Electrical Characteristics of a-IGZO TFTs With SiO2Gate Insulator Prepared by RF Sputtering

Abstract

This study examined the electrical properties of a-IGZO thin-film transistors (TFTs) with a gate insulator of ${\hbox{SiO}}_{2}$ , in which a more TFT-industry-compatible sputtering technique was used for all processing steps. Instead of plasma enhanced chemical vapor deposition, a room-temperature sputtered ${\hbox{SiO}}_{2}$ gate insulator was used, which is more preferable for the simple and low cost process for oxide TFTs. The dielectric strength of the sputtered ${\hbox{SiO}}_{2}$ film with an oxygen ratio of 6.25% was 6.3 MV/cm, which is sufficient for a gate insulator. The a-IGZO TFTs with the sputtered ${\hbox{SiO}}_{2}$ gate insulators showed the optimal device parameters after post-annealing at $400^{\circ}{\hbox{C}}$ for 1 hour in air: saturation field-effect mobility of ${\hbox{3.80}}~{\hbox{cm}}^{2}/{\hbox{V}}\cdot{\rm s}$ , $V_{\rm th}$ of $-{\hbox{2.84}}~{\hbox{V}}$ , on/off ratio of ${\hbox{1.43}}\times {\hbox{10}}^{5}$ , and $S.S$ of 0.88 V/dec.