On a simple and accurate quantum correction for Monte Carlo simulation

We investigate a quantum-correction method for Monte Carlo device simulation. The method consists of reproducing quantum mechanical density-gradient simulation by classical drift-diffusion simulation with modified effective oxide thickness and work function and using these modifications subsequently in Monte Carlo simulation. This approach is found to be highly accurate and can be used fully automatically in a technology computer-aided design (TCAD) workbench project. As an example, the methodology is applied to the Monte Carlo simulation of the on-current scaling in p- and n-type MOSFETs corresponding to a 65 nm node technology. In particular, it turns out that considering only the total threshold voltage shift still involves a significant difference to a Monte Carlo simulation based on the combined correction of oxide thickness and work function. Ultimately, this quantum correction permits to consider surface scattering as a combination of specular and diffusive scattering where the conservation of energy and parallel wave vector in the specular part takes stress-induced band structure modifications and hence the corresponding surface mobility changes on a physical basis into account.     

Beanspruchung und Schlupf beim Rollen elastischer Walzen

Zusammenfassung Die sich swischen zwei aufeinander abrollenden Walzen bei Voraussetzung eines station?ren Rollvorgangs einstellende Druck-und Schubverteilung sowie den auftretenden Schlupf kann man aus der Berühr-, der Healf- und der Gleitbedingung errechnen. Nach dem Aufstellen der Grundgleichungen werden drei Sonderf?lle behandelt, für die sich geschlossene L?sungen angeben lassen: 1. Gleiten im ganzen Berührgebiet, 2. Haften im ganzen Berührgebiet, 3. teilweises Gleiten und teilweises Haften bei Walzen ausgleichem Werkstoff. Vortrag, gehalten beim Kolloquium der Deutschen Rheologischen Gesellschaft in Verbindung mit der Deutschen Rheologischen Vercinigung vom 23. bis 25.5. 1960 in Berlin-Dahlem.     

Bücherchau

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Monte Carlo simulation and measurement of nanoscale n-MOSFETs

The output characteristics of state-of-the-art n-MOSFETs with effective channel lengths of 40 and 60 nm have been measured and compared with full-band Monte Carlo simulations. The device structures are obtained by process simulation based on comprehensive secondary ion mass spectroscopy and capacitance-voltage measurements. Good agreement between the measured output characteristics and the full-band Monte Carlo simulations is found without any fitting of parameters and the on-currents are reproduced within 4%. The analysis of the velocity profiles along the channel confirms that the on-current is determined by the drift velocity in the source side of the channel. Analytic-band Monte Carlo simulations are found to involve an overestimation of the drain current in the nonlinear regime which becomes larger for increasing drain voltage and decreasing gate length. The discrepancy originates from a higher nonlinear drift velocity and a higher overshoot peak in bulk silicon which is due to differences in the band structures above 100 meV. The comparison between analytic-band and full-band Monte Carlo simulation therefore shows that the source-side velocity in the on-state is influenced by nonlinear and quasiballistic transport.     

Non-linear shell dynamics based on a mixed variational formulation

A simple, but efficient procedure for the investigation of the geometrically non-linear dynamic behaviour of thin elastic shells which can be described sufficiently accurate by the Donnell-Marguerre-Mushtari-Vlasov theory is proposed and tested. It is based on a mixed variational formulation generalizing D'Alembert's principle. The discretization with respect to the space is performed by Euler's method and that with respect to the time by means of the central difference quotient. Due to the regular and simple structure of the governing algebraic equations wave propagation phenomena can be studied adequately. The introduction of an (artificial) damping allows the approximation of pure static problems and includes as well the branching of equilibrium. Some illustrative examples are presented.In honour of Professor H. Neuber's 80th birthday     

On the work theorems for finite and incremental elastic deformations with discontinuous fields: A unified treatment of different versions

Starting from the statical and kinematical relations in three different versions characterized by the use of Piola's, Kirchhoff's or Biot's (Jaumann's) stresses respectively and the corresponding deformation quantities a unified abstract formulation of the basic equations is given. Because of certain properties of the statical and geometrical operators various material independent work theorems follow including the (generalized and modified) principles of virtual displacements and virtual forces. For a hyperelastic body under conservative loading these are transformed into generalized variational principles and strengthened to complementary extremum principles. Finally the abstract formulation is applied to the incremental equations. The admissible functions are allowed to have relaxed continuity properties. Therefore the presented work theorems may be used as a basis for a consistent finite element approximation according to the mixed version or to the classical displacement formulation.     

Bücherschau

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Hole Transport in Orthorhombically Strained Silicon

Linear and nonlinear transport of holes in orthorhombically strained Si to be used in vertical p-MOSFETs is theoretically analyzed. Strong mobility enhancements compared to unstrained Si by up to a factor of three is found at a Ge content of 40% in the SiGe pillar. The anisotropy in the three Cartesian directions is rather small and the saturation velocity remains unchanged. The enhanced material properties make orthorhombically strained Si attractive for device applications, although the improvements are not as strong as for biaxial tensile strain.