Back-Channel-Etched Oxide Thin Film Transistors with a Corrosion Resistant Crystalline InGaO Channel

A crystalline indium-gallium-oxide (InGaO) was used as the channel of a thin film transistor (TFT) with back-channel-etched (BCE) structure. The effects of deposition temperature (T) on crystal structure, morphology, electrical properties and corrosion resistance of InGaO films were studied in detail. X-ray diffraction spectra and scan electron microscopy reveal that the slight increase in corrosion resistance with Tat 25–200°C results from the discrete crystallites embedded amorphous network while the massive increase at 290°C results from the high crystallinity of the film. The carrier concentration (Nc) and mobility of InGaO films show a huge increase as Tincreases due to the crystallization process at 25–200°C, but they change very little when the films are highly crystallized at 290°C. The BCE TFT exhibits a slightly higher saturated mobility of 11.9 cm2/(V·s), a more positive threshold voltage of −0.43 V, a larger subthreshold swing of 0.37 V/decade and a higher off-current of 4 pA when compared with the TFT fabricated by a lift-off process. Combined with X-Ray Photoelectron Spectroscopy analysis, the BCE process causes an oxygen-deficient back channel and introduces deep trap states, leading to the deterioration in electrical performance.