Atmospheric pressure spatial ALD of Al2O3 thin films for flexible PEALD IGZO TFT application

Abstract

Atmospheric pressure spatial atomic layer deposition (AP S-ALD)-derived Al2O3 films were investigated on the growth temperatures (100 °C ∼ 200 °C) and demonstrated as the gate insulator for IGZO thin film transistor (TFT) applications. When the growth temperature increases to 200 °C, growth per cycle (GPC) and refractive index of the Al2O3 films were 1.33 Å/cycle and 1.63, respectively. The film density also increased from 2.55 g/cm3 to 2.79 g/cm3 on the growth temperature, which decreasing the carbon impurities of the Al2O3 film (100 °C: 3.57 at%, 150 °C: 1.73 at%, 200 °C: N/A). In addition, the impurity and low growth temperature may degrade not only film surface roughness, but also electrical characteristics. As the buffer and gate insulator Al2O3 layers, the IGZO TFT were fabricated on a polyimide substrate. The IGZO TFTs with the Al2O3 layers showed excellent device performances: 52.48 cm2/V.sec of field effect mobility, −3.09 ± 0.14 of threshold voltage, and 0.14 ± 0.01 subthreshold swing. In addition, the TFT exhibited excellent bias reliability and mechanical bending stability. This highly stability will be attributed to AP S-ALD Al2O3 acting as an excellent insulator.