The properties of epitaxial strained Si on Ge (001) grown from SiH4 at 500 °C and from Si3H8 at 350 °C have been investigated as a function of film thickness using second harmonic generation (SHG). A clear difference in the corresponding signal amplitude, for both the interface and the “bulk” contributions, is observed. After analysis of the nonlinear susceptibility tensor components, this difference is attributed to the segregation of Ge to the SiO2/Si interface. It is demonstrated that when employed in combination with more standard experimental techniques, SHG can be a valuable tool for probing and characterizing the SiO2/Si/Ge interfaces.

The impact of the Si passivation on the low-frequency noise of Ge-on-Si pMOSFETs is investigated. A transition from number to mobility fluctuations dominated 1/f noise is found going from shorter to longer channel transistors.

We report on a 65 nm Ge pFET with a record performance of Ion = 478muA/mum and Ioff,s= 37nA/mum @Vdd= -1V. These improvements are quantified and understood with respect to halo/extension implants, minimizing series resistance and gate stack engineering. A better control of Ge in-diffusion using a low-temperature epi-silicon passivation process allows achieving 1nm EOT Ge-pFET with increased performance.

DiMethylAminoGermaniumTriChloride (DiMAGeCl) is evaluated as a C-dopant source for selective SiGe and Ge epitaxy using Chemical Vapor Deposition. We determine the C-level as a function of temperature and pressure and we examine the applicability of DiMAGeCl for the growth of high quality Ge on Si.

High quality epitaxy at low temperatures using AP/RP-CVD requires low moisture background levels in the main processing gasses, as well as an excellent leak-tightness of the tool. We perform moisture measurements on two CVD production tools and link these to a comparative analysis of their performance with respect to low temperature epitaxy.

Ge selective epitaxial growth (SEG) in shallow trench isolated windows is of great interest in advanced devices due to the good lateral electrical isolation of shallow trenches and the possibility of integrating Ge on Si wafers. However, the high density of threading dislocations in strain-relaxed Ge layers and facet formation are two major concerns in Ge SEG. In this work, we have obtained facet-free growth of Ge in shallow trench isolated Si windows with a threading dislocation density (TDD) of 4.2×108 cm-2. A mass transport model is developed to simulate the Ge faceting and the factors influencing the Ge deposition selectivity are studied.

We show some results obtained in the recent years about studies performed on graphitic structured systems. These studies have been developed within a semiemprical framework and involved the use of model based on quantum networks, on embedded atoms (the March model), on sum rules and bounds and, finally, on continuum for solvation. We have obtained results on electron density, binding energies, density of states and dispersion relations, dipole polarizabilities and intermolecular forces. We have considered B and C cages, nanotubes and two-dimensional layers. More recently, we have moved the attention to the solvation of fullerene in organic solvents. We have derived an effective fullerene pair potential and we are going to extend this study by means of Monte Carlo computer simulations of liquid solutions including water as solvent for the potential interest in biochemical applications.

Germanium possesses higher electron and hole mobilities than silicon. There is a big leap, however, between these basic material parameters and implementation for high-performance microelectronics. Here we discuss some of the major issues for Ge metal oxide semiconductor field effect transistors (MOSFETs). Substrate options are overviewed. A dislocation reduction anneal >800 degrees C decreases threading dislocation densities for Ge-on-Si wafers 10-fold to 10(7) cm(-2); however, only a 2 times reduction in junction leakage is observed and no benefit is seen in on-state current. Ge wet etch rates are reported in a variety of acidic, basic, oxidizing, and organic solutions, and modifications of the RCA clean suitable for Ge are discussed. Thin, strained epi-Si is examined as a passivation of the Ge/gate dielectric interface, with an optimized thickness found at similar to 6 monolayers. Dopant species are overviewed. P and As halos are compared, with better short channel control observed for As. Area leakage currents are presented for p +/n diodes, with the n-doping level varied over the range relevant for pMOS. Germanide options are discussed, with NiGe showing the most promise. A defect mode for NiGe is reported, along with a fix involving two anneal steps. Finally, the benefit of an end-of-process H-2 anneal for device performance is shown. (C) 2008 The Electrochemical Society.

