The full silicidation of silicon gate electrodes using Ni-Tb alloy was investigated for metal oxide semiconductor field effect transistor ͑MOSFET͒ applications. Results showed that a dual-layer silicide gate consisting of a top NiTb silicide layer and a bottom NiSi layer was formed. Full silicidation using Ni 0.8 Tb 0.2 resulted in a gate work function of 4.41 eV. This is lower than a work function of 4.68 eV obtained from full Ni silicidation. The work function lowering was linked to structural changes in the underlying NiSi layer. No physical or electrical degradation was observed after forming gas annealing at 420°C for 30 min. NiTb-silicided gate electrodes have work functions suitable for application in advanced transistor structures.Due to aggressive scaling of complementary metal-oxidesemiconductor ͑CMOS͒ devices, metal gates electrodes are required for replacing conventional poly-Si gates to overcome polydepletion and dopant penetration problems. 1 However, in selecting suitable metal gate materials, their work functions must be considered to control the transistor's threshold voltage ͑V TH ͒. 2,3 To obtain low and symmetrical V TH for optimal device performance, the gate work function must be close to the conduction and valence bands for nand p-channel bulk CMOS transistors, respectively, or about 0.2 eV above and below the intrinsic Si Fermi level for advanced transistor structures ͑surround-gate or double-gate transistors͒. 2 In recent years, fully-silicided ͑FUSI͒ NiSi has become an attractive metal electrode candidate because of its compatibility with the current CMOS process and its tunable work function. 4-8 It was demonstrated that a wide work function range ͑4.29-4.99 eV͒ for NiSi can be obtained by the total silicidation of doped poly-Si gates using various dopants ͑e.g., As, P, and B͒. 8 Alternatively, the formation of a FUSI ternary silicide with Ni and a second metal is another attractive work function tuning method. For example, Co x Ni 1−x Si 2 was reported by Sim and co-workers to show a linear work function tunability from the intrinsic Si Fermi level to ϳ0.2 eV above it. 9 In addition, it was also proven that by incorporating a large concentration of Pt ͑ϳ33%͒ into a ternary silicide with Ni, a suitable p-MOS metal gate work function can be obtained. 10 Still, the prospect of forming ternary silicides using a Ni-rare earth metal alloy for lower work function modulation has not been explored. Terbium ͑Tb͒, which is one of the rare-earth ͑or lanthanide͒ group of elements, has been reported to possess a low work function ͑ϳ3.0 eV͒. 11 In this study we investigated the effect of alloying Ni with Tb for FUSI metal gate applications. Experimentalp-Type Si͑100͒ substrates were used for FUSI MOS capacitor fabrication. After standard pregate cleaning, a SiO 2 gate dielectric ͑10 nm͒ was thermally grown and etched to obtain different thicknesses for work function extraction. Undoped amorphous Si ͑60 nm͒ was deposited by low-pressure chemical vapor deposition. The Si gate was then patterned and Ni ...

Dielectric and optical properties of epitaxial rare-earth scandate films and their crystallization behavior

We report the use of nickel-platinum silicide (NiPtSi) as a source/drain (S/D) material for strain engineering in P-MOSFETs to improve drive current performance. The material and electrical characteristics of NiPtSi with various Pt concentrations was investigated and compared with those of NiSi. Ni 0.95 Pt 0.05 Si was selected for device integration. A 0.18 µm gate length P-MOSFET achieved a 22% gain in I Dsat when Ni 0.95 Pt 0.05 Si S/D is employed instead of NiSi S/D. The enhancement is attributed to strain modification effects related to the nickel-platinum silicidation process.

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We investigated the material and electrical characteristics of platinum and ytterbium silicides for potential applications as metallic Schottky-barrier source/drain (S/D) and fullysilicided (FUSI) gate electrodes in fin field-effect transistors (FinFETs). Due to the low electronegativity parameter of ytterbium, a low temperature silicidation process was developed to avoid the reaction of ytterbium with the isolation regions (i.e. SiO 2 and SiN) to integrate ytterbium silicide successfully in mesa-isolated n-FinFETs. The integration of FUSI metal gate into p-FinFETs was also explored in this work and a novel two-step silicidation process that integrates simultaneously two different phases of platinum silicide with the appropriate work function values for gate electrode and source/drain application was demonstrated.Mater. Res. Soc. Symp. Proc. Vol. 995