Effects of reaction kinetics on the microstructure of chemical vapour deposited copper films: experiment and simulation

Abstract

The microstructure of chemical vapour deposited copper films was studied using two different metalorganic precursors, namely bis(dipivaloylmethanato) Cu(II) or Cu(dpm)₂ and bis(t-butylacetoacetato) Cu(II) or Cu(tbaoac)₂. The microstructure of copper films deposited from Cu(dpm)₂ showed a strong dependence on growth temperature. Films deposited from Cu(dpm)₂ at 350°C are dense and well-connected. Increased growth temperature, however, yields larger grain size and higher degree of void incorporation into the films, resulting in higher electrical resistivity. Films grown at 450°C consist of well-separated and faceted grains. In contrast, growth rates of copper films grown from Cu(tbaoac)₂ were significantly lower (2 nm/min at 320°C for Cu(tbaoac)₂ as against 17 nm/min at 380°C for Cu(dpm)₂). Also, pyrolysis of Cu(tbaoac)₂ yielded Cu films with remarkably fine grain structure. In an attempt to understand the roles of chemical kinetics and the different atomic level processes involved in microstructural changes in copper films grown by chemical vapour deposition (CVD), a Monte Carlo simulation has been employed. Our simulation results confirm that chemical kinetics, along with surface and interface mobility of the growth species, play a pivotal role in determining the microstructure of copper films.