In this letter, we investigate the impact of a hybridized strain technology on the performance of FinFET-based multigate field-effect transistors (MUGFETs). The technology combines the use of supercritical strained-silicon-on-insulator (SC-SSOI) and strained contact etch stop layers (CESLs). We will show that SC-SSOI (top plane orientation ) with tensile CESL (tCESL), when used for MUGFET, leads to higher improvement in electron mobility as compared to standard SOI with tCESL. Therefore, the combination of both mobility boosters is very beneficial for n-channel MOS MUGFET. However, the impact of compressive CESL on p-channel MOS (pMOS) performance is strongly reduced and becomes even negative when used on an SC-SSOI substrate. Local strain relief of the SC-SSOI substrate is mandatory in order to achieve good pMOS device performance.

Epitaxial deposition of strained Si and SiGe to improve electron and hole mobility and Vt shift is becoming more and more part of the standard CMOS processing [1,2]. One of the most important restrictions imposed on advanced CMOS processing is that on thermal budget. For epitaxial growth processes this thermal budget is quite high. The main contribution comes however not from the growth itself, but from the in-situ H2 bake necessary to remove any oxide traces left prior to epi. Without any pre-epi etch, removal of the native oxide requires at least a bake for several minutes at 900 ̊C or higher. When combined with a wet clean which removes the native oxide and passivates the surface (usually H or Cl), this temperature can be reduced to the range of 850-750 ̊C, although this is always at the cost of a remaining C and O peak at the epi-substrate interface.

The integration of Ge channels in high performance integrated circuits requires the passivation of the (100)Ge surface prior to gate dielectric deposition. Two promising approaches are discussed here, namely: i) the deposition of an ultrathin epi-Si layer, followed by its partial oxidation prior to high-k dielectric deposition, and ii) the exposure of the Ge surface to H"2S, resulting in the formation of Ge-S bonds. The insights that can be gained by combining physico-chemical analysis of Ge surfaces and/or electrical properties of Ge-devices, with first-principles simulations are highlighted.

The initial growth mode of Si on Ge(100) was studied using SiH4 CVD under a reduced-pressure N2 ambient at 500 and 575 °C. We show that, using the appropriate conditions, 3D growth can be avoided and growth occurs in a layer-by-layer mode. To the authors' knowledge, this had up to now not been reported in literature. The critical thickness for relaxation of the Si film was found to be below 2 nm. Relaxation occurs through the formation of misfit dislocations which preserve the 2D character of the Si film. No convincing evidence for Ge up-diffusion during growth at 500 °C was found. The epitaxial growth of Ge on Ge(100) from the pyrolysis of GeH4 is also studied under H2 ambient in both the kinetic and mass-flow controlled regime. The outstanding features are discussed and some analysis is given.

Epitaxial fully strained Si films are known to form an effective passivation of the Ge(100) surface. However, we show using low-energy secondary ion mass spectrometry (SIMS) that considerable Ge surface segregation occurs for Si films grown from SiH4 at 500°C. In this study, we develop an alternative deposition process at 350°C using Si3H8 which significantly decreases the Ge peak at the Si surface. We attribute this strong reduction mainly to the fact that growth at 350°C from trisilane proceeds below the Si–H desorption temperature. Charge pumping measurements on n-type Ge devices show a reduction by approximately a factor three in the high-k/substrate interface trap density for the samples with 350°C Si passivation, compared to those using a Si passivation deposited at 500°C.

Ge pMOS mobilities up to 358 cm2/Vs are demonstrated using a Si-compatible process flow without the incorporation of strain. EOT is approximately 12 Aring with a gate leakage less than 0.01 A/cm 2 at Vt+ 0.6 V. Ge transistors are characterized with gate lengths ranging from 10 mum down to 0.125 mum, the shortest ever reported. We also present the best Ge pMOS drain current to date of 790 muA/mum at Vgt = Vd = -1.5V for an Lg of 0.19 mum

