Prospects for Reactive Deposition of Custom Index Optical Films by Pulsed Sputtering

D. J. Christie & D. C. Carter, Advanced Energy Industries Inc.
W. D. Sproul, Reactive Sputtering Consulting, LLC

Films with customized index of refraction can be deposited by reactive sputtering. New coatings can be created by the optical coating designer with these options. Two possible techniques are reactive co-sputtering and two gas reactive sputtering. In reactive co-sputtering, two adjacent targets are sputtered so material from each target, and reactive gas, impinge on the work piece, making a compound on its surface. Two gas reactive sputtering uses a single target material and a mixture of reactive gases. The system of the target material and the reactive gases is chosen such that both compounds are optically clear, but with different indexes of refraction. By varying the relative mix of the gases, and hence the composition of the resulting compound, the index of refraction can be varied. Modeling of both approaches clearly shows that access to the entire control space can be accomplished only with partial pressure regulation of the reactive gases. Hence, partial pressure measurement and regulation of the reactive gas are enabling technologies for both approaches. The characteristics and relative merits of the co-sputtering and two gas reactive sputtering approaches are reviewed. Modeling and experimental results for two gas reactive sputtering of customized index optical films are presented.

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The Authors

David Christie Advanced Energy Industries, Inc. David Christie is a Senior Scientist at Advanced Energy, where he has been employed since 1995. His work is focused on power conversion for plasma processes. His research interests include pulsed powe... Read more