitored using the infrared absorption peaks at 862, 914, and 1128 cm− 1. Results showed that the cross-linking of SU-8 was effectively completed at the exposure dose of 2500 mJ/cm2 for resist thickness of 25 μm. Reliable processing conditions consisted of an intermediate PEB at 65 °C for 5 min, with the PEB temperature ramped up to 95 °C over 1.5 min and then followed by a final PEB at 95 °C for 5 min. Test structures with aspect ratio 20:1 were obtained.