After a brief discussion of the structural trends which appear with an increasing number of atoms in B cages, a one-to one correspondence between the connectivity of B cages and C cage structures will be proposed. The electronic level spectra of both systems from Hartree-Fock calculations is given and discussed. The relation of curvature introduced into an originally planar graphitic fragment to pentagonal "defects" such as are present in buckminsterfullerene is also briefly treated. A study of the structure and electronic properties of B nanotubes will then be introduced. We start by presenting a solution of the free-electron network approach for a "model boron" planar lattice with local coordination number 6. In particular the dispersion relation E(k) for the pi-electron bands, together with the corresponding electronic Density Of States (DOS), will be exhibited. This is then used within the zone-folding scheme to obtain information about the electronic DOS of different nanotubes obtained by folding this model boron sheet. To obtain the self-consistent potential in which the valence electrons move in a nanotube, "the March model" in its original form was invoked, and the results are reported for a carbon nanotube. Finally, heterostructures, such as BN cages and fluorinated buckminsterfullerene, will be briefly treated, the new feature here being electronegativity difference.

By solution of the Bethe–Goldstone equation for the Cooper pairing problem, an approximate analytic relation is derived between coherence length ξ and the binding energy of the Cooper pair. This relation is then qualitatively confirmed by numerically solving the corresponding self-consistent gap equations, following the crossover from weak to strong coupling, in non-s-wave superconductors. The relation applies to non-conventional superconductors, and in particular to heavy Fermions and to high-Tc cuprates. Utilizing in addition a phenomenological link between kBTc and a characteristic energy εc=ℏ2/2m∗ξ2, with m∗ the effective mass, major differences are exposed in the functional relation between kBTc and εc for s-wave materials and for non-conventional superconductors. The relation between critical temperature and εc thereby proposed correctly reflects the qualitative properties of heavy Fermion superconductors.

Three areas in which Coulomb interactions are of obvious importance are considered in turn, namely liquid alkali metals, electron-hole droplets, and lithium halides. The focus in the first two areas is dominantly on critical point properties, whereas in the third area the solid-liquid transition is the predominant interest.

Relativistic virial relations are first discussed for a homogeneous electron liquid. The chemical potential is involved in such virial relations, and the approximate effects of electron correlation are studied, using the Quantum Monte Carlo (QMC) data of Kenny et al. (S.D. Kenny, G. Rajagopal, R.J. Needs, W.-K. Leung, M.J. Godfrey, AJ. Williamson and W.M.C. Foulkes (1996). Phys. Rev. Lett., 77, 1099).Attention is then shifted to inhomogeneous electron liquids. Based on Dirac's relativistic wave equation, an approximate propagator solution using a WKB-like treatment of this equation by Linderberg for central fields is a focal point. This approach, it is demonstrated here, leads back to the exact single-particle kinetic energy of the uniform electron gas and hence to the virial relations referred to above when the central field is switched off. Virial relations are then referred to for the finite central field case. Finally, a local density approximation applied to heavy atoms in intense magnetic fields is briefly treated, and another approximate virial relation is exhibited.

There is considerable current interest in the equations of state (EOS) of the two heavy metals, tantalum and plutonium. For the former, Boettger [Phys. Rev. B 64, 035103 (2001)] has recently carried out calculations based on the Dirac relativistic wave equation. Our purpose here is different, namely, it is to work with the simplest form of relativistic density-functional theory which is the relativistic Thomas-Fermi (TF) method. The predictions of this approach should come into their own at sufficiently high pressures (we work throughout at T=0) and direct contact has been made, for Ta, with the (lower-pressure) predictions of Boettger's study. Similar results for the high-pressure limiting form of the T=0 EOS for Pu are presented. Because the relativistic TF method is purely "local density" in character, the results on Ta and Pu are preceded by a full study of the relativistic homogeneous electron gas, including the relativistic exchange contribution to its EOS. An important finding there is that in the high-density limit the relativistic exchange contribution to the pressure becomes proportional to the kinetic contribution, the proportionality constant being linear in the fine-structure constant.

After a quite brief discussion of the quantal liquids He-4, He-3 and H, 'classical' elemental liquids which are treated in turn are C, P, Se and S. Phase boundaries in the (p, T) plane exist for each of these liquids, characterized by a change in local coordination number across these boundaries. Corresponding changes in other physical properties are briefly noted. Finally, following this review of elemental liquids, some liquids with two types of atom are briefly considered, the most important but also the most controversial being water.