Thin Film Transistors of Microcrystalline Silicon Deposited by Plasma Enhanced-CVD

Abstract

AbstractWe fabricated top gate TFTs of microcrystalline silicon (μc-Si) deposited at 360 °C. The TFTs have field-effect electron mobilities of up to 7.9 cm2/Vs in the saturation regime and 5.8 cm2/Vs in the linear regime. The highest ION/IOFF ratio is 105. Typical values for Vth is 6.5 V and for the subthreshold slope is 1.7 V/decade. The μc-Si is grown by PE-CVD from a source gas mixture of SiH4, SiF4 and H2, with a typical flow ratio of 1:20:200, at a pressure of 120 Pa and a power density of 160 mW/cm2. The TFT structure is built on un-passivated Coming 7059 glass, with 300 n+ μc-Si, 60 nm n+ μc-Si source and drain contact layers, 200 nm SiO2 or 300 nm SiNx gate insulator, and 100 nm Al gate, source and drain electrodes.