Role of Self-Assembled Monolayers on Improved Electrical Stability of Amorphous In-Ga-Zn-O Thin-Film Transistors

Abstract

Self-assembled monolayers (SAMs) have been used to improve both the positive\nand negative bias-stress stability of amorphous indium gallium zinc oxide\n(IGZO) bottom gate thin film transistors (TFTs). N-hexylphosphonic acid (HPA)\nand fluorinated hexylphosphonic acid (FPA) SAMs adsorbed on IGZO back channel\nsurfaces were shown to significantly reduce bias stress turn-on voltage shifts\ncompared to IGZO back channel surfaces with no SAMs. FPA was found to have a\nlower surface energy and lower packing density than HPA, as well as lower bias\nstress turn-on voltage shifts. The improved stability of IGZO TFTs with SAMs\ncan be primarily attributed to a reduction in molecular adsorption of\ncontaminants on the IGZO back channel surface and minimal trapping states\npresent with phosphonic acid binding to the IGZO surface.\n