Characterization of advanced complementary metal–oxide–semiconductor processes with reverse secondary ion mass spectrometry profiling

Abstract

Secondary ion mass spectrometry (SIMS) profiling from the backside of a wafer containing the silicon-on-insulator structure has proven to be a unique way to achieve high accuracy in the characterization of a through-gate-oxide phosphorous profile in a complementary metal–oxide–semiconductor (CMOS) gate stack [P. Ronsheim et al., J. Vac. Sci. Technol. B 20, 448 (2002)]. In this work, we extended the sample preparation method for reverse SIMS by including the traditional transmission electron microscopy dimpling technique and generated large area openings with good reproducibility. Details about the flatness of sample surfaces, electrical conductivity near the surface of polycrystalline Si films, and difference between frontside and reverse SIMS data were elaborated by profiling an annealed P-type metal–oxide–semiconductor gate sample with polycrystalline Si doped with boron. The capability of reverse SIMS was further evaluated by characterizing the Hf distribution at the interface of the HfO2/Si substrate and Cu diffusion in a Cu/Ta/SiO2/Si stack, two typical analytical requests from CMOS front-end and back-end processes that have been challenges to SIMS. It was demonstrated that reverse SIMS was a promising solution to the characterization of abrupt interfaces that used to be hindered by the large decay lengths dominated by beam-bombardment-induced diffusion, segregation, preferential sputtering, etc.