In-situ strain analysis with high spatial resolution: A new failure inspection tool for integrated circuit applications

A new non-destructive technique to measure strain over small areas of specimens in the scanning electron microscope (SEM) is described. By integrating new advances in secondary electron detection, imaging of insulating oxide layers and a methodology of generating an optical moiré fringe effect in the SEM, a strain analysis technique has been developed. Using classical methodologies of strain analysis of moiré fringes established in experimental elasticity studies, we demonstrate that one can quantitatively estimate localized strains due to mechanically induced damage with very high strain and spatial resolution sensitivities in a non-destructive fashion. The imaging of the moiré fringes is accomplished by voltage contrast methods. The usefulness of this technique in rapid assessment of localized strains, especially as an in-situ measurement tool in semiconductor failure analysis, is discussed.