A comprehensive quantum anisotropic transport model for holes was used to study silicon PMOS inversion layer transport under arbitrary stress. The anisotropic band structures of bulk silicon and ...silicon under field confinement as a twodimensional quantum gas are computed using the pseudopotential method and a six-band stress-dependent k.p Hamiltonian. Anisotropic scattering is included in the momentum-dependent scattering rate calculation. Mobility is obtained from the Kubo-Greenwood formula at low lateral field and from the fullband Monte Carlo simulation at high lateral field. Using these methods, a comprehensive study has been performed for both uniaxial and biaxial stresses. The results are compared with device bending data and piezoresistance data for uniaxial stress, and device data from strained Si channel on relaxed SiGe substrate devices for biaxial tensile stress. All comparisons show a very good agreement with simulation. It is found that the hole band structure is dominated by 12 "wings," where mechanical stress, as well as the vertical field under certain stress conditions, can alter the energies of the few lowest hole subbands, changing the transport effective mass, density-of-states, and scattering rates, and thus affecting the mobility
This paper summarizes the electrostatics and performance of III-V field effect transistors including thin body planar MOSFETs, 3-D tri-gate MOSFETs, and Tunneling FETs (TFETs). The electrostatics of ...the III-V devices is shown to improve from thick body planar to thin body planar and then to 3-D tri-gate. Beyond the MOSFET structures, sub-threshold slope (SS) steeper than 60 mV/decade has been demonstrated in III-V TFETs. These III-V devices, especially the 3-D tri-gate MOSFET and TFET, are viable options for future ultra low power applications.
We investigate, by numerically calculating the charge stiffness, the effects of random diagonal disorder and electron-electron interaction on the nature of the ground state in the 2D Hubbard model ...through the finite-size exact diagonalization technique. By comparing with the corresponding 1D Hubbard model results and by using heuristic arguments we conclude that it is unlikely that there is a 2D metal-insulator quantum phase transition, although the effect of interaction in some range of parameters is to substantially enhance the noninteracting charge stiffness.
Process Technology Variation Kuhn, K. J.; Giles, M. D.; Becher, D. ...
IEEE transactions on electron devices,
2011-Aug., 2011-08-00, 20110801, Letnik:
58, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Moore's law technology scaling has improved performance by five orders of magnitude in the last four decades. As advanced technologies continue the pursuit of Moore's law, a variety of challenges ...will need to be overcome. One of these challenges is the management of process variation. This paper discusses the importance of process variation in modern transistor technology, reviews front-end variation sources, presents device and circuit variation measurement techniques, including circuit and memory data from the 32-nm node, and compares recent intrinsic transistor variation performance from the literature.
We present a compact model to calculate the capacitance of undoped high-mobility low-density-of-states materials in double-gate device architecture. Analytical equations for estimating the subband ...energies, while taking the effect of wavefunction penetration into the gate oxide and the effective mass discontinuity, are presented for the first time in a compact modeling framework. The surface potential equation for a two subband system is solved, assuming Fermi-Dirac statistics, and compared to numerical Schrodinger-Poisson simulations. The importance of accurately treating the charge profile distribution is illustrated, and an analytical expression for the effective oxide thickness to model the charge centroid is developed.
We review our novel simulation approach to model the effects of applied stress and wafer orientation by mapping detailed dependencies of long channel physics onto short channel device conditions in ...Silicon NMOS and PMOS. We use kp and Monte Carlo methods to show the long channel dependencies of these effects on gate fields, doping levels, extrinsic charges, and homogeneous driving fields. Our model predicts the reduced effect of wafer orientation on short channel linear and saturation current drives due to weak gate confinement, high carrier density, high stress, and high driving field prevalent in scaled devices. This reduces NMOS (110) wafer orientation loss compared to (100), while keeping PMOS (110) gains over (100) surface orientation in current drives in 〈110〉 channels, consistent with data.
This paper discusses the historical role that SiGe has played in driving the CMOS scaling roadmap, including discussion of NMOS biaxial strain and PMOS uniaxial strain. The paper also discusses the ...potential future role that Ge or SiGe may play in CMOS scaling as a high mobility replacement for the Si channel. Challenges such as poor quality germanium oxide and the small Ge bandgap are reviewed in light of recent developments (high-k metal gate, and ultra-thin body devices) in MOSFET scaling.
Ballistic on-currents of thin-body n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) are compared across group IV (Si, Ge) and III-V (InAs, In 0.5 Ga 0.5 As, GaAs, GaSb) ...materials for different body thickness values, surface orientations, and transport directions under several idealization assumptions. Previous simulation studies have shown that, as oxide capacitance increases, typical III-V channels with (100) surface perform worse than Si in the ballistic limit due to the degraded density-of-states (DOS). In this letter, simulation results based on tight-binding band structure calculations verify a recent proposal that confined III-V n-MOSFETs with small Γ-L separations overcome the DOS bottleneck and deliver high injection velocities, boosting on-current performance. By using the quantized L-valleys, GaSb with (100) or (111) surface orientations shows the best ballistic performance, outperforming all other materials. Although GaAs (100) and InAs or In 0.5 Ga 0.5 As with any surface orientation suffer from the DOS bottleneck, GaAs (111) gives higher ballistic on -currents than Si does.
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