The Evaluation of Hexafluorobenzene as an Environmentally Benign Dielectric Etch Chemistry

Hexafluorobenzene was evaluated as an alternative chemistry for dielectric etch applications in a high density plasma etch chamber with reduced global warming emissions. Processes based on hexafluorobenzene exhibited global warming emissions reductions as high as 97% compared to a -based process, which is the greatest reductions level of any alternative chemistry examined to date on this tool. Using hexafluorobenzene, it is possible to operate in a regime of high etch rate and high polymerization. There are several issues, however, that need to be addressed if this chemistry is to be used for high performance dielectric etching. This material is a liquid at room temperature, which makes it difficult to deliver process gas to the chamber. In addition, this chemistry is highly polymerizing, resulting in excess polymer deposition on chamber walls leading to significant process variability for standard chamber clean times. Significantly longer chamber clean times were required between each etch to remove the excess polymer.