The Role of Oxygen Vacancy and Hydrogen on the PBTI Reliability of ALD IGZO Transistors and Process Optimization
Zhiyu Lin, Lu Kang, Jinxiu Zhao, Yue Yin, Ziheng Wang, Jun Yu, Yuan Li, Guangzheng Yi, Arokia Nathan, Xiuyan Li, Ying Wu, Jeffrey Xu, Mengwei Si
Abstract
In this work, we demonstrate indium–gallium–zinc oxide (IGZO) transistors fabricated on an 8-in wafer with high uniformity, steep subthreshold slope, and high reliability under positive bias temperature instability (PBTI) stress. The impact of channel compositions, gate dielectrics, and post-treatment conditions on PBTI degradation is systematically characterized and analyzed. The negative threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {TH}}{)}$ </tex-math></inline-formula> shift under positive stress is found to be determined by both hydrogen (H) and oxygen vacancy ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\text {O}}{)}$ </tex-math></inline-formula> , which is the dominating factor with the highest time exponent in PBTI of IGZO transistors. By reducing H concentration and suppressing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\text {O}}$ </tex-math></inline-formula> generation by process engineering in gate-stack, semiconductor channel, and post-treatment condition, IGZO transistors with high PBTI reliability are demonstrated, achieving a low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \Delta {V}_{\text {TH}}\vert $ </tex-math></inline-formula> of 11 mV at 95 °C, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {stress}}$ </tex-math></inline-formula> of 3 V ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {ox}}$ </tex-math></inline-formula> = 7 nm, EOT = 3.2 nm by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> measurements, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {OX}}$ </tex-math></inline-formula> of 3.7 MV/cm), and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {stress}}$ </tex-math></inline-formula> of 2 ks.