The Role of Oxygen Vacancy and Hydrogen on the PBTI Reliability of ALD IGZO Transistors and Process Optimization

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 (
${V}_{\text {TH}}{)}$
shift under positive stress is found to be determined by both hydrogen (H) and oxygen vacancy (
$\text{V}_{\text {O}}{)}$
, which is the dominating factor with the highest time exponent in PBTI of IGZO transistors. By reducing H concentration and suppressing
$\text{V}_{\text {O}}$
generation by process engineering in gate-stack, semiconductor channel, and post-treatment condition, IGZO transistors with high PBTI reliability are demonstrated, achieving a low
$\vert \Delta {V}_{\text {TH}}\vert $
of 11 mV at 95 °C,
${V}_{\text {stress}}$
of 3 V (
${t}_{\text {ox}}$
= 7 nm, EOT = 3.2 nm by
${C}$
–
${V}$
measurements, and
${E}_{\text {OX}}$
of 3.7 MV/cm), and
${t}_{\text {stress}}$
of 2 ks.