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Numerical Modeling of Processes and Devices for Integrated Circuits, 1994. NUPAD V., International Workshop on

Date 5-6 June 1994

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  • Proceedings of International Workshop on Numerical Modeling of processes and Devices for Integrated Circuits: NUPAD V

    Publication Year: 1994
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    Freely Available from IEEE
  • Modeling of side wall passivation and ion saturation effects on etching profiles

    Publication Year: 1994 , Page(s): 37 - 40
    Cited by:  Papers (3)
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    A novel surface kinetics model is presented for simulating silicon and polysilicon profile evolution in plasma etching processes in which low energy ions and inhibitor forming species are used. It characterizes important phenomena such as the etching of the substrate material through a thin inhibitor layer and the saturation of the etching rate with the ion flux when the etching becomes neutral starved. The simulated profiles by using this model agree very well with experiments done in an inductively coupled high density plasma source as well as in a conventional parallel plate plasma source View full abstract»

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  • Atomistic models of vacancy-mediated dopant diffusion in silicon at high doping levels

    Publication Year: 1994 , Page(s): 101 - 104
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    This paper uses Monte-Carlo simulation on the silicon lattice to investigate vacancy-mediated dopant diffusion. By considering vacancy/dopant interaction potentials which extend out to third-nearest-neighbor distances as required for pair diffusion theories, we observe the very rapid increase in dopant diffusivity at concentrations above 2×1020 cm-3 that has been observed experimentally for group IV and V atoms in silicon. We also derive an improved analytic expression for dopant diffusivity at low and moderate doping levels as a function of interaction potential that agrees with the simulation results. Further simulations verify the central role of third-nearest-neighbor interactions to vacancy-mediated diffusion in silicon View full abstract»

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  • Convergence properties of relaxation versus the surface-Newton generalized-conjugate residual algorithm for self-consistent electromechanical analysis of 3-D micro-electro-mechanical structures

    Publication Year: 1994 , Page(s): 137 - 140
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Electrostatic sensors and microactuators are typically controlled by applied voltages which create electrostatic forces that deform the structure. Therefore, accurately analyzing the performance of these sensors and actuators requires self-consistent electromechanical analysis. However, self-consistent electromechanical analysis is a difficult computational problem because the discretization grid used must track the electrostatically deformed boundaries of the structure. Self-consistent electromechanical analysis of complicated three-dimensional structures can be performed by combining a fast multipole-accelerated scheme for electrostatic analysis with a standard finite-element method for mechanical system analysis. There are two approaches for combining these analyses, one using a straight-forward relaxation scheme, and a second based on a surface-Newton method combined with a matrix-free generalized conjugate residual based solver (SNGCR). In this paper, the convergence properties of these two methods are examined. In particular, we show that relaxation will converge if the applied voltage is small enough, or if Young's modulus is large enough, but will diverge otherwise. We also show by example that although the SNGCR algorithm is guaranteed to converge only given a sufficiently close initial guess, it converges much more frequently than relaxation View full abstract»

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  • A modified simulated diffusion algorithm for global optimization of model parameters

    Publication Year: 1994 , Page(s): 89 - 91
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    The conventional optimization technique such as the gradient-based Levenberg-Marquardt (L-M) method, which has been typically used in the commercially available parameter extraction tools, can easily be trapped in the local minima of the objective function, On the contrary, a method called simulated diffusion (SD), inspired by the simulated annealing, is known to be the most effective way to find the global minimum. In this paper, the parameter extraction algorithm based on the SD, which we have modified slightly to improve the efficiency, is presented. This is the first time that “both” dc and ac model parameters of a bipolar transistor or dc model parameters of NMOS transistors in different geometry have been extracted simultaneously via the global optimization methodology using the SD View full abstract»

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  • Massively parallel device simulation using irregular grids

