Date of Award

Spring 2004

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical and Computer Engineering

First Advisor

Durgamadhab Misra

Second Advisor

Leonid Tsybeskov

Third Advisor

Marek Sosnowski

Abstract

This work investigates the screening of hot carrier stress degradation in n-channel MOSFETs when the devices were exposed to plasma processing. Devices with various antenna ratios were subjected to current stress (both gate injection and substrate injection) while the source and drain terminals were reverse biased by a screening potential followed by hot carrier stress. It was observed that screening of the drain edge was effective for both gate injection and substrate injection at different screening potentials. The hot carrier lifetime is directly related to interface state density (Dit), measured by charge pumping method. The results suggest that hot electron degradation could be severe or mild for devices affected by plasma damage depending on their exposure to the level of screening potential.

This work also investigates the screening of Si-H bond concentration for polarity-dependent high field electron injection under effective screening potentials. It was observed that Si-H bond concentration varies based on the screening of the source and the drain edges during current stress when a reverse bias potential is applied to the source and drain terminals. The interface state density (Dit), measured by charge pumping method, is found to have strong dependence on the concentration of the Si-H bonds. Hot carrier stress that significantly contributes to Si-H bond breaking confirmed the effective screening. The results also indicate that Si-H bond breaking mechanism during screening is dependent on the polarity of the current stress and the screening potential applied.

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