Fabrication of a-Si:H Thin Film Transistors on 4-inch Glass Substrates by a Large Area Ion Doping Technique

Abstract
We developed a large area ion doping apparatus with an rf ion source of 50 cm in diameter. Charge accumulation during ion doping was suppressed by using a double grid. We fabricated a-Si:H TFT's on a 4-inch glass substrate by using the doping apparatus. By optimizing the thickness of the passivation film of TFT's, a field effect mobility, threshold voltage and an ON/OFF current ratio of 0.6 cm2/V·s, 4.9 V and 107, respectively, were obtained. We confirmed the uniformity of electrical properties for TFT's on 4-in. glass substrates to be about ±2%. These characteristics of TFT's are suitable for switching elements in a large area LCD.

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