Application of secondary electron imaging to dopant profiling of semiconductors

Doping-dependent contrast in secondary electron images of p/n junctions in silicon was observed and characterized. Secondary electron contrast profiles of in-situ boron doped epitaxial silicon structures showed an excellent correlation with spreading resistance and SIMS profiles. The magnitude of the contrast scaled with carrier concentration and the precision in locating the abrupt p(+)/n junctions was approximately 10 nm. The sensitivity of the technique extends to a carrier concentration of similar to 10(16) cm(-3) under optimum conditions. This phenomenon is employed to extract two-dimensional dopant profiles of suitable test structures.