Detection and localization of gate oxide shorts in MOS transistors by optical-beam-induced current

The optical-beam-induced current (OBIC) technique in a scanning laser microscope enables gate oxide shorts in MOS transistors to be detected and localized, and confirms results of electrical measurements performed on failed devices. The technique is completely nondestructive and can be applied to all cases where a nonohmic contact is formed due to breakdown phenomena. It is demonstrated that the OBIC technique, coupled with device electrical characterization, can identify gate oxide failure sites in all cases where a junction is formed or can be electrically accessed between gate and other terminals. During the OBIC measurements, no device damage occurs: the device is kept unbiased, so that photo-generated carriers cannot achieve the energy necessary to be injected into oxides. No difference was found in MOS electrical characteristics measured before and after OBIC observations