Optical charge-sensing method for testing of thin-film transistor arrays

Liquid-crystal displays (LCDs) using thin-film transistor (TFT) arrays are particularly attractive because they have the potential for picture quality almost equal to that of CRTs. At present, the problem with TFT-LCDs is that the yield and throughput of the TFT fabrication process are economically low. Several recent papers have described methods for testing and repairing TFT arrays, The technique described in this paper uses optical charge sensing as a practical method for functional testing of TFT arrays. It is expected that manufacturers will be able to improve TFT-array yields and reduce costs by using this technique to determine the location and type of defects in arrays. The technique can also be used to characterize TFT arrays