High-throughput and performance InZnAlO thin film transistor on polyimide substrate via atmospheric pressure spatial atomic layer deposition

Abstract

An indium-zinc-aluminum oxide (IZAO) thin film with Al subcycle variations was fabricated using atmospheric pressure spatial atomic layer deposition (AP S-ALD). Aluminum was used as a carrier suppressor due to its cost-effectiveness and high oxygen dissociation energy. The growth behavior of the film was found to vary depending on the number of Al subcycles. Up to the Al 2 cycle, Zn atom etching by trimethylaluminum (TMA) delayed the Al2O3 growth, and Al2O3 growth occurred normally in the Al 3 cycle. IZAO thin film transistors (TFTs) with a top-gate bottom-contact structure were fabricated on polyimide (PI) substrates to evaluate the effect of Al subcycles on their electrical characteristics and reliability. The device exhibited optimal electrical characteristics and reliability with the smallest sub-gap density of states near the conduction band minimum of the Al 2 cycle, including a threshold voltage of −0.39 ± 0.20 V, field-effect mobility of 29.0 ± 1.4 cm2/Vs, subthreshold swing of 84.0 ± 6.0 mV/decade, and threshold voltage shift by positive bias-temperature stress of + 0.2 V. In addition, stable electrical characteristics were maintained in a sliding stress test of 50,000 cycles with a bending radius of 1 mm and a sliding speed of 30 rpm. In conclusion, a high-performance IZAO TFT with high throughput and applicability for flexible displays was successfully fabricated using AP S-ALD.