THE APPLICATION OF SURFACE ANALYTICAL TECHNIQUES TO SILICON TECHNOLOGY

Most modern semiconductor device engineering takes place in the top micron of the host wafer and involves the creation of regions whose composition varies over lateral dimensions which may be less than 0.5-mu-m. Normal to the wafer surface, large changes in matrix and impurity composition may occur in the space of a single atomic plane. In future, the fabrication of quantum dots and wires will result in active device features a few nm in extent. Such material developments need to be supported by parallel development in surface analytical techniques with high spatial resolution. There are, however, fundamental limitations to what can be achieved directly. For a destructive technique such as secondary ion mass spectrometry (SIMS), the analytical sensitivity and spatial resolution are determined by the analyte volume which needs to be consumed to achieve the necessary statistical precision. Moreover, the type of information obtained depends on the details of the interaction between the primary probe and the sample surface. In order to combine high spatial resolution with high sensitivity, special sample structures and modified instruments are required. Techniques need to be developed for accurately compensating for the effects on the analysis of large localized changes in conductivity in the materials. A multi-technique approach to semiconductor analysis is required both to investigate the limitations of the techniques themselves, and to fully describe the material properties.