This paper describes a new discretization scheme for quantum confinement transport simulations using a quantum drift-diffusion model. A high-resolution scheme is constructed by developing an exponential-fitting method with the slope limiter in a class of conservative schemes to simulate the flow of electrons with quantum confinement effects in MOSFETs. This method is reinterpreted as a flux-limiter method that hybridizes a low-order flux and a high-order flux into a single numerical flux. The discretization method provides good approximations to the density profile in the smooth regions and boundary layers of the electron flow and allows high-resolution simulations of quantum confinement transport in ultrasmall MOSFETs

This paper describes a new approach to construct a multidimensional discretization scheme of quantum drift-diffusion (QDD) model (or density gradient model) arising in MOSFET structures. The discretization is performed for the stationary QDD equations replaced by an equivalent form, employing an exponential transformation of variables. A multidimensional discretization scheme is constructed by making use of an exponential-fitting method in a class of conservative difference schemes, applying the finite-volume method, which leads to a consistent generalization of the Scharfetter-Gummel expression to the nonlinear Sturm-Liouville type equation. The discretization method is evaluated in a variety of MOSFET structures, including a double-gate MOSFET with thin body layer. The discretization method provides numerical stability and accuracy for carrier transport simulations with quantum confinement effects in ultrasmall MOSFET structures.

This paper presents a new parallel algorithm and performance results of iterative solution methods for three-dimensional MOSFET simulation with Gummel's method. A splitting-up operator method is proposed for incomplete factorization of sparse matrices arising from semiconductor device equations, suitable for parallel computations. This method is combined with the conjugate gradients and BiCGSTAB procedure to obtain a new parallel version of the iterative solution methods. Natural parallelism is realized by developing the solution method according to the natural ordering. In large-scale simulations of greater than 100000 grid nodes, the high parallel efficiency level over 90% can be achieved using a new-type massively parallel computer: ADENART with up to 256 processors. The real performance of the solution methods is superior to those calculated by the vectorized version of the ICCG and ILUBiCGSTAB methods using a vector-type supercomputer.>

The authors describe a three-dimensional CAD model for submicrometer MOSFETs. The model has been implemented in a three-dimensional process/device integrated simulator, SMART-II, using a supercomputer. The MOS device model for hot electron transport is based on a modified current relation including an electron temperature effect in an inhomogeneous field. The need for an improved mobility model in an inversion layer and an impact ionization model using the recent experimental data for the mean free path is discussed with emphasis on the numerical simulation for I/V characteristics of small-geometry MOSFETs from the threshold regime to the avalanche regime. It is found that this approach is effective in realizing a three-dimensional CAD model for 0.5- mu m MOSFETs. An application of the model reveals a three-dimensional effect of avalanche breakdown behavior in small-geometry MOSFETs.>

The study focuses on the numerical solution method based on a finite-difference approach with the coordinate transformation method for simulating the nonplanar oxide growth. A relaxation technique is introduced to incorporate the stress effect into oxidation kinetic equations maintaining numerical stability. In addition, for simulating the stress-dependent oxide growth, the role of the boundary condition at the free-oxide surface is discussed. The present method allows an accurate evaluation of the local stress distribution in nonplanar oxide structures and realizes the precise simulation of oxide shapes under the large stress effect. They are demonstrated in applications to both the LOCOS process with thick nitride film and the trench oxidation process, which strongly depends on the oxidation-induced stress at trench corners.>

A description is given of a three-dimensional process simulator, named SMART-P, that is based on the finite-difference approach to the supercomputer FACOM VP-100. To simulate the impurity redistribution and nonplanar structure in the Si/SiO/sub 2/ system, this simulator contains a three-dimensional oxidation model, an interaction model of impurities, a numerical model of interstitial-assisted oxidation-enhanced diffusion, and other process models. The numerical process modeling in the Si/SiO/sub 2/ system is described. The three-dimensional process modeling CAD (computer-aided design) has been realized by using efficient numerical algorithms based on the generalized coordinate transformation method. The capabilities of this simulator have been demonstrated in applications relating to both local oxidation of silicon (LOCOS) and trench-isolated 0.5 mu m MOSFET structures.>