Digest of Technical Papers. 2005 Symposium on VLSI Technology, 2005.
This paper shows, for the first time, the successful introduction of recessed, strained Si0.8Ge0.... more This paper shows, for the first time, the successful introduction of recessed, strained Si0.8Ge0.2 in the source and drain regions of pMOS MuGFET devices, improving the on-state current of these devices by 25%, at a fixed off-state condition. The improvement is shown to be a combined effect of compressive stress introduced along the channel, and of a reduced series resistance.
Several device concepts have been further evaluated after the successful implementation of epitax... more Several device concepts have been further evaluated after the successful implementation of epitaxial Si, SiGe and/or Si:C layers. Most of the next device generations will put limitations on the thermal budget of the deposition processes without making concessions on the epitaxial layer quality. In this work we address the impact of ex-situ wet chemical cleans and in-situ pre-epi bake steps, which are required to obtain oxide free Si surfaces for epitaxial growth. The combination of defect measurements, Secondary Ion Mass Spectroscopy, photoluminescence, lifetime measurements, and electrical diode characterization gives a very complete overview of the performance of low-temperature pre-epi cleaning methods. Contamination at the epi/substrate interface cannot be avoided if the pre-epi bake temperature is too low. This interface contamination is traceable by the photoluminescence and lifetime measurements. It may affect device characteristics by enhanced leakage currents and eventually...
The aim of this study is to explain how a quantum network can be used as simple model to calculat... more The aim of this study is to explain how a quantum network can be used as simple model to calculate complex band structures. The paper contains an introduction, a mathematical exposure of the method, and applications to graphene, boron nitride, and polyacetylene chains. Using a quantum network is a simple, intuitive, and, yet, rather accurate way to obtain a band structure for a complex material. One focus here is to invoke physical and chemical intuition to construct the effective one-body potential along the wires of a quantum network.
Journal of Chemical Information and Modeling, 2004
After a brief discussion of the structural trends which appear with increasing number of atoms in... more After a brief discussion of the structural trends which appear with 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 π−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 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.
The low-frequency noise of pMOSFETs fabricated in epitaxial germanium-on-silicon substrates is st... more The low-frequency noise of pMOSFETs fabricated in epitaxial germanium-on-silicon substrates is studied. The gate stack consists of a TiN/TaN metal gate on top of a 1.3-nm equivalent oxide thickness HfO2/SiO2 gate dielectric bilayer. The latter is grown by chemical oxidation of a thin epitaxial silicon film deposited to passivate the germanium surface. It is shown that the spectrum is of
Field-effect transistors with metal gate and HfO 2 gate dielectric on silicon-passivated germaniu... more Field-effect transistors with metal gate and HfO 2 gate dielectric on silicon-passivated germanium substrate are studied. Capacitance-Voltage characteristics show lower gate capacitance at negative gate voltages, irrespective of the device channel polarity. Possible mechanisms for this asymmetry are discussed. Reliability of the metal/high-k gate stack on sub-micron pchannel transistors is evaluated. Time-dependent dielectric breakdown analysis indicates comparable gate-stack quality on germanium and silicon substrates.
By solution of the Bethe-Goldstone equation for the Cooper pairing problem, an approximate analyt... more 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-T c cuprates. Utilizing in addition a phenomenological link between k B T c and a characteristic energy ε c =h 2 /2m * ξ 2 , with m * the effective mass, major differences are exposed in the functional relation between k B T c and ε c for s-wave materials and for non-conventional superconductors. The relation between critical temperature and ε c thereby proposed correctly reflects the qualitative properties of heavy Fermion superconductors.
After a quite brief discussion of the quantal liquids He, He and H, 'classical' e... more After a quite brief discussion of the quantal liquids He, He 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.
High quality epitaxy at low temperatures using AP/RP-CVD requires low moisture background levels ... more 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.
We report for the first time a comprehensive comparison salicidation of the p-and n-gates by poly... more We report for the first time a comprehensive comparison salicidation of the p-and n-gates by poly etch-back for p-type devices of the intra-die matching performance of most advanced multiple [3]. MuGFETs were fabricated with a fin height Hfin of 65nm and gate (MuGFETs) and planar bulk MOSFET technologies in terms of fin widths Wfin down to 25nm using resist and hard mask trimming.
This work presents HiK/metal gate Ge MOSFET devices with a conventional layout and made in a comp... more This work presents HiK/metal gate Ge MOSFET devices with a conventional layout and made in a complete Si-like process flow. The fabricated pFET long-channel conventional devices equal the best pFET long-channel mobility results obtained elsewhere on ring-shaped devices made with simplified process flows. The hole mobility is significantly above the Si universal, with a peak mobility value of ∼250 cm 2 (V s) −1 . The fabricated nFET devices have electron mobility much lower than the Si universal, as is commonly observed. Also, deep sub-micron Ge pFET devices with gate lengths below 0.2 µm have been made. The implementation of a novel NiSi-like NiGe module is key to obtain deep sub-micron devices with not only a high-mobility channel, but also with an acceptably low series resistance. 0.19 µm deep sub-micron Ge devices with germanided source/drain regions demonstrate that the mobility enhancement observed in long-channel Ge pFETs as compared to Si HiK/metal gate pFETs can indeed result in deep sub-micron Ge devices with a higher drive.
Two recent experimental studies by Zweiback et al. and by Gobet et al. have motivated us to study... more Two recent experimental studies by Zweiback et al. and by Gobet et al. have motivated us to study the ground-state geometry and the consequent electronic structure of the singly-charged cationic hydrogen cluster H3+(H2)m for m=2,5 and 14, using at first the Hartree-Fock approximation. For the H+7 cluster the fully optimized ground-state geometry yeilds an isosceles triangle H3, with charge ~
Digest of Technical Papers. 2005 Symposium on VLSI Technology, 2005.
