Fault isolation is a critical step of failure analysis, which is most important for yield improvement for any new microelectronic device manufacturing. Conventionally, electrical faults are isolated by emission microscopy, liquid crystal, LIVA/TIVA and ORBIRCH etc. techniques after final test. As microelectronic devices are becoming more complicated and with multiple metal layers, failure analysis faces more challenges than before. These challenges are even tougher in wafer foundries because little device information is available. This makes yield ramp-up take longer time. Utilizing inline E-beam inspection equipment, the electrical faults can be captured at the source layer rather than after final test. E-beam inspection can be incorporated in the manufacturing line at any critical layer of front end and back-end. This paper describes the in-line E-beam inspection and presents three cases: (1) Gate-oxide issue, (2) Contact issue, and (3) Interconnect issue to demonstrate its application.