Growth of ternary PbTiOx films in a combination of binary oxide atomic layer depositions

Abstract

Ternary PbTiOx films were deposited at 240°C on Pt-covered Si substrates using a combination of liquid injection atomic layer depositions of binary TiOx and PbO films. Ti(OC3H7)2(C11H19O2)2 [Ti(Oi−Pr)2(DPM)2] and Pb(C11H19O2)2 [Pb(DPM)2] dissolved in ethylcyclohexane and H2O were used as source materials. The deposition rates of Pb and Ti were enhanced in the ternary process compared to their binary processes under comparable deposition conditions. The Pb∕Ti ratio of PbTiOx films saturated with an increase in Ti precursor input, while it continued to increase with an increasing Pb precursor input. The self-regulated growth nature of the Pb–O layer in the binary film growth was lost in the mixed PbTiOx process as a result of interaction with the predeposited Ti–O layer. It was confirmed that for the PbTiOx film to grow on Pt substrates, an initial incubation period is required. Both Pb–O and Ti–O layers shared a common incubation period of up to ten sequences. The incubation period was shortened by increasing the input of Pb precursor. It was independent of the input of the Ti precursor and the order of precursor supply. This variable incubation period was considered as a potential key issue for growing stoichiometric and uniform multicomponent films over three-dimensional (3D) structures. The order of precursor supply affected the effective deposition rate after the incubation period. A sequence starting with a Ti precursor injection showed a higher growth rate than a sequence that started with a Pb precursor supply. A PbTiOx film was deposited on a 3D substrate precoated with an Ir layer to demonstrate the uniformity in film thickness and cation composition. Although the present PbTiOx process does not have an ideal wide-process window in the cation composition, the PbTiOx film showed uniform coverage and the distribution of cation composition over the hole structure was within ±10%.