(622c) Supercritical CO2 Deposition Kinetics of Hafnium Oxide Films

The deposition of conformal thin metal or metal oxide films on topographically complex substrates is one of the key challenges for next generation microelectronic device fabrication. Current approaches include the physical evaporation, sputtering, chemical vapor deposition (CVD) for metal films, and atomic layer deposition (ALD) and the CVD for metal oxides. Each has its drawbacks. ALD for example, offers exceptional step coverage however its modest deposition rates are not well suited for all but the thinnest films.

It has been demonstrated by our group that supercritical fluid deposition (SFD) enables the conformal deposition of metal films at deposition rates that exceed 30 nm per minute. This is feasible because the reaction media, supercritical fluid, offers higher precursor concentration and reduces mass transfer limitations to the substrate surface. Detailed kinetics studies of copper and ruthenium systems revealed that the deposition reaction is first order with respect to precursor concentration at low concentrations and zero order at higher concentrations. Therefore, conformal metal films in demanding structures with high aspect ratio can be obtained with SFD technique.

Recently, we and others have extended SFD for the conformal deposition of a number of metal oxide systems including ceria, hafnia and titania. Here we report metal oxide deposition kinetics using hafnia a model system. Hafnia is of broad interest due to its high dielectric constant and large band gap. We measured deposition rates via high temperature hydrolysis using tetrakis(2,2,6,6- tetramethyl heptane 3,5-dionato) hafnium in a cold wall batch differential reactor. The deposited films were characterized using AFM, XRD, XPS, SEM and the film thickness was measured with profilometry.