TEM has not traditionally contributed to characterization of semiconductor junctions, except for some intriguing results by Perovic, Hull and Alvis where highly doped layers gave contrast under very specific sample preparation and imaging conditions. Since electron holography is sensitive to the phase of the electron wavefront that has passed through the sample, it has the potential to provide voltage contrast. In principle, given its inherent two-dimensional and quantitative character, electron holography is a strong candidate for analysis of semiconductor device junctions.

The sample for the work reported here was one of a group of test specimens fabricated at IBM for a dopant metrology round-robin comparison to evaluate various profiling methods. The substrate was <100> p-type silicon, boron-doped at 11-25 Ω-cm-1. The test structure was fabricated using low- temperature epitaxial growth and consisted of an abrupt p-n junction, formed by abutting 1020cm-3 doped regions of boron and phosphorus