Atomic origin of high temperature electron trapping in MOS devices

TL;DR

This paper investigates the atomic-scale mechanisms behind increased electron trapping in high-temperature MOSFETs, revealing that oxygen vacancies in SiO2 play a key role in device degradation at elevated temperatures.

Contribution

It provides first-principle calculations linking oxygen vacancy reconfiguration to electron trapping, advancing understanding of high-temperature MOS device reliability.

Findings

Enhanced electron trapping involves thermally activated second-electron capture.

Oxygen vacancies transform into new structures with Si dangling bonds at high temperatures.

Structural reconfigurations of oxygen vacancies are crucial for device degradation.

Abstract

MOSFETs based on wide band-gap semiconductors are suitable for operations at high temperature, at which additional atomic-scale processes that are benign at lower temperatures can get activated which results in device degradation. Recently significant enhancement of electron trapping was observed under positive bias in SiC MOSFETs at temperatures higher than 150{\deg}C. Here we report first-principle calculations showing that the enhanced electron trapping is associated with thermally activated capturing of a second electron by an oxygen vacancy in SiO2, by which the vacancy transforms into a new structure that comprises one Si dangling bond and a bond between a five-fold and a four-fold Si atoms. The results suggest a key role of oxygen vacancies and their structural reconfigurations in the reliability of high-temperature MOS devices.