Combinatorial HV-CVD survey of barium triisopropyl cyclopentadienyl and titanium tetraisopropoxide for the deposition of BaTiO3

Barium titanate is a very promising material for the integration of optical communication into electronic integrated circuits. For a successful integration into CMOS compatible technology, a growth process has to be found which allows forming crystalline BaTiO3 at sufficiently low temperatures. We describe the combinatorial analysis of BaTiO3 formation by high vacuum chemical vapor deposition using barium triisopropyl cyclopentadienyl and titanium tetraisopropoxide as metal sources; water, oxygen, or ozone are used as oxidizing agents. We analyzed the impact of these oxidizing agents on the interaction of the precursor molecules on the substrate surface. Furthermore, we characterized the films concerning chemical composition and identified growth conditions leading to deposit composition corresponding to the stoichiometric BaTiO3 formation. XRD analysis confirms the formation of crystalline BaTiO3 phases for deposition temperatures as low as 370 °C.

Precursor adsorption efficiency of titanium tetra isopropoxide in the presence of a barium beta-diketonate precursor

Patrik Hoffmann, Yury Kuzminykh, Michael Oliver Reinke

Barium titanate is a promising candidate for integrated photonic application due to its high electro-optic coefficient; therefore the need arises for a suitable deposition technique which provides high film quality at low temperatures (below 500 degrees C) and reasonable growth rates. We report on combinatorial high vacuum chemical vapor depositions of titanium(IV) tetra isopropoxide and barium hexafluoroacetylacetonate (hfa)-tetraglyme on silicon substrates aiming at the deposition of barium titanate. The barium precursor was synthesized and characterized regarding its evaporation kinetics. Co-depositions of both precursors were carried out in the absence and presence of reactive gas partners such as H-2, H2O, O-2 and O-3. Plain substrates deposited in the absence of ozone, however, do not show any titanium incorporation. We call this phenomenon obviating precursor interaction. Elongated masking structures were designed and manufactured on silicon substrates to modify locally the precursor impinging rate of one of both precursors to study the nature of this obviating behavior. It was found, that the blocking results from a reduced sticking coefficient, i.e. a fast desorption of the precursor prior to decomposition. When adding ozone, distinct, sharply separated regions were identified on the substrate, which we separate, according to their chemical composition and morphology, into TiO2, Ba-containing and barium and titanium mixed deposit. We found that the transition between TiO2 and Ba-deposit is dependent on the titanium to barium precursor impinging ratio. Depending on the barium precursor flux, the third region of mixed deposition of barium and titanium forms in the Ba deposit. The mixed deposit indicates a promising starting point for a combinatorial high vacuum chemical vapor deposition optimization to evaluate the feasibility of a high quality barium titanate film by this technique. (C) 2013 Elsevier B.V. All rights reserved.

Elsevier Science Sa2013

Combinatorial Characterization of TiO2 Chemical Vapor Deposition Utilizing Titanium Isopropoxide

Patrik Hoffmann, Yury Kuzminykh, Evgeniy Ponomarev, Michael Oliver Reinke

The combinatorial characterization of the growth kinetics in chemical vapor deposition processes is challenging because precise information about the local precursor flow is usually difficult to access. In consequence, combinatorial chemical vapor deposition techniques are utilized more to study functional properties of thin films as a function of chemical composition, growth rate or crystallinity than to study the growth process itself. We present an experimental procedure which allows the combinatorial study of precursor surface kinetics during the film growth using high vacuum chemical vapor deposition. As consequence of the high vacuum environment, the precursor transport takes place in the molecular flow regime, which allows predicting and modifying precursor impinging rates on the substrate with comparatively little experimental effort. In this contribution, we study the surface kinetics of titanium dioxide formation using titanium tetraisopropoxide as precursor molecule over a large parameter range. We discuss precursor flux and temperature dependent morphology, crystallinity, growth rates, and precursor deposition efficiency. We conclude that the surface reaction of the adsorbed precursor molecules comprises a higher order reaction component with respect to precursor surface coverage.

ACS Publications2015

Precursor adsorption efficiency of titanium tetra isopropoxide in the presence of a barium beta-diketonate precursor

Patrik Hoffmann, Yury Kuzminykh, Michael Oliver Reinke

Elsevier Science Sa2013