Homogeneous and heterogeneous reactions in the decomposition of precursors for the MOCVD of high-k and ferroelectric films

The present paper reports on the role of heterogeneous and homogeneous reactions in the MOCVD of Sr(hfaC)(2)tetraglyme (H-hfac = 1, 1, 1,5,5,5-hexafluoroacetylacetone) and Ta(OC2H5)(5) precursors. Hints of the precursor decomposition during MOCVD processes in hot wall reactors have been obtained through in situ FT-IR monitoring of the gas phase composition. Two different reaction pathways have been proposed for the MOCVD of Sr(hfac)(2)tetraglyme. A heterogeneous decomposition mechanism is the most relevant process at low temperatures and/or in the presence of reactive surfaces (metal), while a homogeneous decomposition leading to CF2O and acylketenes is evident at high temperature and/or adopting less reactive surfaces. In the case of Ta(OC2H5)(5), the main pathway involves a heterogeneous process leading to C2H5OH, enhanced in presence of metallic surfaces. (C) 2002 Elsevier Science Ltd. All rights reserved.