Hydrogenated IGZO Thin-Film Transistors Using High-Pressure Hydrogen Annealing

Abstract

Hydrogenation of thin-film indium–gallium–zincoxide (IGZO) is carried out by applying a high-pressure hydrogen annealing (HPHA) process under 5-atm pressure at different temperatures of 260 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex> </formula> , 270 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> , and 280 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> . The HPHA effectively increases the carrier concentration and the Hall mobility up to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim}{10}^{19}~{\rm cm}^{-3}$</tex> </formula> and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim}{6.4}~{\rm cm}^{2}/{\rm Vs}$</tex></formula> , respectively. The HPHA-IGZO films exhibit smoother surfaces as compared with the as-grown films. The HPHA performs at a temperature of 260 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> that greatly enhances the electrical characteristics of IGZO TFTs, leading to a saturation field effect mobility of 7.4 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\rm cm}^{2}/{\rm Vs}$</tex></formula> , a subthreshold slope of 0.37 V/decade, a threshold voltage of 2.2 V, and an <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$I_{{\rm ON}}/I_{{\rm OFF}}$</tex></formula> of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$2.0\times 10^{6}$</tex></formula> .