Nickel-based contact metallization for SiGe MOSFETs: progress and challenges
The Ni-based self-aligned silicide process has attracted a rapidly growing interest for contact metallization in Si technology, as the device dimensions are scaled down into the sub-100 nm regime. Incorporation of Ge in the electrodes of a MOSFET, i.e. gate and source/drain, in order to further enhance device performance, has made the study of NiSi1?xGex interactions a scientifically and technologically important issue. Among the different germanosilicides of Ni, NiSi1?uGeu (i.e. mono-germanosilicide, with u possibly different from x in the Si1?xGex) is the most desirable phase due to its low specific resistivity of 1225 ??cm. The focus of the present work is placed on issues concerning the phase and morphology stability of NiSi1?uGeu on single-crystal and polycrystalline Si1?xGex substrates. The related experimental data from our recent work are analysed with reference to two classics on the formation of silicides by dHeurle [J. Mater. Res. 3 (1988) 167] and by dHeurle and Gas [J. Mater. Res. 1 (1986) 205]. Influences of C and Pt on the stability of NiSi1?uGeu are also covered. The electrical properties of the NiSi1?uGeuSi1?xGex contact are discussed referring to our latest experimental results.
contact silicide resistivity nickel silicon-germanium interface surface morphology