Application of electro optical frequency mapping (EOFM) in scan chain failure analysis for ASIC

Abstract

This paper describes the use of Electrical Optical Frequency Mapping (EOFM) in amplitude and phase mode to binary search the broken scan cell and missing clock activities in scan-chain failure for Application-Specific Integrated Circuit (ASIC) die inside the sensor device. Due to the smaller size of the ASIC die at the bottom stack of the GCELL and the Evaluation Board (EVB) design which not favorable for higher Numerical Aperture (NA) objective lens analysis, it limits the use of FA techniques such as top side probing and Electro Optical Probing (EOP) using Solid Immersion Lens (SIL). Due to these limitation, the EOFM by using airgap lens from backside is evaluated to compliment the top side probing analysis or EOP using SIL. It is observed both the phase and amplitude mode in EOFM will assist in isolating the faulty scan cell and faulty scan clock module. Two case studies presented in this paper will demonstrate how the EOFM helps to isolate the broken scan cell and the missing clock module.