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A comprehensive quantum anisotropic transport model for holes is used to study silicon PMOS inversion layer transport under arbitrary stress. The results have shown that the hole band structure is dominated by 12 'wings,' where mechanical stress, as well as the vertical field under certain stress conditions, 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.

The objective of this work is to briefly illustrate the breadth of problems industrial technology computer aided design (TCAD) departments are expected to address when supporting modern semiconductor process development, focusing on two important trends. The first is the incredible expansion of the simulation domain both downward to atomic dimensions and upward to the very large-scale die-level simulations needed for product design. The second trend is the continuing necessity of using computational efficient continuum approaches, fortified with more physically rigorous methods, to meet both accuracy and wall-clock time requirements of industrial process development. Both of these trends will be illustrated with applications work done at Intel. [ABSTRACT FROM AUTHOR]

A microscopic scattering matrix method is used to examine electron transport in the collector and emitter space charge regions of silicon bipolar transistors with different base widths. Accurate drift-diffusion expressions are consistent with current and transit time simulations of the matrix process. The base distribution at the collector edge indicates that electron velocity exceeds thermal velocity in the zero-field region.

Studies of heterojunction transport, utilizing a Boltzmann equation solution, reveals that classical thermionic emission theory accurately describes the I-V property and discontinuity of the quasi-Fermi level definition at the interface. The current and quasi-Fermi level splitting agree well with bias. The distribution functions close to the heterojunction interface are non-Maxwellian.

A spectral method for solving the Boltzmann equation by the scattering matrix approach was presented. The algorithm can be used to simulate both bulk and device characteristics with arbitrary field profiles. The analysis showed thatnumerical nonorthogonal basis functions can be used for device simulation applications. However, nonorthogonal numerical basis functions do not allow the optimization of the coefficients.

A proposed method in the evaluation of the basic assumptions of macroscopic transport models is presented. Results show that the method is also applicable to more sophisticated models. Particularly, assuming temperature as scalar and drift energy as insignificant do not provide critical estimations of the device performance. Also, the estimation of an energy-dependent mobility breaks down near the channel-drain junction.

We present quantum transport simulation results for InAs and In0.7Ga0.3As double-gate MOSFETs by using an atomistic full-band basis to evaluate the tunneling currents in the OFF state. While InAs has the advantage of lower mass and higher injection velocity, it also has lower bandgap. For low gate bias, the overlap in energy of the valence band in the channel with the source/drain conduction bands results in band-to-band tunneling (BTBT) between source and drain, which clamps the OFF current. Such current can be reduced by increasing the bandgap of the material either by increasing confinement or by lowering the In content, for example, using In0.7Ga0.3As. Grading the doping of the source/drain region to create a wider barrier also reduces BTBT, but to a lesser extent. [ABSTRACT FROM PUBLISHER]

We present a core compact model for undoped, high mobility, and low density of states materials in a double gate device architecture. Analytical equations for calculating current and charge are presented in a drift-diffusion compact modeling framework. This model accurately handles both Fermi–Dirac statistics and bias-dependent diffusivity. The results from analytical equations are validated against exact numerical charge and current integrations and device simulation. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

It is well known that, in a halo-implanted metal–oxide–semiconductor field-effect transistor, the application of the drain voltage lowers the threshold voltage even in a long-channel device. This phenomenon is known as the long-channel drain-induced barrier lowering (LDIBL) or the drain-induced threshold-voltage shift (DITS). In this paper, we will investigate the physical origin of this effect and will show that the root cause has not been previously identified properly. We will identify the physical phenomenon behind the LDIBL/DITS and present an analytic model. The proposed approach is validated against both the device simulation and measurement. [ABSTRACT FROM AUTHOR]

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 two-dimensional 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. [ABSTRACT FROM AUTHOR]

Presents the scattering matrix calculation of the distribution function in semiconductor devices. Use of the technique in silicon devices exhibiting strong nonlocal effects; Simulation of a hot-electron, n-i-n diode; Convergence of the technique with the Poisson's equation.