A Low Temperature Plasma-Assisted Deposition Process for Microcrystalline Thin Film Transistors, TFTS

The drive-current of low-temperature (∼300°C) deposited TFTs has been increased by replacing the a-Si:H channel, and source and drain materials with μc-Si. Lightly B2H6 doped, near-intrinsic μc-Si has been used as the channel layer of the TFTs, and n+ μc-Si was used for the source and drain contacts. The compensation of intrinsic defects in the undoped μc-Si by boron doping increases the dark conductivity activation energy from ∼0.35 eV to 0.8 eV. TFI's were fabricated in a bottom gate structure, and required an H2 plasma treatment to produce devices with effective channel mobilities of ∼6.8 cm2/V-s and threshold voltages of ∼3.7 V in the saturation region.