    Publication Year: 1994 , Page(s): 141 - 144
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    Partitioning, communication scheduling, and preconditioning algorithms are developed to implement a parallel linear solver for an irregular grid drift-diffusion device simulator. The parallel program is executed on a 64 node CM-5 and is compared with PILS running on a single processor. We obtain an average CPU time speed-up of 46.1X for each CGS iteration with no preconditioning, and a speed-up of 33.6X for the solution of the matrix View full abstract»

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  • KYOKO: a new approach to couple 2D process and device simulation

    Publication Year: 1994 , Page(s): 85 - 88
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    Coupled process and device simulation has become an important tool for reducing the cost of technology development. In this paper the 2D-process/device simulation interface KYOKO is introduced which coarsens the process simulated device structure to increase the device simulation efficiency drastically. In addition the influence of this coarsening step is evaluated for the example of an NMOS transistor View full abstract»

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  • Monte Carlo modeling of infrared multiple-quantum-well phototransistor

    Publication Year: 1994 , Page(s): 67 - 70
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    Infrared multiple-quantum-well (MQW) phototransistor is proposed and considered theoretically. The MQW phototransistor utilizes intersubband optical absorption and exhibits giant photocurrent gain which is due to the thermionic injection of hot electrons across the emitter barrier and fast electron transit through the MQW base. We use Monte Carlo simulation to study the hot electron transport effect on performance of MQW phototransistor for different base widths and electron injection energies. Transition from near ballistic hot electron transport to diffusive transport decreases the responsivity but its value can be significant in this case as well View full abstract»

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  • A more efficient approach for Monte Carlo simulation of deeply-channeled implanted profiles in single-crystal silicon

    Publication Year: 1994 , Page(s): 97 - 100
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    In this paper we report new approach for the Monte Carlo simulation of deeply-channeled implanted profiles in single-crystal silicon with greatly improved efficiency. This approach has been successfully implemented in the UT Monte Carlo code (UT-MARLOWE). A time saving of up to 212X has been observed with a 4-stage simulation. A simulation of arsenic implants with 15 keV implant energy typically takes about 12 minutes on a workstation View full abstract»

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  • Analytical calculations of a figure of merit for novel MOSFET architecture for the sub 0.25 μm range

    Publication Year: 1994 , Page(s): 11 - 14
    Cited by:  Papers (3)
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    We present a simple analytical model to evaluate the Short Channel Effect (SCE) and to compare quantitatively how different MOSFET architectures can suppress it. The resulting figure of merit will allow us to rank the structures by their SCE suppressing ability. The model itself is based on an explicit solution of the 2D Poisson equation. A discussion on this model and on the limits of the existing solutions to model the SCE is given. Choosing carefully the boundary conditions and including efficiently the junction depth results in model improvements. The model can act as a framework for a full 2D theory View full abstract»

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  • A new approach for 2-D mesh generation for complex device structures

    Publication Year: 1994 , Page(s): 159 - 162
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    Mesh generation has become one of the most important steps in technology CAD (TCAD). The ever increasing complexity of modern semiconductor devices together with certain restrictions on the grid parameters (non-obtuse angles, desirable aspect ratios, etc.) put stringent requirements on the performance of mesh generators. This paper formulates new aspects to consider in the mesh generation process View full abstract»

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  • Influence of heat flux on the accuracy of hydrodynamic models for ultra-short Si MOSFETs

    Publication Year: 1994 , Page(s): 63 - 66
    Cited by:  Papers (8)
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    The modeling accuracy of the generalized hydrodynamic model for ultra-short MOSFETs with Leff=0.1 μm is examined using a consistent Monte Carlo model as reference. It is shown that with a proper modeling of heat flux the generalized hydrodynamic model is still sufficiently accurate even for such small devices View full abstract»

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  • A Galerkin method for the arbitrary order expansion in momentum space of the Boltzmann equation using spherical harmonics