This paper shows, for the first time, the successful introduction of recessed, strained Si0.8Ge0.... more This paper shows, for the first time, the successful introduction of recessed, strained Si0.8Ge0.2 in the source and drain regions of pMOS MuGFET devices, improving the on-state current of these devices by 25%, at a fixed off-state condition. The improvement is shown to be a combined effect of compressive stress introduced along the channel, and of a reduced series resistance.
Several device concepts have been further evaluated after the successful implementation of epitax... more Several device concepts have been further evaluated after the successful implementation of epitaxial Si, SiGe and/or Si:C layers. Most of the next device generations will put limitations on the thermal budget of the deposition processes without making concessions on the epitaxial layer quality. In this work we address the impact of ex-situ wet chemical cleans and in-situ pre-epi bake steps, which are required to obtain oxide free Si surfaces for epitaxial growth. The combination of defect measurements, Secondary Ion Mass Spectroscopy, photoluminescence, lifetime measurements, and electrical diode characterization gives a very complete overview of the performance of low-temperature pre-epi cleaning methods. Contamination at the epi/substrate interface cannot be avoided if the pre-epi bake temperature is too low. This interface contamination is traceable by the photoluminescence and lifetime measurements. It may affect device characteristics by enhanced leakage currents and eventually...
The aim of this study is to explain how a quantum network can be used as simple model to calculat... more The aim of this study is to explain how a quantum network can be used as simple model to calculate complex band structures. The paper contains an introduction, a mathematical exposure of the method, and applications to graphene, boron nitride, and polyacetylene chains. Using a quantum network is a simple, intuitive, and, yet, rather accurate way to obtain a band structure for a complex material. One focus here is to invoke physical and chemical intuition to construct the effective one-body potential along the wires of a quantum network.
Journal of Chemical Information and Modeling, 2004
After a brief discussion of the structural trends which appear with increasing number of atoms in... more After a brief discussion of the structural trends which appear with 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 π−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 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.
The low-frequency noise of pMOSFETs fabricated in epitaxial germanium-on-silicon substrates is st... more The low-frequency noise of pMOSFETs fabricated in epitaxial germanium-on-silicon substrates is studied. The gate stack consists of a TiN/TaN metal gate on top of a 1.3-nm equivalent oxide thickness HfO2/SiO2 gate dielectric bilayer. The latter is grown by chemical oxidation of a thin epitaxial silicon film deposited to passivate the germanium surface. It is shown that the spectrum is of
Field-effect transistors with metal gate and HfO 2 gate dielectric on silicon-passivated germaniu... more Field-effect transistors with metal gate and HfO 2 gate dielectric on silicon-passivated germanium substrate are studied. Capacitance-Voltage characteristics show lower gate capacitance at negative gate voltages, irrespective of the device channel polarity. Possible mechanisms for this asymmetry are discussed. Reliability of the metal/high-k gate stack on sub-micron pchannel transistors is evaluated. Time-dependent dielectric breakdown analysis indicates comparable gate-stack quality on germanium and silicon substrates.
By solution of the Bethe-Goldstone equation for the Cooper pairing problem, an approximate analyt... more 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-T c cuprates. Utilizing in addition a phenomenological link between k B T c and a characteristic energy ε c =h 2 /2m * ξ 2 , with m * the effective mass, major differences are exposed in the functional relation between k B T c and ε c for s-wave materials and for non-conventional superconductors. The relation between critical temperature and ε c thereby proposed correctly reflects the qualitative properties of heavy Fermion superconductors.
After a quite brief discussion of the quantal liquids He, He and H, 'classical' e... more After a quite brief discussion of the quantal liquids He, He 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.
High quality epitaxy at low temperatures using AP/RP-CVD requires low moisture background levels ... more 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.
We report for the first time a comprehensive comparison salicidation of the p-and n-gates by poly... more We report for the first time a comprehensive comparison salicidation of the p-and n-gates by poly etch-back for p-type devices of the intra-die matching performance of most advanced multiple [3]. MuGFETs were fabricated with a fin height Hfin of 65nm and gate (MuGFETs) and planar bulk MOSFET technologies in terms of fin widths Wfin down to 25nm using resist and hard mask trimming.
This work presents HiK/metal gate Ge MOSFET devices with a conventional layout and made in a comp... more This work presents HiK/metal gate Ge MOSFET devices with a conventional layout and made in a complete Si-like process flow. The fabricated pFET long-channel conventional devices equal the best pFET long-channel mobility results obtained elsewhere on ring-shaped devices made with simplified process flows. The hole mobility is significantly above the Si universal, with a peak mobility value of ∼250 cm 2 (V s) −1 . The fabricated nFET devices have electron mobility much lower than the Si universal, as is commonly observed. Also, deep sub-micron Ge pFET devices with gate lengths below 0.2 µm have been made. The implementation of a novel NiSi-like NiGe module is key to obtain deep sub-micron devices with not only a high-mobility channel, but also with an acceptably low series resistance. 0.19 µm deep sub-micron Ge devices with germanided source/drain regions demonstrate that the mobility enhancement observed in long-channel Ge pFETs as compared to Si HiK/metal gate pFETs can indeed result in deep sub-micron Ge devices with a higher drive.
Two recent experimental studies by Zweiback et al. and by Gobet et al. have motivated us to study... more Two recent experimental studies by Zweiback et al. and by Gobet et al. have motivated us to study the ground-state geometry and the consequent electronic structure of the singly-charged cationic hydrogen cluster H3+(H2)m for m=2,5 and 14, using at first the Hartree-Fock approximation. For the H+7 cluster the fully optimized ground-state geometry yeilds an isosceles triangle H3, with charge ~
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Papers by Frederik E . Leys