INSITU ELLIPSOMETRIC MEASUREMENTS OF X-RAY RESISTS

This paper presents the results of in situ ellipsometry of x-ray photoresists during development. PMMA was used to verify the results of previous studies and confirm the validity of the technique and the theoretical models. The technique was then applied to a negative chemically amplified photoresist Microposit XP-90104C (Shipley). Because the chemically amplified resist uses an aqueous-base developer (instead of the alcohol solvents such as in the PMMA system), in situ ellipsometry was employed to test the assumption that the resist does not swell during development. No appreciable swelling of exposed XP-90104C was observed in MF-322 developer for temperatures below 35-degrees-C. At 40-degrees-C, the onset of swelling was detected. The process of dissolution measured by ellipsometry departed slightly from a theoretical model of uniform film dissolution with an abrupt resist-developer interface. Scanning electron microscopy (SEM) images of 0.3-mu-m lines printed with XP-90104C indicate that surface roughening of the resist may account for the discrepancy of the experimental data from the uniform dissolution model.