Suppressing Undesired Channel Length-Dependent Electrical Characteristics of Fully Integrated InGaZnO Thin-Film Transistors via Defect Control Layer

Demand for increased scalability of oxide thin-film transistors (TFTs) continues to rise, along with the need for ever-higher integration densities and driving currents. However, the undesirable channel length (L-CH)-dependency renders short channels difficult. To overcome such behavior in back-channel etched devices, back-channel interface engineering using commercially favorable silicon oxide (SiOx) and the effects thereof on the electrical characteristics of fully integrated TFTs are investigated. Process-dependent investigation reveals that a sequential formation of double-layered SiOx with a defect control layer (DCL) effectively alleviates back-channel damage. The proposed method imparts advanced functionality to conventional materials of SiOx. The DCL promotes oxygen inter-diffusion to the oxygen-deficient back-channel, suppresses excess hydrogen inflow, and boosts out-diffusion of residual copper from the back-channel. This afforded excellent device uniformity and electrical characteristics with the proposed device, including field effect mobility of approximate to 14.0 +/- 1.0 cm(2) V-1 s(-1), threshold voltage (V-th) of approximate to 1.22 +/- 0.39 V, and subthreshold gate swing of approximate to 0.46 +/- 0.09 V dec(-1) at W/L = 4/7 mu m. Furthermore, V-th variation when L-CH decreased from 20 to 4 mu m is dramatically suppressed from >11.39 V with the pristine device to 0.78 V with the proposed device, because of controlled back-channel properties providing sufficient effective L-CH.