Interlayer Mediated Epitaxy of Cobalt Silicide on Silicon (100) from Low Temperature Chemical Vapor Deposition of Cobalt

This paper reports the development of a methodology for the growth of epitaxial CoSi2 that uses Co films deposited by low temperature (390°C) chemical vapor deposition (CVD) from cobalt tricarbonyl nitrosyl [Co(CO)3NO] as source precursor. This CVD process exploits the reaction kinetics associated with the adsorption and decomposition of CoCO)3NO on Si surfaces to ensure the in situ, sequential growth of an ultrathin interfacial oxide layer followed by a Co thin film in a single deposition step. It is demonstrated that this interlayer, consisting of a Si–O or a Co-Si-O phase, inhibits silicidation for uncapped CVD Co regardless of annealing times and temperatures. Instead, Co agglomeration is observed, with the degree of agglomeration being proportional to the annealing temperature. The agglomeration is due to a reduction in the overall energy of the system through decrease of the Co/substrate interfacial area. Alternatively, for Ti/TiN capped CVD Co samples, the interfacial layer appears to play a role similar to that observed for similar layers in interlayer mediated epitaxy (IME). This assessment is supported by the observation of epitaxial CoSi2 for capped CVD Co samples after a single-step anneal at 725°C for 30 s. In contrast, Ti/TiN capped PVD Co samples annealed under identical processing conditions exhibited a polycrystalline CoSi2 phase with a strong (200) texture. As such, the methodology presented herein represents a modified IME technique for the growth of high quality, epitaxial CoSi2 films for applications in emerging microelectronics device technologies