Photoresist erosion studied in an inductively coupled plasma reactor employing CHF3

The evolution of integrated circuits into the ultralarge scale integrated regime takes today’s 0.35 mm circuit design rules to even smaller values of 0.18 mm and beyond. As a consequence, photoresist masks are becoming thinner and even more prone to erosion by etching. For this work an I-line novolak resist was used. Etch rates for various process conditions using in situ ellipsometry were obtained. Also the fluorocarbon surface layer, present on top of the photoresist during steady state etching was examined with x-ray photoelectron spectroscopy. The investigated pressure range was 6 to 20 mTorr and the inductive power range was 300 to 1400 W. It was found that there are two distinct regimes of etching behavior. At inductive powers below 600 W the etching is energy flux limited, at higher inductive powers the etching is ion energy limited. © 1998 American Vacuum Society. @S0734-211X~98!07104-2#