Conor Rafferty¹, R. Kent Smith

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 151-160, 2000, DOI:10.3970/cmes.2000.001.151

Abstract The PROPHET simulator is a software system for solving partial differential equations (PDEs) in time and 1,2 or 3 space dimensions. When equipped with appropriate modules, it can be configured as a process simulator or a device simulator, with application to modeling semiconductor fabrication processes and transistor behavior. The simulator is designed with three main goals: efficiency, geometric flexibility, equation extensibility. The first two distinguish it from canned packages such as Mathematica, which do not easily allow the use of arbitrary shapes or grids and are not tuned to solve systems with 10⁵ or 10⁶ unknowns. More >

Anand L. Pardhanani¹, Graham F. Carey¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 141-150, 2000, DOI:10.3970/cmes.2000.001.141

Abstract Rapid prototyping tools that combine powerful numerics with a flexible applications interface can play a significant role in micro-scale modeling and simulation. We demonstrate this idea using the PROPHET simulator. In the first part of the investigations we extend the simulator's capability to allow analysis of carrier transport in deep submicron MOSFETs using a hydrodynamic model. The model is numerically implemented within PROPHET's dial-an-operator framework by adding certain "flux'' routines. Once implemented, the model becomes available for use in any number of spatial dimensions. We present results for MOSFET type test problems in one and More >

Selden B. Crary¹, Peter Cousseau², David Armstrong¹, David M. Woodcock³, Eva H. Mok¹, Olivier Dubochet⁴, Philippe Lerch⁴, Philippe Renaud²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 127-140, 2000, DOI:10.3970/cmes.2000.001.127

Abstract We present a new and unique software capability for finding statistical optimal designs of deterministic experiments on continuous cuboidal regions. The objective function for the design optimization is the minimization of the expected integrated mean squared error of prediction of the metamodel that will be found, subsequent to the running of the computer simulations, using the best linear unbiased predictor (BLUP). The assumed response-model function includes an unknown, stochastic term, Z. We prove that this criterion, which we name I_Z-optimality, is equivalent to I-optimality for non-deterministic experiments, in the limit of zero correlations among the Z's for More >

C.J. Wordelman, N.R. Aluru, U. Ravaioli¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 121-126, 2000, DOI:10.3970/cmes.2000.001.121

Abstract This paper describes the application of the meshless Finite Point (FP) method to the solution of the nonlinear semiconductor Poisson equation. The FP method is a true meshless method which uses a weighted least-squares fit and point collocation. The nonlinearity of the semiconductor Poisson equation is treated by Newton-Raphson iteration, and sparse matrices are employed to store the shape function and coefficient matrices. Using examples in two- and three-dimensions (2- and 3-D) for a prototypical n-channel MOSFET, the FP method demonstrates promise both as a means of mesh enhancement and for treating problems where arbitrary More >

Wenjing Ye¹, Subrata Mukherjee²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 111-120, 2000, DOI:10.3970/cmes.2000.001.111

Abstract Polynomial driving-force comb drives are designed using numerical simulation. The electrode shapes are obtained using the indirect boundary element method. Variable gap comb drives that produce combinations of linear, quadratic, and cubic driving-force profiles are synthesized. This inverse problem is solved by an optimization procedure. Sensitivity analysis is carried out by the direct differentiation approach (DDA) in order to compute design sensitivity coefficients (DSCs) of force profiles with respect to parameters that define the shapes of the fingers of a comb drive. The DSCs are then used to drive iterative optimization procedures. Designs of variable More >

K. Kaminishi¹, M. Iino², H. Bessho², M. Taneda³

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 107-110, 2000, DOI:10.3970/cmes.2000.001.107

Abstract An FEA (finite element analysis) program employing a new scheme for crack growth analysis is developed and a prediction method for crack growth life is proposed. The FEA program consists of the subroutines for the automatic element re-generation using the Delaunay Triangulation technique, the element configuration in the near-tip region being provided by a super-element, elasto-inelastic stress analyses, prediction of crack extension path and calculation of fatigue life. The FEA results show that crack extension rate and path are controlled by a maximum opening stress range, Δσ_θmax, at a small radial distance of r = d, where More >

N. Miyazaki¹, T. Tamura², K. Yamamoto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 99-106, 2000, DOI:10.3970/cmes.2000.001.099

Abstract Quantitative estimation of the failure of a gadolinium orthosilicate (Gd₂SiO₅, hereafter abbreviated as GSO) single crystal induced by thermal stress was investigated. A GSO cylindrical test specimen was heated in a silicone oil bath, then subjected to large thermal stress by room temperature silicone oil. Cracking occurred during cooling. The transient heat conduction analysis was performed to obtain temperature distribution in the test specimen at the time of cracking, using the surface temperatures measured in the test. Then the thermal stress was calculated using the temperature profile of the test specimen obtained from the heat conduction… More >

Toru Ikeda¹, Isao Arase, Yuya Ueno, Noriyuki Miyazaki

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 91-98, 2000, DOI:10.3970/cmes.2000.001.091

Abstract In electronic devices, the corners of joined dissimilar materials exist between plastic resin and a die pad or a chip. Failure of the plastic resin is often caused from these corners during the assembly process or the operation of products. The strength evaluation of the corner is important to protect the failure of plastic packages. To evaluate the singular stress field around a corner, we utilize the stress intensity factors of the asymptotic solution for a corner of joined dissimilar materials. We show that the accurate stress intensity factor can be analyzed by the displacement More >

A.N. Gulluoglu¹, C.T. Tsai²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 85-90, 2000, DOI:10.3970/cmes.2000.001.085

Abstract Twins in growing crystals are due to excessive thermal stresses induced by the temperature gradients developed during the growth process. Twinning is an important defect in advanced semiconductor crystals such as GaAS and InP. The objective of this study is to develop a computational model to predict the twin formation in the Gallium Arsenide (GaAs) crystals grown by the vertical gradient freeze method (VGF). A quantitative quasi-steady state thermal stress model is developed here for predicting the twinning formation in GaAs grown by VGF. The thermoelastic stresses in VGF grown crystal are calculated from a More >

K. Garikipati¹, V.S. Rao², M.Y. Hao³, E. Ibok⁴, I. de Wolf⁵, R. W. Dutton⁶

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 65-84, 2000, DOI:10.3970/cmes.2000.001.065

Abstract This work is based upon a careful rendering of mechanics and mathematics to describe the phenomena that influence the stress engendered by the Shallow Trench Isolation process. The diffusion-reaction problem is posed in terms of fundamental mass balance laws. Finite strain kinematics is invoked to model the large expansion of SiO₂, dielectrics are modelled as viscoelastic solids and annealing-induced density relaxation of SiO₂ is incorporated as a history-dependent process. A levelset framework is used to describe the moving Si/SiO₂ interface. Sophisticated finite element methods are employed to solve the mathematical equations posed for each phenomenon. These include More >