Atomic Layer Deposition of Cerium Dioxide Film on TiN and Si Substrates: Structural and Chemical Properties
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Atomic Layer Deposition of Cerium Dioxide Film on TiN and Si Substrates: Structural and Chemical Properties Silvia Vangelista1, Rossella Piagge2, Satu Ek3,Tiina Sarnet3, Gabriella Ghidini2 and Alessio Lamperti1 1
CNR-IMM - MDM Laboratory, Via C. Olivetti 2, Agrate Brianza (MB) I-20864 Italy STMicroelectronics, Via C. Olivetti 2, Agrate Brianza (MB) I-20864 Italy 3 Picosun Oy, Tietotie 3, Espoo FI-02150 Finland 2
ABSTRACT Cerium dioxide (CeO2) thin films were deposited by atomic layer deposition (ALD) on both Si and TiN substrates. The ALD growth produces CeO2 cubic polycrystalline films on both substrates. However, the films show a preferential orientation along crystallographic direction for CeO2/Si or for CeO2/TiN. In correspondence, we measure a relative concentration of Ce3+ equals to 22.0% in CeO2/Si and around 18% in CeO2/TiN, by X-ray photoelectron spectroscopy. Such values indicate the presence of oxygen vacancies in the films. Our results underline the films differences and similarities between ALD-deposited CeO2 either on Si or TiN substrates, thus extending the knowledge on the CeO2 structural and chemical properties. INTRODUCTION In the last years, CeO2 based materials have attracted much attention due to their wide use in many application areas such as catalysis, hydrogen production, gas sensing and electrodes in fuel cells [1,2,3]. In microelectronics, CeO2 has been considered a high κ-gate oxide candidate since its moderate band gap (3–3.6 eV), high dielectric constant (κ: 23–26) and high dielectric strength (∼2.6 MV cm−1) [4]. CeO2 is also suitable for Si MOS devices due to its small lattice mismatch with Si and low interface-state density ( 1011 cm-2eV-1) [5]. For catalytic applications CeO2 has to be grown on metallic substrates, but few studies exist on cerium oxide film deposited on metals and most of them have the aim to depict the epitaxial growth [6 and references therein]. CeO2 deposition is achieved by using a variety of growth techniques [7, 8, 9,10]. When highly stoichiometric oxide is required, atomic layer deposition (ALD) is the most suitable technique. ALD is a self-limiting technique where thin films deposition can be performed at lower temperatures than other vacuum deposition techniques such as pulsed laser deposition or CVD, and the process condition guarantee low thermal budget, no or limited interdiffusion phenomena, and the possibility to use temperature-sensitive substrates. ALD deposition of CeO2 on Si or Si/SiO2 substrates has been explored by using different precursors [11,12,13,14], obtaining asdeposited films with polycrystalline structure [12,13], which ultimately influences the dielectric behavior [14]. However, ALD of CeO2 on metal substrates has not been explored yet. In this
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