In this paper, the material and electrical characteristics of Nickel-Silicon-Carbon (NiSi:C) films were investigated for the first time to ascertain the compatibility of NiSi:C contacts to silicon-carbon (Si:C) source/drain stressors. The incorporation of 1 atomic percent of carbon was found to increase both the Ni2Si-to-NiSi and NiSi-to-NiSi2 transformation temperatures. Our results show that the incorporation of carbon stabilizes the interfacial and surface morphology of NiSi:C films. We speculate that the incorporated carbon segregates into the NiSi:C grain boundaries and suppresses film agglomeration and NiSi-to-NiSi2 phase transformation. X-ray diffraction analysis further revealed that the formed NiSi:C films possessed a preferred orientation. Current-voltage measurements for NiSi and NiSi:C n+/p junctions exhibit similar cumulative distribution for junction leakage indicating that carbon incorporation does not have a detrimental impact on the n+/p junction integrity. Our results suggest that NiSi:C is a suitable self-aligned contact metal silicide to n-channel MOSFETs with SiC S/D stressors in a similar manner to the way in which NiSiGe is used for p-channel MOSFETs with SiGe S/D stressors.

We incorporate an additional semiconductor heterostructure beneath the transistor channel region to increase the strain-transfer efficiency of lattice-mismatched source/drain (S/D) stressors, resulting in higher strain levels in the channel region. The additional structure is lattice-mismatched with respect to the overlying Si-channel and/or with respect to the S/D stressors. For an n-FET with Si:C S/D, a SiGe region integrated beneath the Si-channel enhances the magnitude of the tensile strain in the channel region. For a p-FET with SiGe S/D, a Si:C region beneath the Si-channel enhances the strain effect in the channel region. This additional structure beneath the transistor channel is called a strain-transfer structure (STS). Extensive numerical simulations were performed using the finite element method to explain how the new strain-transfer structure works. Profiles of the various strain components in the transistor channel were obtained. Dependence of the strain effect on geometrical features of the new transistor structure will also be reported.

We investigated the material and electrical characteristics of platinum and ytterbium silicides for potential applications as metallic Schottky-barrier source/drain (S/D) and fully-silicided (FUSI) gate electrodes in fin field-effect transistors (FinFETs). Due to the low electro-negativity parameter of ytterbium, a low temperature silicidation process was developed to avoid the reaction of ytterbium with the isolation regions (i.e. SiO2 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.

A MOSFET formed by a Si cantilever channel suspended between source/drain “anchors” wrapped all-around by high-κ dielectric and metal gate is demonstrated. The device shows excellent subthreshold characteristics and low leakage currents due to the fully depleted body and the gate-all-around architecture implemented with a high-κ dielectric and metal gate. At the same time this also allows a high drive current due to mobility enhancements arising from volume inversion of the cantilever channel such that a large ION/IOFF is achieved.

Electronic structure calculations on composite channels, consisting of indium arsenide grown on the technologically relevant (001), (011) and (112)-orientated silicon surfaces are reported. The calculations are performed with NEMO 3-D, where atoms are represented explicitly in the sp3d5s* tight-binding model. The Valence Force Field (VFF) method is employed to minimize the strain. NEMO 3-D enables the calculation of localized states in the quantum well (QW) and their dispersion in the quantum well plane. From this dispersion, the bandgap, its direct or indirect in character, and the associated effective masses of the valence and conduction band can be determined. Such composite bandstructure calculations are demonstrated here for the first time. The numerical results presented here can then be included in empirical device models to estimate device performance. Pure InAs QWs create a direct bandgap material, with a relatively small gap and effective masses of about one order of magnitude smaller than for pure Si QW of equivalent thickness. Si, on the other hand, has a larger bandgap, superior thermal and mechanical properties, and a heavily invested industry. Thus heteroepitaxy of both components is expected to yield a highly optimized overall system. For samples grown along the (001) direction, Si is a direct bandgap material, and deposition of an InAs 3nm layer reduces substantially the hole effective mass and slightly the electronic mass, decreasing the magnitude of the gap. Along the (011) and (112)-growth direction, Si QWs are indirect bandgap material, and deposition of a few InAs layers suffies to make the new material a direct-bandgap heterostructure, decreasing significantly the electronic effective mass. (011) and (112) are the experimentally most relevant growth directions since they prevent heterointerface dipoles.

Silicon (Si) source and drain (S/D) regions have been successfully integrated in thin-body silicon-germanium-on-insulator (SGOI) n-FETs. The selectively grown Si S/D induces uniaxial tensile strain in the SiGe channel. Devices with gate length LG down to 50 nm were fabricated. The Si S/D gives rise to 40% higher saturation drive current IDsat for transistors fabricated on Si0.60Ge0.40-on-insulator substrates. For n-FETs fabricated on Si0.75Ge0.25-on-insulator substrates, a 27% IDsat enhancement was observed. Lattice mismatch between the silicon S/D region and the SiGe channel was exploited to induce lateral tensile strain and vertical compressive strain in the channel, leading to enhancement in electron mobility. Analyses of contributions from the tensile strain to mobility enhancement and performance improvement are discussed