Improvement of Negative-Bias-Temperature Instability in SiN -Capped p-Channel Metal-Oxide-Semiconductor Field-Effect Transistors Using Ultrathin HfO2 Buffer Layer

Abstract

Characteristics of p-channel -capped metal-oxide-semiconductor field-effect transistors (PMOSFETs) with a thin buffer layer were investigated. The compressive strain in the channel was deliberately induced in this study by a capping layer over the gate using plasma-enhanced chemical vapor deposition (PECVD). Although a compressive capping effectively boosts the drive current of PMOSFET devices, its presence also worsens the negative bias temperature instability (NBTI) characteristics due to the high hydrogen content in the layer, which could diffuse into the channel region during the deposition process. To address this issue, the insertion of a thick buffer layer between the gate and capping is proposed and demonstrated to improve NBTI reliability without sacrificing the device performance enhancement.