    Publication Year: 1994 , Page(s): 133 - 136
    Cited by:  Papers (2)
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    We have implemented a Galerkin method for the solution of the Boltzmann equation which allows arbitrary order spherical harmonic expansions in momentum space. The implementation of the method in one real space dimension shows the importance of including harmonics beyond first order to accurately calculate the distribution function in high field regions View full abstract»

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  • Reliable solid modeling for three-dimensional semiconductor process and device simulation

    Publication Year: 1994 , Page(s): 49 - 52
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    Since general-purpose 3D process simulators are currently not available, solid modelers greatly help the designer in building geometries for device simulators. In this contribution, a solid modeler is presented that allows reliable geometrical operations. In order to avoid numerical errors occurring at the intersection of objects built with polygons, we have chosen a data structure based on a discretization of the x-y plane of the simulation domain View full abstract»

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  • Automatic proximity correction for 0.35 μm I-line photolithography

    Publication Year: 1994 , Page(s): 92 - 94
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    Recent advances in lithography enhancement techniques such as phase shifting masks (PSM's) and off-axis illumination have raised the possibility of using I-line photolithography for 0.35μm generation ICs. It has become clear that in order to achieve the necessary line-width control, optical proximity effects must be taken into account in conjunction with these techniques. In this paper, we describe an automatic approach to optical proximity correction (OPC) that is both effective and fast. The work presented is a joint effort between SEMATECH, AT&T, and Trans Vector Technologies. To our knowledge, this is the first practical approach that can perform viable OPC on a real chip layout View full abstract»

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  • Non-ideal contacts-Schottky diode soft-breakdown and hybrid diode with contact over pn-junction

    Publication Year: 1994 , Page(s): 75 - 78
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    We applied our model of non-ideal metal-semiconductor contacts to contacts on material of various low and high dopings and on pn-junctions. Respective simulation results are presented in the paper. First, the apparent barrier lowering, which is due to tunneling, is shown as a function of doping and contact voltage drop. The soft breakdown of a Schottky diode under reverse bias is simulated. Finally we investigate how the potential in a hybrid diode is affected where the pn-junction is covered by a metal contact View full abstract»

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  • Phenomenological modeling of plasma generation for real-time control of RIE systems

    Publication Year: 1994 , Page(s): 33 - 36
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A phenomenological approach to modeling plasma parameters in a reactive ion etching system is described, combining a simplified continuum model of electrons and ions with a continuously stirred tank reactor model of plasma chemistry. The model relates equipment parameters such as power and pressure to parameters central to equipment control such as reactive radical concentration. The simplified models allow transient response characteristics of the equipment to be calculated in reasonable time View full abstract»

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  • Grid evolution for oxidation simulation using a quadtree based grid generator

    Publication Year: 1994 , Page(s): 155 - 158
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Grid and geometry movement algorithms for oxidation simulation are presented using the grid/geometry server Forest. Initial grid generation is performed using a quadtree region decimation algorithm. An oxidation solver is used to compute node velocities and the maximum time step is determined from geometry and grid considerations. The boundary nodes are then moved and geometry singularities like loop formation and region crashes are detected and removed. All the mesh nodes are moved and retriangulation is performed if necessary. The quadtree is rehashed and new triangles are allocated to conform to the new geometry. This algorithm guarantees a high grid quality at all times with minimal grid changes between time steps View full abstract»

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  • Computer-aided trade-off study of an integrated infrared sensor

    Publication Year: 1994 , Page(s): 173 - 176
    Cited by:  Papers (2)
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    We optimise the design and operation of a thermoelectric infrared radiation sensor, using the microsensor simulator SESES. Incoming radiation is in the range of 3W/m2, resulting in temperature differences of a few mK. Free convective and radiative cooling are important effects adding to bulk conduction. Our numerical system provides four essential operations required to perform the optimisation: parametrisable device geometry, a graded computational mesh through automatic mesh adaptation, an accurate mesh refinement indicator and a fast linear equation solver View full abstract»

