We have fabricated high-performance amorphous silicon thin-film transistors (a-Si:H TFTs) on 2 mil. (51 μm) thick polyimide foil substrates. The TFT structure was deposited by r.f.-excited plasma enhanced chemical vapor deposition (PECVD). All TFT layers, including the gate silicon nitride, the undoped, and the n+ amorphous silicon were deposited at a substrate temperature of 150 °C. The transistors have inverted-staggered back-channel etch structure. The TFT off-current is approximately 10-12 A, the on-off current ratio is >107, the threshold voltage is 3.5 V, the sub-threshold slope is approximately 0.5 V/decade, and the linear-regime mobility is approximately 0.5 cm2 V-1 s-1. We compare the mechanical behavior of a thin film on a stiff and on a compliant substrate. The thin film stress can be reduced to one half by changing from a stiff to a compliant substrate. A new equation is developed for the radius of curvature of thin films on compliant substrates.
- amorphous silicon thin-film transistors
- a-Si:H TFTs
- excited plasma enhanced chemical vapor deposition