Analysis of Fluorocarbon Film Deposited by Highly Selective Oxide Etching

Abstract
The influence of fluorocarbon film composition on oxide etching selectivity have been studied in a CHF3/CO mixture-gas plasma, using a magnetron-enhanced reactive ion etching system. The Fluorocarbon-film deposition rate dependence on CO concentration was measured. The Sputtering rate and carbon concentration of fluorocarbon films, which were deposited under various CO concentrations, were investigated. With CO addition, the carbon concentration in the fluorocarbon film increases, and the sputtering rate of the deposited film is reduced. High carbon concentration in a deposited polymer can enhance the selectivity of etching by protecting the Si surface from ion bombardment. In addition, an adequate CO mixing can yield a high selectivity of polymer deposition on a Si surface as compared to an oxide surface, which, in turn, achieves a high selectivity in oxide etching on Si.

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