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A Selective Etching Process for Chemically Inert High-k Metal Oxides

  • Katherine L. Saenger (a1), Harald F. Okorn-Schmidt (a1) and Christopher P. D'Emic (a1)

Abstract

Once annealed, high-k metal oxides such as HfO2 and Al2O3 can be extremely difficult to etch by wet chemical methods. Here we describe how ion bombardment at relatively low energy (a few hundred eV) can be used to make exposed regions of annealed HfO2 films etchable in aqueous HF-based solutions. HfO2 layers, 2–5 nm in thickness, were deposited by atomic layer chemical vapor deposition (ALCVD) on Si substrates, annealed at 700 °C, and subjected to selected-area ion bombardment supplied by an oxygen plasma in a reactive ion etching tool. Etch times (as indicated by time to “dewet“) were examined as a function of HfO2 thickness, the power and time of oxygen plasma treatments, post-oxygen-plasma anneals, and wet etch chemistry. Strategies for etching thicker films and additional data provided by electrochemical open circuit potential (OCP) measurements will also be discussed.

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1. Liu, L., Pey, K.L., and Foo, P., “HF wet etching of oxide after ion implantation,” Proceedings 1996 IEEE Hong Kong Electron Devices Meeting, 29 June 1996.
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3. Barnett, J., Riley, D., Messina, T.C., Lysaght, P., “Wet etch enhancement of HfO2 films by implant processing,” Proceedings of UCPSS Ultra Clean Processing Technology 16 September 16, 2002, Oostende, Belgium (http://ucpss.com/programme.htm).
4. Okorn-Schmidt, H.F. et al., in preparation.
5. Okorn-Schmidt, H.F., Gusev, E.P., Cartier, E., Buchanan, D.A., Rath, D.L., Callegari, A., Guha, S., Bojarczuk, N.A., Gribelyuk, M., and Copel, M., “Characterization of bulk and interface properties of dielectric layers and stacks,” in “The Physics and Chemistry of SiO2 and the Si-SiO2 Interface - 4 Massoud, H.Z. et al., Edit., Proc. Vol. 2000–2, The Electrochemical Society, Pennington, NJ, 2000).
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A Selective Etching Process for Chemically Inert High-k Metal Oxides

  • Katherine L. Saenger (a1), Harald F. Okorn-Schmidt (a1) and Christopher P. D'Emic (a1)

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