LOW-TEMPERATURE POLYSILICON TFT WITH GATE OXIDE GROWN BY HIGH-PRESSURE OXIDATION

Polysilicon thin-film transistors (TFT's) have been fabricated with the maximum processing temperature limited to 650-degrees-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-degrees-C. The TFT's exhibit a mobility of 34 cm2/V.s, threshold voltage of 3.5 V, leakage current below 0.01 pA/mu-m, subthreshold slope of 0.18 V/decade, and an ON-OFF ratio of over 8 orders of magnitude. These values are comparable to those obtained with conventional polysilicon TFT's using high-temperature thermal oxidation.