Gate Oxide Instability against a Wide Range of Negative Electric Field Stress of SiC MOSFETs

Abstract

Negative bias temperature instability (NBTI) in 4H-SiC MOSFETs is investigated under a wide range of oxide electric field <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(E_{\text{ox}})$</tex> stress. The purpose of this study is to understand the capture and generation processes of quasipermanent electron and hole traps related to NBTI in SiC MOSFETs. For the first time, it is demonstrated that saturation and turnaround of threshold voltage shift <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\Delta V_{\text{th}})$</tex> can be universally described by the amount of charges injected into the gate oxide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(Q_{\text{stress}})$</tex> . Additionally, the generation processes of interfacial electron and hole traps are found to have two distinct phases. Finally, lifetime under NBTI testing is presented to exhibit a power-law relationship with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$E_{\text{ox}}$</tex> , resulting in longer lifetime than that predicted by the widely used E-model. The presented analyses enable appropriate modeling and electrical testing of NBTI in SiC MOSFETs.