Formation of NiGe through germanium oxide on Ge(100) substrate

Nemouchi, F. and Carron, V. and Lábár, János (2013) Formation of NiGe through germanium oxide on Ge(100) substrate. MICROELECTRONIC ENGINEERING, 107. pp. 178-183. ISSN 0167-9317

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Abstract

Germanium based devices are of interest due to their pe rformance potential. The use of germanium as source and drain requires low resistance access achieved by the forma tion of germanide (metal-germanium compound). The nickel mono-germanide (NiGe) is claimed to be the best candidate since it presents suitable electrical and thermo-kinetic qualities. However, since the germanium oxidizes instantaneously in air, we provide in this paper a study of reactions between a nanometric Ni film and a germanium (001) substrate in the presence of a native or controlled grown germanium oxide. The goal is to study the influence of the germanium oxide onto germanidation process. We report that whatever the germanium oxide types (native or grown) formation of nickel germanides can occur unlike to silica which limits metal/silicon reactions. Numerous characterizations such as XRD, TEM-EELS, SIMS and SEM lead us to propose a model. Whatever the oxide type as thick as 8nm, nickel react with GeO2 during its deposition and transforms into a continuous germanate layer allowing NiGe nucleation on Ge substrate. After heat treatment the entire Ni layer could react with Ge to form Ni rejecting the germanate NixOyGez toward the sample surface. This mean s that Ni element diffusion occurred even with germinate interlayer. We finally describe several applications for MOS device processes in which this property could be useful.

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