Continuous and uniform Ni͑Si,Ge͒ layers are formed on polycrystalline Si and Si 0.42 Ge 0.58 substrate films at 500°C by rapid thermal processing. The germanosilicide is identified as NiSi 0.42 Ge 0.58 , i.e., with the same Si-to-Ge ratio as in the substrate. The NiSi 0.42 Ge 0.58 layer has agglomerated at 600°C. This is accompanied by a diffusion of Ge out from the germanosilicide grains and the growth of a Ge-rich SiGe region in their close vicinity. These changes cause a slight variation in the atomic composition of Ni͑Si,Ge͒ detectable for individual grains by means of energy dispersive spectroscopy. Above 600°C, substantial outdiffusion of Ge from the Ni͑Si,Ge͒ grains occurs concurrently with the migration of the grains into the substrate film away from the surface area leaving a Ge-rich SiGe region behind. These observations can be understood with reference to calculated Ni-Si-Ge ternary phase diagrams with and without the inclusion of NiSi 2 . When Ge is present, the Ni-based self-aligned silicide process presents a robust technique with respect to device applications.

The formation of a ternary solid solution NiSi1−xGex, instead of a mixture of NiSi and NiGe, is found during solid-state interactions between Ni and various Si1−xGex films ranging from pure Si to pure Ge. The lattice parameters of the solid solution of orthorhombic structure increase linearly with Ge content (x) as: a=5.24+0.19x Å, b=3.25+0.16x Å, and c=5.68+0.15x Å. The specific resistivity increases from 17 μΩ cm for NiSi to 21 μΩ cm for NiSi0.71Ge0.29 and NiSi0.42Ge0.58. Although the Ge content rapidly drops from 30–60 to about 10 at. % in the solid solutions formed above 600 °C, the crystallographic structure remains unchanged and no NiSi2 [or Ni(Si,Ge)2] is found in the Si1−xGex samples even after annealing at 850 °C. Without Ge, the NiSi completely disappears at 750 °C. These results indicate a strong effect of the entropy of mixing in NiSi–NiGe on the nucleation of NiSi2.

Thermal exfoliation and crystallographic transformation of single-crystal metal oxides induced by He-ion implantation J. Appl. Phys. 94, 3045 (2003); 10.1063/1.1600525 Morphological and phase stability of nickel-germanosilicide on Si 1−x Ge x under thermal stress

Lateral growth of Ni silicide towards the channel region of metal-oxide-semiconductor transistors (MOSFETs) fabricated on ultrathin silicon-on-insulator (SOI) is characterized using SOI wafers with a 20-nm-thick surface Si layer. With a 10-nm-thick Ni film for silicide formation, p-channel MOSFETs displaying ordinary device characteristics with silicided p+ source/drain regions were demonstrated. No lateral growth of NiSix under gate isolation spacers was found according to electron microscopy. When the Ni film was 20 nm thick, Schottky contact source/drain MOSFETs showing typical ambipolar characteristics were obtained. A severe lateral encroachment of NiSix into the channel region leading to an increased gate leakage was revealed, while no detectable voiding at the silicide front towards the Si channel was observed.

Articles you may be interested inImpact of SiGe source/drain induced-compressive strain on low frequency noise in high-k/metal gate p-channel metal-oxide-semiconductor transistors Abstract. The low-frequency noise in buried SiGe channel pMOSFETs fabricated on ultra-thin body silicon-on-insulator (SOI) substrates is investigated. The total thickness of the Si/SiGe/Si body structure, which is fully depleted (FD), is 20 nm. The low-frequency noise properties are compared with FD SOI pMOSFETs with a 20 nm Si body. The effect of the Ni-silicide used in the Source/Drain were also studied, especially the case of Schottky-Barrier (SB) MOSFETs when the Ni-silicide is formed at the edges of the channel.