Characterization and degradation of ZEP520 resist film by TOF-PSID and NEXAFS

Degradation process of ZEP520 resist induced by chlorine atom-selective excitation was analysed in situ by photon-stimulated ion desorption (PSID) using time-of-flight (TOF) mass spectrometry. Above the chlorine K-edge, ionic products generated by main-chain scissions were observed. This observation confirms that the ZEP520 resist can achieve high sensitivity by chlorine 1s core excitation. Surface and bulk electronic structures of the ZEP520 were also probed by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy monitoring the total electron yield (TEY) and PSID, respectively. It was found that Cl+ PSID yield was strongly enhanced at the Cl 1s → σ*(Cl-C) resonance and peak positions of all ions were different from that in the TEY. This indicates that the desorbing ions observed are formed by a direct photon excitation. It was suggested that most ions are produced by photoionization of neutral precursors lacking volatile products that are generated by radiolysis on the surface