DOI: 10.1002/cvde.201407115 Full Paper Atomic Layer Deposition of TiO 2 and ZrO 2 Thin Films Using Heteroleptic Guanidinate Precursors** By Mikko Kaipio, Timothee Blanquart*, Manish Banerjee, Ke Xu, Jaakko Niinistö, Valentino Longo, Kenichiro Mizohata, Anjana Devi, Mikko Ritala, and Markku Leskelä In this study the atomic layer deposition (ALD) of TiO 2 and ZrO 2 using two heteroleptic amido-guanidinate precursors, [Ti(NEtMe) 3 (guan-NEtMe)] and [Zr(NEtMe) 3 (guan-NEtMe)], together with water or ozone as oxygen sources, are investigated. All processes exhibit self-limiting growth at a deposition temperature of 275°C. The zirconium precursor especially gives high growth rates (0.8/1.0 Å per cycle with H 2 O/O 3 ). The films are also relatively smooth, as determined by atomic force microscopy (AFM). The composition of the films is examined using X-ray photoelectron spectroscopy (XPS) and time of flight elastic recoil detection analysis (TOF-ERDA). When using ozone as the oxygen source the films present very high purity. The results are compared and discussed with respect to earlier studies on guanidinate, as well as homoleptic amido precursors. Keywords: ALD, Guanidinate, Heteroleptic, Titanium dioxide (TiO 2 ), Zirconium dioxide (ZrO 2 ) 1. Introduction ALD is a CVD technique in which the precursors are pulsed into the reaction chamber alternately. [1] When the precursor-surface interaction is appropriate, film growth proceeds in a self-limiting manner and therefore the thickness of the film can be accurately controlled. The self-limiting surface reactions also ensure that uniform films are obtained over large area substrates with highly demanding three-dimensional structures. For these reasons, ALD is currently an essential method in the manufacturing of various microelectronic devices where thin film layers with thickness precision in the nanometer scale are needed. [1] Titanium dioxide (TiO 2 ) and zirconium dioxide (ZrO 2 ) are high-k dielectric materials with several potential applications in the microelectronics industry, such as in dynamic random access memory devices, capacitors, and metal oxide semiconductor field-effect transistors. [2,3] Novel ALD precursors for the deposition of TiO 2 and ZrO 2 thin films should be developed because a wide range of precursor characteristics are needed, such as high thermal stability, suitable crystallization behavior of the film, and high growth rate. [3] In addition, the influence of the oxygen precursor needs to be investigated as it can have an effect on film purity, crystallization temperature, and growth behavior. [4] Developing better ALD processes for any given material is a question of making systematic studies on different precursors. Recently, heteroleptic compounds have gained considerable attention when more efficient metal precursors for ALD have been sought. Ideally, a heteroleptic precursor should display the best properties of its different ligands, while simultaneously the downsides of these ligands, e.g., poor thermal stability, should be suppressed. The molecular properties one tries to affect by substituting one or more ligands of a homoleptic precursor are most commonly volatility, thermal stability and reactivity. [5] In heteroleptic precursors two different ligands (denoted X and Y) are most commonly employed. When also taking into account the homoleptic precursors employing these ligands, the following five ligand permutations can be realized for 4þ oxidation state metal M and 1- ligands: MX 4 , MX 3 Y, MX 2 Y 2 , MXY 3 , and MY 4 . Although a large amount of information is available on the general characteristics of the most common ligands, finding the best candidate out of the precursors listed by just looking at the ligand combinations is extremely difficult. In principle, it is possible to make an evaluation of each one in-silicon, but quantitative [*] Dr. T. Blanquart, M. Kaipio, J. Niinistö, Prof. M. Ritala, Prof. M. Leskelä Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014, Helsinki (Finland) E-mail: timothee.blanquart@gmail.com M. Banerjee, Dr. K. Xu, Prof. A. Devi Inorganic Materials Chemistry, Ruhr-University, Bochum D-44780, Bochum (Germany) V. Longo Department of Applied Physics, Technische Universiteit, Eindhoven P.O. Box 513, 5600 MB Eindhoven, (The Netherlands) Dr. K. Mizohata Division of Materials Physics, Department of Physics, University of Helsinki, FI-00014, Helsinki (Finland) [**] The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007- 2013) under Grant Agreement ENHANCE-238409. The research has also been supported by Finnish Centre of Excellence in Atomic Layer Deposition. Chem. Vap. Deposition 2014, 20, 209–216 © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com 209