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  • Combined asperity contact and fluid flow model for chemical-mechanical polishing

    Publication Year: 1994 , Page(s): 29 - 32
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    This paper presents, for the first time, a physical model of chemical-mechanical polishing (CMP) that combine the effects of polishing pad roughness and slurry hydrodynamic pressure. Recently, the authors introduced a statistical asperity model to analyze contact of wafer and the polishing pad. This model is extended to include slurry flow hydrodynamics. Fluid film thickness between the wafer and pad is first estimated from measured pad roughness. Fluid pressure is then calculated from finite element simulation. The model is used to investigate parametric effects of pressure, platen velocity and pad roughness View full abstract»

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  • Transient impact ionization in bulk Si [MOS devices]

    Publication Year: 1994 , Page(s): 59 - 62
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    The generation rate, Gii, due to impact ionization and the impact ionization coefficient α in bulk Si are calculated from carrier distribution functions, solving the k-space Boltzmann transport equation. Gii and α are dependent on transients, and are not universal with respect to average energy, which facts originate in the different structures in k-space distribution function even at the same average energy. In such cases, the conventional relation of αJ (where J is the current density) fails to predict Gii, so far as one takes α for the steady-state α w defined as a function of average energy View full abstract»

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  • A new scalar planewave model for high NA lithography simulations

    Publication Year: 1994 , Page(s): 45 - 48
    Cited by:  Patents (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    A high NA photolithography simulator has been developed based on the angular spectrum analysis of planewaves. Spatial partial coherence is modelled using Van Cittert-Zernike theorem, which allows the extended source in a stepper to be divided into a number of point sources. Fast Fourier transform is applied to the coherent imaging by the point sources, leading to an efficient computation of the intensities in the image space. Special attention is devoted to source discretization to avoid the intensity fluctuations and improve the speed performance. The simulator can be used to calculate the aerial images of full circuit cells in a time scale proportional to NlogN. For resist profile calculations, a new approximation method has been developed for modelling photoresist bleaching during a high NA stepper exposure. The simulator has been applied to simulation-based global proximity correction and design rule generation for IC manufacturing View full abstract»

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  • Modeling of Ti physical vapor deposition systems

    Publication Year: 1994 , Page(s): 41 - 44
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    A novel model for simulating Physical Vapor Deposition (PVD) systems is presented. The model determines profile evolution for deposition in trenches and vias by considering the major components in a PVD system. The simulator incorporates the effects of non-uniform target erosion, collimation, gas phase collisions, and particle sticking coefficients on profile evolution. Simulations for sputtered Ti are compared against experimental results View full abstract»

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  • Automatic discretization and analytical Jacobian generation for device simulation using a physical-model description language

    Publication Year: 1994 , Page(s): 147 - 150
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    This paper presents the concept of a physical-model description language, a high level modeling language far semiconductor device simulation. Two major issues in its implementation are presented with their algorithmic implementation. These are the concept of automatically assigning mesh position to device based data (automatic discretization) and the automatic generation of the analytical Jacobian by symbolic means View full abstract»

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  • Numerical modelling of non-ideal current-voltage characteristics of high-efficiency silicon solar cells

    Publication Year: 1994 , Page(s): 177 - 180
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    Under one-sun illumination, the highest energy conversion efficiencies of silicon solar cells are presently obtained with bifacially contacted n+p cells, where contact to the p-type substrate is made via small openings in the rear passivating oxide. Experimentally, it has been found that the dark and illuminated current-voltage (I-V) characteristics of these devices deviate strongly from ideal diode theory. In this work the experimental I-V curves are compared with results obtained from 2- and 3-dimensional (2D, 3D) device simulation based on experimental cell parameters. Excellent agreement between theory and experiment is obtained. The paper shows why these solar cells cannot accurately be modelled by 1D simulators and reveals the physical reasons underlying the observed non-idealities View full abstract»

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