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-TH) shift under positive stress is found to be determined by both hydrogen (H) and oxygen vacancy (V-O) , which is the dominating factor with the highest time exponent in PBTI of IGZO transistors. By reducing H concentration and suppressing V-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 |Delta V-TH| of 11 mV at 95 C-degrees, V-stress of 3 V ( t(ox) = 7 nm, E-OT = 3.2 nm by C - V measurements, and E-OX of 3.7 MV/cm), and t(stress) of 2 ks.