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 (μ_FE) of 7.52 cm²/Vs, sub-threshold swing (SS) of 0.35 V/decade, on-off ratio (I_on/I_off) of 9.86 × 10⁹, and interface trap density (D_it) 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.