2-DIMENSIONAL PROFILING USING SECONDARY ION MASS-SPECTROMETRY

As device dimensions decrease and packing densities increase, the need for accurate mapping of dopant profiles in at least two dimensions is becoming ever more acute. Such data are required to establish the limitations of very large scale integrated manufacture, and to verify and refine the process simulators which have been devised. However, direct measurements of dopant atom distributions, using analytical techniques such as secondary ion mass spectrometry, are not possible owing to the limited analyte volume available at high spatial resolutions. The technique described here uses a specially fabricated sample which allows material to be collected from a large number of similar volumes, thus improving the sensitivity. The geometry magnifies the lateral spread many times increasing the lateral resolution achieved with a probe of a given diameter. Relatively low energy probes may be used to obtain high depth resolutions. In subsequent processing, sensitivity, depth, and lateral resolution may be mutually traded to optimize the profile for a given application.