Stabilization of top-gate p-SnO transistors via ultrathin Al2O3 interlayers for hysteresis-free operation

Abstract

The integration of p-type oxide semiconductors is imperative for realization of complementary metal-oxide-semiconductor logic in monolithic 3D integrated circuits. Among the various p-type oxides, SnO has emerged as a promising channel material owing to its high hole mobility and back end of line compatibility. However, its metastable nature and susceptibility to oxidation pose substantial challenges, particularly in top-gate thin-film transistors (TFTs), where the SnO channel is directly exposed to oxidizing species during high-k HfO2 dielectric deposition. In this study, we introduce an ultrathin Al2O3 interlayer (IL) (1.5-3 nm) between the SnO channel and high-k HfO2 dielectric to mitigate this challenge. The IL enables the use of ozone as an oxidant during HfO2 deposition while preventing excessive SnO oxidation, and thereby preserving high-performance p-type conduction. Through the optimization of the interlayer thickness, we eliminated the hysteresis behavior and achieved a substantial enhancement in field-effect mobility and improvement in on/off current ratio. This study presents the first demonstration of a top-gate TFT featuring a p-type oxide channel fabricated via atomic layer deposition, enabled by the incorporation of an ultrathin Al2O3 interlayer. The findings underscore the pivotal role of interface engineering in the stabilization of p-type oxide semiconductors and provide insights into their practical implementation in advanced electronic devices.