快速熱製程氧化層之均勻度與應力效應研究 (2/3)
Date Issued
2004-07-31
Date
2004-07-31
Author(s)
DOI
922215E002005
Abstract
There are four major topics investigated in this work, i.e., the effect of oxidation temperature on the stress variation of ultra-thin oxides, the effect of pressure on the stress variation of ultra-thin oxides, the effect of scribing across the wafer on the reliability of MOS devices with ultra-thin gate oxides, and the novel technology of oxidation under stress. The wafer was oxidized in a rapid thermal process system and then MOS structures are performed after Al metallization and patterning. The positively biased substrate injection current versus the negatively biased gate injection current was plotted to find the stress characteristics. Generally, the positively biased substrate injection current will be saturated due to the insufficient supply of minority carriers. Oxidation will cause the damage of the substrate surface and therefore introduce defects or stress on the substrate surface. That will affect the above saturation current significantly. So, stress characteristics can be observed via the analysis of substrate injection saturation current behavior. It was found that for low temperature oxidation, the oxide thickness is non-uniform but the damage of surface is small. However, when the temperature is raised, the oxide thickness becomes large that makes the gate injection currents become uniform. The oxidation-induced damage to substrate surface is more severe than low temperature, so the positively bias substrate injection currents become non-uniform. For the issue of pressure, it was found that the effect of low pressure is similar to low temperature, while high pressure is vise versa. For the effect of scribing, it was found that the MOS devices located along the scribing line are more easy to be affected by scribing than those faraway from the line. The effects include the reduction of gate injection current, the increase of substrate injection current, and the reduction of accumulation capacitance. It is important to the consideration of package and is worthy of further investigation. In this work, a novel technology of oxidation under mechanical stress is proposed. The wafer was mechanically stressed during anodization to enlarge the lattice constant of Si to match that of SiO2 so that the SiO2/Si interface will become more perfect than without. It was found that the stressed oxidation samples exhibit less leakage and better reliability than those without. It is interesting for the oxidation engineering in preparing ultra-thin gate oxides.
Subjects
temperature effect
pressure effect
scribing effect
stressed oxidation technology
Publisher
臺北市：國立臺灣大學電子工程學研究所
Type
report
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