The relation between positive charge and breakdown in metal-oxide-silicon structures

Abstract

The relation between positive-charge accumulation at the Si-SiO2 interface and the occurrence of high-field breakdown in metal-oxide-silicon structures has been investigated. Oxides having different hole-trapping properties were prepared with the addition of short rapid thermal anneals in O2. Experiments testing hole trapping, high-field stressing, the initial current transients at constant gate voltage, and breakdown statistics were performed on these oxides to examine the correlation between positive charge and breakdown. The conclusion is that positive-charge generation is only one of the processes occurring during high-field stress but is not the main cause for breakdown. Large current increases were observed for oxides that have large hole-trapping efficiencies, but the current increase is followed by fast current decay. The mechanism causing the current decay was investigated and was found to be an intrinsic mechanism which is related to the neutralization of the positive charge. These processes always accompany the formation of positive charge and explain why the effectiveness of the positive charge in causing current runaway is inhibited.