SIMS backside depth profiling of ultra shallow implants

In secondary ion mass spectrometry depth profiling, a more accurate junction depth can be acquired by sputtering from the backside of the wafer [J. Vac. Sci. Technol. B 16 (1) (1998) 298]. This technique takes advantage of the better depth resolution of the leading edge as compared to the trailing edge [Nucl. Instrum. Meth. B 47 (1990) 223]. By using silicon-on-insulator (SOI) wafers, we have developed a backside depth profiling technique for studying ultra shallow implants. The abrupt interface of the SOI wafer and the large selectivity in chemical etching result in smooth after-etched surfaces, which facilitate high resolution SIMS profiling. The true dopant distribution of B 1 keV implants was studied by performing front and backside depth profiling using SOI substrates. The 7.5 and 0.5 keV O2+ primary ions were used at oblique incidence in a Cameca IMS-6f, with and without oxygen flooding and sample rotation. The effectiveness of backside SIMS profiling of the ultra shallow dopant implants using SOI substrates is evaluated.