A Review of Well Imaging Techniques

Abstract

The timely and accurate imaging of problems in p/n junctions is increasingly important. Scanning Capacitance Microscopy is a current standard for precise 2D-mapping of carrier profiles, but care must be taken to choose the correct field of view because of the slow scan time. This paper provides commentary on the usefulness and possible pitfalls of a wide range of techniques available to the modern FA analyst, with examples from problem solving in a process development environment. SEM passive voltage contrast may provide imaging of junctions, but may be limited to N-well / P-well after special sample prep. OBIRCH provides reliable information on any current flows, but may not be selective specifically to those involving junction problems. Electron Beam Induced Current provides junction information at SEM resolution, but it may be hard for subtle problems to not be swamped out by massive signals. Multi-photon OBIC shows promise for high-resolution laser-based imaging, but may require highly special wiring. Photon Emission is an old standby. A case study is given which shows that one must be careful to match camera type and defect mechanism type in order to be able to see actual junction leakage.