Thin Film Transistors with High Mobility and High Threshold Voltage Stability Made Using Hot Wire Chemical Vapor Deposition

Although thin film transistors (TFT) are routinely made for commercial applications by plasma deposition, there is a need for TFTs with higher electron mobility as well as excellent stability. In this paper it is shown that hot-wire chemical vapor deposition (CVD) (Cat-CVD) can address those needs, while at the same time offering higher deposition rates and better source gas utilization. Thin film transistors with the active layer deposited either from pure SiH 4 or from H 2 -diluted silane show remarkable stability. The field-effect mobility in an inverted staggered configuration for amorphous channel material is 1.5 cm 2 V -1 s -1 and in the coplanar, top gate configuration it is 1.3 cm 2 V -1 s -1 . For µc-Si:H material in the top gate configuration, the as-deposited, unannealed mobility was ∼5 cm 2 V -1 s -1 , but recently also higher mobilities have been reported. Hot wire deposited channel layers are compatible with plasma-deposited SiN x layers, but also hot wire CVD SiN x with high density and compactness has been demonstrated. Thus it is feasible to produce all-hot-wire CVD TFTs directly on glass or polyimid.