Low-temperature polysilicon TFT with gate oxide grown by high-pressure oxidation

Polysilicon thin-film transistors (TFTs) were fabricated with the maximum processing temperature limited to 650°C. Best results were obtained when the gate oxide was grown by a two-step high-pressure oxidation process, using high-pressure steam and then dry oxygen both at 15 atm and 650°C. The TFTs exhibit a mobility of 34 cm2/V × s, threshold voltage of 3.5 V, leakage current below 0.01 pA/μm, subthreshold slope of 0.18 V/decade, and an ON/OFF ratio of over eight orders of magnitude. These values are comparable to those obtained with conventional polysilicon TFTs using high-temperature thermal oxidation.