Journal of Technology Computer Aided Design TCAD

A new Multiple Refresh technique is presented, which can be applied to the enhancement of statistics in phase space during Monte Carlo device simulation without being restricted to ergodic or stationary systems. The method allows to specify the number of particles simulated in different regions of phase space and therefore to control directly the noise in those regions. It can improve the statisti... View full abstract»

The empirical pseudopotential band-structure of Ge, Si, and GaAs is used to compute the impact ionization (pair production) rate for electrons and holes. The constant-matrix-element and Kane's random-k approximations are also employed, to assess the importance of the energy-dependence of the Coulomb matrix element, of momentum conservation, and of the joint density of states. For electrons in Si a... View full abstract»

In this paper we present a new method for the interpolation of functions using Feynman path integrals. It is argued that least-biased interpolations are obtained. The interpolation method is essentially numerical and an algorithm is given for determining the interpolation values. The core of the method is the identification of the interpolation values as expectation values of a random function. Th... View full abstract»

With shrinking device dimensions and decreasing product-development cycles, fully-automated TCAD analysis of complete semiconductor processes and devices is becoming increasingly important. We present a programmable simulation environment for VLSI technology analysis, focusing on high-level tasks including response surface modeling (RSM) and optimization. Based on process and device simulation cap... View full abstract»

An overall three-dimensional photolithography simulator is presented, which has been developed for workstation based application. The simulator consists of three modules according to the fundamental processes of photolithography, namely imaging, exposure/bleaching and development. General illumination forms are taken into account. The nonlinear bleaching reaction of the photoresist is considered a... View full abstract»

A multipurpose single-electron device and circuit simulator is presented, with which it is possible to simulate a wide variety of single-electron devices. the simulator features among others the incorporation of co-tunneling by two different simulation methods, a graphical user interface and a graphical circuit editor. A new algorithm for the simulation of very rare events, where a Monte Carlo met... View full abstract»

We introduce a combination of Delaunay methods with advancing front techniques especially suitable for local regridding and semiconductor simulation applications. element quality improvement can be handled by local mesh adaptation steps. the three-dimensional meshing algorithm is suitable for complicated structures, because of its fully unstructured nature. the resulting Delaunay mesh possesses th... View full abstract»

Level set techniques are numerical techniques for tracking moving interfaces, and have been applied to a wide collection of problems in front propagating and surface advancement. The techniques are robust, accurate, unbreakable, and extremely fast, and can be applied to highly complex two and three dimensional surface topography evolutions in etching, deposition, and photolithography, including se... View full abstract»

A criterion for the convergence of the stochastic Monte Carlo simulations is necessary to ensure the reliability of their results and to guarantee efficiency. Due to the finite scattering rate in Monte Carlo simulations all quantities are in general correlated in time. This makes the estimation of the stochastic error of the sampled statistics difficult. In this work the theoretical basis of a met... View full abstract»

The density-gradient approach to quantum transport theory is used to model the inversion layer profiles, threshold voltages and C-V characteristics of MOS capacitors with ultra-thin oxides and polysilicon gates. The results (without fitting parameters) are found to compare quite well with experimental data and with calculations made using quantum mechanics. Comparisons are also made with results o... View full abstract»

A new approach to performance metrology and qualification of digital VLSI processes with TCAD simulations is proposed. The method yields performance data on the system level directly from raw electrical device data obtained with a minimum set of device simulations. The key performance and qualification parameters are identified, pointing out the differences between these and traditional device per... View full abstract»

A computationally efficient ion implantation cumulative damage model has recently been developed and implemented in UT-MARLOWE Versions 4.0 and 4.1. Based on the modified Kinchin-Pease formula, this model accounts for damage generation and accumulation, defect encounters and amorphization in a simplified way. Good agreement with experimental impurity profiles has been obtained for As, B, BF<inf... View full abstract»

This paper presents the results of an experiment that examines the effects of standard channel formation process steps on boron channel profiles. The experiment is specifically designed to determine the role of various processing steps on reverse short channel effect (RSCE). In the experiment defect-free silicon films, uniformly doped with boron, were grown epitaxially. The samples were then subje... View full abstract»

We investigate numerical integration, preconditioning, iterative solution and multigrid strategies for a class of réaction-diffusion systems used for modeling nonequilibrium phosphorus diffusion in silicon. These problems typically yield stiff systems of equations, and their efficient numerical simulation requires the use of stable integration strategies along with fast, robust algebraic system so... View full abstract»

Halo structure is usually adopted in deep submicron MOS devices for off-state leakage current reduction. Tilt angle of the Halo implant determines dopant distribution which gives anti-punchthrough operation. In this paper, we investigate the impact of tile angle on both DC and AC performance of Halo PMOS device via 2-D simulations. For DC performance, it is found that same conduction current is ob... View full abstract»

To accurately simulate modern semiconductor process steps, a simulation tool must include a variety of physical models and numerical methods. Increasingly complex physical formulations are required to account for effects that were not important in simulating previous generations of technology. Thus flexibility in definition of models as well as numerical solving methods is highly desirable. An obj... View full abstract»

Monte Carlo ion-implant models for germanium and indium implantation into single-crystal silicon have been developed and are described in this paper. The models have been incorporated in the UT-MARLOWE ion implantation simulator, and have been developed primarily for use on engineering workstations. These models provide the required as-implanted impurity profiles as well as damage profiles, which ... View full abstract»

This paper focuses on continuous simulated annealing global optimization method to be used in conjunction with statistical response surface modeling and powerful local optimization techniques to improve the design and analysis using TCAD. View full abstract»

The reduction of computing time without loss of accuracy is a very important task for three-dimensional process simulation. We present new approaches for fast and stable simulation of etching and deposition processes by introducing non spherical structuring element algorithms to our morphological operation based cellular topography simulator. We demonstrate improvements and accelerations for a wid... View full abstract»

We present a TCAD-based approach for characterizing hot-carrier degradation in p-channel MOSFETs that includes models for hot-electron injection, carrier transport, and electron trapping in the oxide. The energy-balance equations have been solved in the silicon substrate to accurately model the carrier-heating and injection processes. This approach clearly illustrates the physical mechanisms respo... View full abstract»

Ion implantation is a critical technology in semiconductor Ultra Large Scale Integration (ULSI). Binary collision approximation (BCA)-based Monte Carlo (MC) ion implantation simulators are commonly used to predict the impurity and damage profiles. A deterministic propagator is needed in these simulators to simulate the propagation of ions in crystalline materials. A search-for-target algorithm is ... View full abstract»