Application of Beam Deceleration to Improve SEM Image Quality for Physical Failure Analysis

Summary:

As technology nodes continue to shrink, Scanning Electron Microscopy (SEM) inspection and electrical characterization of transistors has increased in difficultly. This is particularly true with early back end-of-line (BEOL) features like metal and via layers which are traditionally imaged at 3-5 keV. At these layers, this energy is capable of beam contamination, introducing electrical complications particularly with transistor probing. This electrical data is necessary to characterize subtle defects at front end-of-line (FEOL). Thus, the implementation of beam deceleration for the inspection of these layers provides a useful combination of low landing energy and higher image quality. This technique proves to aid in preserving the ability to electrically characterize any defect at the subsequent layers beneath. This increases the quality of the Physical Failure Analysis (pFA) workflow when implemented at early BEOL layers by providing higher quality images as well as preserving the electrical properties of the transistors for subtle FEOL defect characterization.