Ultra Shallow Depth Profiling by Secondary Ion Mass Spectrometry Techniques

Ultra shallow dopant profiles are one of the major challenges for ULSI silicon metrology. Following the ITRS 2002, the 90nm technology node will appear in 2004 along with the maximum drain extension in the range of 15-25 nm for both P-MOS and N-MOS devices. In this frame, a very abrupt junction with a decay length of 4 nm/decade is mandatory. A depth resolution better than 0.7 nm in profiling shallow implanted dopants is consequently required. In this review, after a brief summary on necessities and difficulties of (N-MOS) ultra shallow profiling for the 90 nm technology node, we present a comparison between two Secondary Ions Mass Spectrometry (SIMS) approaches using different instruments (Magnetic Sector and Time of Flight Spectrometers) for the characterization of arsenic ultra shallow profiles. A particular relevance is dedicated to the methodological optimization and data processing, mainly in quantification and depth scale determination. Quantitative SIMS results have been compared with complementary techniques like LEXES, MEIS and RBS.