Characterization of iodoheptafluoropropane as a dielectric etchant. II. Wafer surface analysis

This article forms the second part of a three-part series which presents a systematic characterization of iodoheptafluoropropane (C3F7I) based oxide e tch processes in an inductively coupled high density plasma etch tool. Part s I and III of the article discuss etch process behavior and effluent compo sition, respectively. The focus of this article is on the characterization of films deposited by 1-iodoheptafluoropropane (CF2I-CF2-CF3) processes usi ng two techniques: X-ray photoelectron spectroscopy and time-of-flight seco ndary ion mass spectrometry. A significant result obtained in this study is that, while iodoheptafluoropropane has a greater tendency to polymerize th an its perfluorinated counterpart, C3F8, because of its lower F:C ratio, th e C3F7I etch process is driven, in large part, by physical mechanisms stemm ing from bombardment of the wafer surface by massive iodine ions. The mecha nisms discussed in this article provide a consistent explanation that recon ciles the highly polymerizing behavior of iodoheptafluoropropane with its r elatively low mask and stop layer selectivity, as compared to a C3F8 based process in the same inductively coupled etch tool. (C) 2001 American Vacuum Society.