A study of junction photocurrent changes caused by defective gate oxide

It has been widely revealed that the Atomic Force Microscope (AFM) laser beam may induce photoperturbation which can significantly deteriorate the characterization accuracy of AFM-based tools. This paper gives direct evidence that the optical excitation process may yield a temporary source of minority carriers, and that the inversion layer can be formed beneath the oxide layer of the NMOS transistor. By taking advantage of this non-negligible photoelectric effect, a novel approach that is likely to be used to evaluate gate oxide quality or gate oxide reliability was developed. In this study, it was observed that defective gate oxide can cause junction photocurrent changes, or the junction photocurrent can be correlated to gate oxide quality.