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Title page for ETD etd-07242003-120620


Type of Document Dissertation
Author Nicklaw, Christopher J
Author's Email Address cjnicklaw@vanderbilt.edu
URN etd-07242003-120620
Title Multi-Level Modeling of Total Ionizing Dose in a-SiO2: First Principles to Circuits
Degree PhD
Department Electrical Engineering
Advisory Committee
Advisor Name Title
Ronald D. Schrimpf Committee Chair
Kenneth F. Galloway Committee Co-Chair
Daniel M. Fleetwood Committee Member
Robert Weller Committee Member
Sokrates Pantelides Committee Member
Keywords
  • ab-initio
  • defects
  • first principles
  • radiation
  • circuits
  • compact models
Date of Defense 2003-07-17
Availability unrestricted
Abstract
Oxygen vacancies have long been known to be the dominant intrinsic

defect in amorphous SiO2 . They exist, in concentrations dependent on

processing conditions, as neutral defects in thermal oxides without

usually causing any significant deleterious effects, with some spatial

and energy distribution. During irradiation they can capture holes and

become positively charged E´-centers, contributing to device

degradation. Over the years, a considerable database has been amassed

on the dynamics of E´-centers in bulk SiO2 films, and near the

interface under different irradiation and annealing

conditions. Theoretical calculations so far have revealed the basic

properties of prototype oxygen vacancies, primarily as they behave in

either a crystalline quartz environment, or in small clusters that

serve as a substitute for a real amorphous structure. To date at least

three categories of E´ centers, existing at or above room temperature,

have been observed in SiO2 . The unifying feature is an unpaired

electron on a threefold coordinated silicon atom, having the form O3 ?

Si*. Feigl et al. identified the E´1 center in crystalline a-quartz

as a trapped hole on an oxygen vacancy, which causes an asymmetrical

relaxation, resulting in a paramagnetic center. The unpaired electron

in the E´1 center is localized on the three-fold coordinated Si atoms,

while the hole is localized on the other Si atom.

Results from an ab initio statistical simulation examination of the

behaviors of oxygen vacancies, within amorphous structures, identify a

new form of the E´-center, the E´g5, and help in the understanding of

the underlying physical mechanisms involved in switched-bias

annealing, and electron paramagnetic resonance (EPR) studies. The

results also suggest a common border trap, induced by trapped holes in

SiO2, is a hole trapped at an O vacancy defect, which can be

compensated by an electron, as originally proposed by Lelis and

co-workers at Harry Diamond Laboratories.

This dissertation provides new insights into the basic mechanisms of

a-SiO2 defects, and provides a link between basic mechanisms and

Electronic Design Automation (EDA) tools, providing an enhanced design

flow for radiation-resistant electronics.

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