Voltage contrast (VC) is a useful technique and used widely in failure analysis of integrated circuit (ICs). This paper will demonstrate different FIB current intensities in a specific VC case and, by means of the technique, locate possible defect sites quickly. With the help of conductive atomic force microscopy (C-AFM), we can get an electrical verification at the same time. We discuss the relationship of VC and C-AFM as well as what the root cause of failure is in this case.

SRAM memory is an ideal vehicle for defect monitoring and yield improvement during process development because of its highly structured architecture. However, the success rate of defect detection, especially for soft single-column failures, is decreasing when traditional physical failure analysis (PFA) with only the bitmap is available for guidance. This is due to a variety of invisible or undetectable defects that cause leakage in the device. In order to understand the leakage behavior in advanced high voltage (HV) processes, a Conductive Atomic Force Microscope (C-AFM) [1-4] is introduced to perform junction-level fault isolation prior to attempting PFA. According to J. P. Morniroli [5], crystalline defects affect convergent-beam electron diffraction (CBED) and large angle convergent-beam electron diffraction (LACBED) patterns, so CBED and LACBED techniques were also applied to the specimens containing dislocations to allow further characterization of these defects. In this study quantified data extracted using the C-AFM is also used to establish a connection between the failure mechanism discovered and the soft single column failure mode.