Study of the Long-Term Electrical Stability of InGaZnO 3-D Film-Profile-Engineered Inverters

Abstract

IGZO 3-D film-profile-engineered (FPE) inverters were fabricated and characterized. The unipolar load and driver thin-film transistors (TFTs) were stacked vertically not only for the sake of saving footprint, but also for the flexibility of threshold voltage adjustment by the lengths of suspended hardmask. The proposed 3-1) inverters demonstrate full-swing switching with a voltage gain as high as 13.6 V/V at an operating voltage of 5 V. The long-term stability was investigated in terms of the voltage gain, transconductance (gm) and threshold voltage (Vth) shift. Following 4 months, degradation in the voltage gain of the inverter in company of reduced gm and positive Vth shift for the drive TFT is attributed to the outgassing of hydrogen.