Advancing the Understanding of Reliability in BEOL-Compatible Oxide Semiconductor Transistors: The Impact of AC PBTI

This article presents an in-depth investigation into the impact of alternating current (ac) and direct current (dc) positive bias temperature instability (PBTI) on hydrogen (H) formation in oxide semiconductor field-effect transistors (OSFETs). Utilizing highly stable co-sputtered indium-gallium–zinc-tin oxide (IGZTO) FETs, we provide a systematic and holistic analysis that reveals key differences between ac and dc PBTI effects, particularly at high temperatures (T). Our study uncovers several critical findings: 1) ac and dc PBTI exhibit distinct phenomena associated with the H formation at high T; 2) ac PBTI could mitigate the H formation, with both frequency (f) and duty factor (DF) significantly influencing the extent of the mitigation of the H effect; 3) DF demonstrates a more substantial impact compared to f in ac PBTI; and 4) up to 99.2% of the negative threshold voltage shift (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\text {th}}$ </tex-math></inline-formula>) induced by H formation could be alleviated by replacing dc PBTI with ac PBTI (25%, 1 MHz). These findings provide significant insights into the mechanisms of the H effect under different PBTI conditions.