Quantitative analysis of in-field defects in image sensor arrays

Growth of pixel density and sensor array size increases the likelihood of developing in-field pixel defects. An ongoing study on defect development in imagers has now provided us sufficient data to be able to quantify characteristics of defect growth. Preliminary investigations have shown that defects are distributed randomly and the closest distance between two defective pixels is approximately 79-340 pixels apart. Furthermore, from an observation of 98 cluster-free defects, the diameter of the defect is estimated to be less than 2.3% of a pixel size at 99% confidence level. The fact that no defect clusters were found in the study of various digital cameras allows us to conclude that defects are not likely to be related to material degradation or imperfect fabrication but are due to environmental stress such as radiation. Furthermore, as verified by a statistical study, the absence of defect clustering provides information on the size of defects and insight into the nature of the defect development.