Rugged a-Si:H TFTs on plastic substrates

Much of the mechanical strain in semiconductor devices can be relieved when they are made on compliant substrates. We demonstrate this strain relief with amorphous silicon thin-film transistors (a-Si:H TFTs) made on 25-mu m thick polyimide foil, which can be bent to radii of curvature R down to 0.5 mm without substantial change in electrical characteristics. At R = 0.5 mm the channel area of the TFTs is strained by similar to 1%. The reduction in bending radius, from R similar or equal to 2 mm on steel foil of the same thickness, agrees with the theoretical prediction that changing from a stiff to a compliant substrate can reduce the bending strain in the device plane by a factor of up to 5.