Investigation of copper layers deposited by CVD using Cu(I)hfac(TMVS) precursor

摘要

Chemical vapour deposition (CVD) of copper on titanium-coated substrates was performed in a stainless steel reactor using copper(I) hexafluoroacetylacetonate trimethylvinylsilane (Cu(I)hfac(TMVS)) as a precursor and nitrogen (N-2) as carrier gas. Film resistivity, film composition and surface morphology were studied in relation to deposition temperature, process pressure and process gas flow ratio. The lowest resistivity value obtained was around 2 mu Omega cm. In addition, cross-sectional examination of the copper films, using a LEO SEM imaging system, indicated increased film porosity at higher deposition temperatures. An optimum carrier gas flow rate was determined: higher carrier gas flow rates caused excessive dilution of the copper precursor, whilst lower carrier gas flow rates weakened the transport of the copper precursor to the substrate. XRD data revealed formation of copper oxide (Cu2O) if annealing temperatures exceeded 450 degrees C for a period of 30 min.FIB/TEM imaging revealed that CVD copper offers better conformality and viafilling than PVD copper in trenches 0.25 mu m wide and 0.5 mu m deep. CVD copper layers, passivated by a spin-on-glass dielectric, were shown to have reduced surface migration of copper atoms, compared to unpassivated layers. Copper films with a predominantly (111) orientation were found to exhibit a longer electromigration lifetime than copper films with mixed (111) and (200) orientations. (C) 2005 Springer Science + Business Media, Inc.