Improvement in Characteristics of Polycrystalline Silicon Thin-Film Transistors by Heating with High-Pressure H₂O Vapor

Abstract

A heat treatment with high-pressure H 2 O vapor at temperatures of 190 °C to 270 °C was applied to improve the characteristics of n-channel polycrystalline silicon thin-film transistors. The heating at 190 °C with 3.6×10 5 Pa H 2 O vapor increased the carrier mobility from 50 cm 2 V -1 · s -1 (as fabricated) to 412 cm 2 V -1 · s -1 and reduced the threshold voltage from 2.2 V to 1.1 V. The drain current at negative gate voltages caused by the heating with high-pressure H 2 O vapor was reduced by additional heating at 300 °C as well as at 350 °C with H 2 O vapor at one atmospheric pressure. This annealing process resulted in an on/off drain current ratio of 10 7 .