Improvement of Thermal and Environmental Stabilities of Short Channel Coplanar Amorphous InGaZnO Thin-Film Transistors by Introducing Amorphous ZrAlO x Interlayer

The short channel coplanar amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) is reported by introducing a ZrAlO x (ZAO) interlayer deposited by spray pyrolysis at the substrate temperature of 350 degrees C. The atomic ratio (at. %) of In:Ga:Zn:O is 1:2.5:1.2:5.2 in the a-IGZO film deposited by sputtering. The a-IGZO TFT with ZAO layer with 0.87 mu m channel length exhibits the field-effect mobility of 6.44 cm(2) V-1 s(-1), the threshold voltage of -2.16 V, and on/off current ratio of 7.6 x 10(7). It is found from the X-ray photoelectron spectroscopy depth profile and high-resolution transmission electron microscope analysis that some Zr atoms diffuse into the a-IGZO underlayer. The formation of Zr-O bonds on a-IGZO surface region reduces the carrier concentration in the a-IGZO TFT offset region, between source/drain contact and the channel, and blocks the carrier diffusion into the channel. This reduces the field-effect mobility of 10 mu m channel length TFT from 21.86 to 14.01 cm(2) V-1 s(-1), but the ZAO layer protects the a-IGZO from the diffusion of H2O and O-2. As a result, 0.87 mu m TFT shows high on/off current ratio and stable under 85 degrees C and 85% relative humidity test for 2 days.

Automated summary

A short channel coplanar amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) with a ZrAlOx (ZAO) interlayer has been developed, showing high field-effect mobility and on/off current ratio, and demonstrating stability under testing conditions of 85 degrees Celsius and 85% relative humidity for 2 days.