Using dual plasma treatment to improve electrical characteristics and reduce flicker noise of high-kappa HfO2 LTPS-TFTs

Abstract

This study demonstrated the application of a dual plasma treatment to low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) comprising a self-aligned phosphorus implantation source and drain, high-kappa HfO2 gate dielectric, and aluminum metal gate. The dual plasma treatment involves a pre-deposition CF4 plasma treatment at a high-kappa/poly-Si interface and post-deposition N-2 plasma treatment at a high-kappa HfO2 gate dielectric; this treatment enables reducing the interface-trap-state defects at the high-kappa/poly-Si interface, grain boundary traps in the poly-Si channel film, and oxygen vacancy V-o in the high-kappa HfO2 gate dielectric. Thus, LTPS-TFTs with dual plasma treatment demonstrate excellent electrical characteristics such as threshold voltage, subthreshold swing, transconductance, driving current, and on/off current ratio. Flicker noise, also referred to as 1/f noise, caused by fluctuations of carriers transported in the grain boundary and the trapped carriers per unit oxide volume (N-t) can be suppressed. Therefore, high performance LTPS-TFTs subjected to dual plasma treatment can be appropriately applied to active matrix liquid phase-crystal display on system-on-panel technology. (C) 2015 Elsevier Ltd. All rights reserved.