High performance amorphous silicon image sensor arrays

We discuss approaches to improve the performance of amorphous silicon (a-Si) X-ray imagers. Imager size has been increased to 30 X 40 cm and the number of pixels to > 7 million. Processing improvements have nearly doubled the sensor fill factor land hence sensitivity) and have reduced the data line capacitance which is the principal contribution to the electronic noise of the system. With new thin film transition (TFT) technology both amorphous and polysilicon TFTs made with the identical structure, using laser recrystallization are produced. The hybrid approach allows smaller leakage current a-Si:H devices to be used for the pixel TFT. and high mobility polysilicon devices for peripheral electronics. Arrays incorporating a lead iodide X-ray photoconductor have promise for higher sensitivity provided the leakage current can be reduced. (C) 1998 Elsevier Science B.V. All rights reserved.