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Dissertation
A three-dimensional device simulator for the analysis of the MOS-SOS edge parasitic transistor
Doctor of Philosophy (Ph.D.), Drexel University
1990
DOI:
https://doi.org/10.17918/00009731
Abstract
Typical MOSFET devices fabricated with the silicon-on-sapphire (SOS) process have an inherent parasitic transistor at the island edge. The effect of the parasitic transistor cannot be ignored for narrow width devices. In addition, the edge parasitic effects become more pronounced after exposure to ionizing radiation. To correctly model the effect of the parasitic transistor, a three-dimensional device simulator has been developed in this work. The code is based on a numerical solution of the semiconductor equations in three dimensions using the seven-point finite differences method. Up-to-date models for the physical parameters are employed, including new depth dependent models for the carrier mobilities and lifetimes to account for the degradation near the back interface characteristic of SOS films. The difficulties in solving the semiconductor equations for devices with floating regions are discussed. Efficient iterative solvers, preconditioned with incomplete LU factorization, are implemented to solve the large linear system of algebraic equations resulting from the 3-D discretization. A novel strategy, applicable to any MOS-SOI structure, has been developed to reduce the CPU time and memory requirements. This strategy allows calculation of full I-V device characteristics on a VAX/8800 computer, without resorting to a supercomputer or special vector/parallel machine. The model equations and the numerical solutions are validated by showing the close agreement between calculated and measured device characteristics in the subthreshold, linear, saturation, and "kink" region. The importance of 3-D simulations to calculate the I-V characteristics of narrow channel devices is shown. Radiation effects are modeled by adding distributions of charges at the silicon/insulator interfaces. The high value and variability of the radiation-induced leakage current observed in practice are explained with a simple back interface charge distribution model.
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Details
- Title
- A three-dimensional device simulator for the analysis of the MOS-SOS edge parasitic transistor
- Creators
- Rafael Rios
- Contributors
- Allen Rothwarf (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- ix, 79 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021889082304721