Quantitative Evaluation of Cobalt Disilicide/Si Interfacial Roughness

Abstract

The formation of smooth, conformal cobalt disilicide (CoSi 2 ) without facets or voids is critical for microelectronic device reliability owing to the ultra-shallow contact areas. Here we demonstrate the formation of smooth and conformal CoSi 2 films by chemical vapor deposition (CVD) of cobalt nitride (Co x N) films on silicon (Si) or on silicon on insulator (SOI) substrates, followed by in-situ rapid thermal annealing (RTA) at 700°C. To reveal the CoSi 2 /Si interfacial morphology, we report a back-to-front sample preparation method, in which mechanical polishing, anisotropic tetramethylammonium hydroxide (TMAH) wet etching, hydrofluoric acid (HF) wet etching, and isotropic xenon difluoride (XeF 2 ) dry etching are employed to remove the SOI substrate from the back side to expose the CoSi 2 /Si interface. This method offers a robust and reliable procedure for quantitative assessment of the CoSi 2 /Si interfacial roughness, as well as analytical support for advanced fabrication process development.