Interfacial reactions of cobalt thin films on BF+2 ion-implanted (001) silicon

Abstract

Interfacial reactions of cobalt thin films on BF+2 -implanted (001)Si have been studied by both cross-sectional and plan-view transmission electron microscopy as well as by sheet resistance measurements. The implantation-amorphous samples were found to favor the formation of CoSi2 at 400 °C and laterally uniform growth of the phase at higher temperatures. Two discrete layers of fluorine bubbles were observed in cobalt silicides in all BF+2 -implanted samples annealed at 400–800 °C. In 800–900 °C annealed samples, large bubbles were often observed to distribute near the CoSi2 grain boundaries. The results indicated that (1) fluorine atoms diffuse rapidly at a temperature as low as 400 °C, and (2) appreciable amounts of fluorine atoms are present with low solubility in cobalt silicides after annealing at 400–900 °C. The residual interstitial defects in BF+2 -implanted samples were completely annihilated by CoSi2 formation at 800–900 °C. The elimination of all interstitial defects in these samples is attributed to the injection of a high density of vacancies which were generated during silicide formation. The electrical resistivity of CoSi on blank silicon was measured to be about 350 μΩ cm. The presently measured electrical resistivity value is believed to be one of the most accurate values obtained for CoSi to date. Factors influencing the formation of cobalt silicides and defect structure are discussed.

Ultra Shallow Junction Formation Using Diffusion from Silicides: I . Silicide Formation, Dopant Implantation and Depth Profiling

“…However, bubbles were found in the vicinity of the surface, presumably because of fluorine from the BF2 implantation. Fluorine bubble formation was previously observed at CoSt2 grain boundaries after the silicide was formed on BF2-implanted silicon (35). The same results were obtained for TiSi2, Fig.…”

Ultrashallow SIMS Study of Implanted Dopants in NiSi/Si(100)

“…Increase of thermal stability of silicide layers on BF 2 + implanted silicon was reported also for CoSi 2 [7] and TiSi 2 [8]. The authors suggested a synergetic effect of B and F retarding the degradation of the silicide morphology.…”

Enhanced growth of CoSi2 thin films on (001)Si with Co/Au/Co sandwich structures

“…Typically, the first cobalt silicide phase to form on silicon substrate is Co 2 Si (300-450 1C) followed by CoSi (350-500 1C) and subsequent CoSi 2 (X550 1C) formation [3,4]. In addition, the phase transformation of high-resistivity CoSi ($150 mO cm) to low-resistivity CoSi 2 was found to occur according to nucleation-controlled kinetics [5].…”