Alcohol-assisted growth of copper CVD films

We report the effect of various alcohols on the transport mechanism and reaction kinetics of Cu(hfac)(2) reduction for copper CVD. A variety of transport experiments are performed, all of which indicate that the presence of alcohol does nothing to increase the vapor phase transport rate of Cu(hfac)(2). In contrast, steady-state kinetic measurements reveal a significant increase in CVD growth rates upon addition of an alcohol co-reactant, which we therefore attribute to an alcohol-assisted enhancement of the intrinsic kinetics of Cu(hfac)(2) reduction. For the series of alcohols studied, the enhancement factor increases in the order: MeOH < EtOH < i-PrOH; this correlates with the pK(a) values of the alcohols. The dependence of the growth rate on alcohol partial pressure is first-order, which can be described using a simple modification of our earlier Langmuir-Hinshelwood rate expression for H-2 reduction of Cu(hfac)(2). The revised expression is consistent with a mechanism in which the rate limiting step involves H+ transfer between an adsorbed alcohol molecule and the first dissociated (hfac) ligand from an adsorbed Cu(hfac)(2) molecule. (C) 1998 Elsevier Science S.A. All rights reserved.