Low energy deposition of InGaZnO channel layer using linear facing target sputtering for oxide TFTs

We suggest a linear facing target sputtering (LFTS) technique to deposit InGaZnO (IGZO) channel layer on the gate dielectric without plasma damage to produce oxide TFTs (OxTFT). Due to effective confinement of high-density plasma between facing IGZO targets and substrate position outside of the plasma formation region, the IGZO channel layer was deposited on the SiO2 dielectric layer without plasma damage or substrate heating caused by severe bombardment of energetic particles. The LFTS-grown IGZO film showed a complete amorphous structure and very smooth surface morphology due to the low temperature of the LFTS process. After 300 °C annealing under atmospheric ambient, the OxTFT with LFTS-grown IGZO channel layer had a field effect mobility (μFE) of 7.52 cm2/Vs, sub-threshold swing (SS) of 0.35 V/decade, on–off ratio (Ion/Ioff) of 9.86 × 109, and interface trap density (Dit) of 1.05 × 1012 eV−1 cm−2 which is comparable to results obtained for IGZO-based TFTs fabricated by tilted cathode DC sputtering. Our results indicate that LFTS is a promising low damage and low temperature sputtering technique for deposition of IGZO channel layer or other oxide channel layer directly on the gate dielectric layer for high performance OxTFTs.