First Direct Observation of Two Different Hydrogen-Related Processes Corresponding to the Negative V _TH Shift Under PBTI Stress in IGZO Transistors by Pd Hydrogen Spillover

In this work, we propose a new method to characterize the impact of hydrogen (H) on the positive bias temperature instability (PBTI) degradation of IGZO transistors by the spillover of H through Pd electrodes. In this method, the incorporation of H into IGZO channel can be controlled by the H concentration in the test chamber and the location of Pd electrodes. As a result, for the first time, we identify two different negative threshold voltage (V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf>) shift mechanisms on the same IGZO transistor, where both mechanisms are clarified to be originated from Hrelated defects. It is understood that different atomic bonding configurations of H might contribute to the different negative V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> shift components. The IGZO transistors in this work exhibit a record low PBTI ∣ΔV<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf>∣ of 18.4 mV at 1 ks under a stress electrical field (Eox) of 6 MV/cm and a high temperature of 150°C by an optimized process to suppress vacancy defects and H.