Etching of tantalum in fluorine-containing high density plasmas

Abstract

Dry etching of tantalum in fluorine-containing high density plasmas has been studied. Tantalum etching as a function of gas composition of CF4/CHF3/O2 mixture and SF6/O2 mixture, inductive power, bias power, and pressure has been examined using the response surface method. The etched Ta surface was also characterized by electron spectroscopy for chemical analysis to understand the etching mechanism. Tantalum was found to be etched faster in the SF6 discharge because of the abundance of fluorine-containing active species and the absence of fluorocarbon deposition on the surface. For both CF4/CHF3/O2 and SF6/O2 mixtures, the etch rate was found to decrease with increasing pressure. The effects of CHF3, CF4, and O2 on Ta etching were found to be interactive. The dependence of Ta etching on the gas composition, inductive power, bias power, and pressure is discussed in light of the existing knowledge of plasma etching.