Role of in-situ hydrogen plasma treatment on gate bias stability and performance of a-IGZO thin-film transistors

Abstract

This work investigates the effect of an<i>in situ</i>hydrogen plasma treatment on gate bias stability and performance of amorphous InGaZnO thin-film transistors (TFTs) deposited by using atmospheric-pressure PECVD. The H₂plasma-treated<i>a</i>-IGZO channel has shown significant improvement in bias stress induced instability with a minuscule threshold voltage shift (Δ<i>V</i>_th) of 0.31 and -0.17 V under positive gate bias stress (PBS) and negative gate bias stress (NBS), respectively. With the aid of the energy band diagram, the proposed work demonstrates the formation of negative species O₂^-and positive species H₂O⁺in the backchannel under PBS and NBS in addition to ionized oxygen vacancy (V_o) defects at<i>a</i>-IGZO/ZrO₂interfaces are the reason for gate bias instability which could be effectively suppressed with<i>in situ</i>H₂plasma treatment. From the experimental result, it is observed that the electrical performance such as field-effect mobility (<i>μ</i>_FE), on-off current ratio (<i>I</i>_on/<i>I</i>_off), and subthreshold swing improved significantly by<i>in situ</i>H₂plasma treatment with passivation of interface trap density and bulk trap defects.