Effect of Tensile-stress on MOS Capacitors with Rapid Thermal Ultra-Thin Gate Oxides
Date Issued
2008
Date
2008
Author(s)
Liu, Chien-Yu
Abstract
As MOS devices are scaled down to achieve high performance, the thicknesses of silicon dioxides are also scaled down. Besides, the growth temperature of thermal ultra-thin oxides is reduced to obtain better control. This trend results in gate leakage current increasing and unreliability. And the gate leakage current increasing would degrade devices’ electrical characteristics, the unreliability of oxides may make devices unstable in operation. In this thesis, a technique to improve the quality and reliability of SiO2 as ultra-thin gate dielectrics by bending the silicon wafer during rapid thermal oxidation is proposed. n Chapter 1, we introduce analysis models of MOS capacitors and experiment setup in this study, and calculate the strength of mechanical stress applied in this work. Then, in Chapter 2, the detailed electrical characteristics of MOS (p) structures with various oxidation processes are analyzed through C-V curves and I-V curves of samples. The different characteristics of MOS (p) structures, including flat-band voltage shift, leakage current, and oxide growth kinetics are found in this work. The experimental results show that the quality of oxides prepared by rapid thermal process can be improved by oxidation with mechanical tensile stress applied on silicon substrate. In Chapter 3, the reliability properties of tensile-stress MOS (p) samples, including time dependent dielectric breakdown (TDDB) and stress induced leakage current (SILC) are examined. After the test, it is found that the tensile-stress MOS (p) samples in the SILC and TDDB test maintain better quality in term of reliability than non-stress MOS (p) samples. In the last chapter, a conclusion and suggestions for future work are given.
Subjects
Tensile stress:MOS Capacitor:Rapid Thermal Ultra-thin Gate Oxides
Type
thesis
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