Growth of Zr Substituted Barium Titanate Thin Films from the Vapor Phase
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U12.2.1
Growth of Zr Substituted Barium Titanate Thin Films from the Vapor Phase R. Ganster, S. Hoffmann-Eifert, and R. Waser Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany
ABSTRACT We report on the growth of Ba(Ti1-xZrx)O3 thin films on Pt(111) / TiO2 / SiO2 / Si substrates by means of metal-organic chemical vapor deposition (MOCVD) using liquid precursors. The MOCVD system consists of an AIXTRON AIX-200 horizontal reactor with a TriJet® vaporizer. In the multi-source injection system the different single element precursor solutions were introduced separately in a pulse mode. The focus of our investigations lies on the correlation between processing conditions, growth rate, and film properties, namely stoichiometry, crystal structure, and surface morphology. Dense, polycrystalline Ba(Ti0.63Zr0.37)O3 films were successfully grown on platinum coated silicon substrates at temperatures around 630°C. INTRODUCTION Charge storage in state-of-the-art integration devices with scales in the nanometer regime proves to be a real challenge and requires an appropriate synthesis approach.1 Metal-organic chemical vapor deposition (MOCVD) is a promising technology fulfilling the needs of ever smaller two and three-dimensional systems with characteristic spatial lengths of several ten nanometers and a vertical thickness in the nanometer region.2 Most of the research on high-k material systems deposited by MOCVD for evaluation in charge storage and high frequency devices is focused on the solid solution (BaxSr1-x)TiO3, mostly in the composition x=0.7. Due to this industrially forced restriction a large potential of other interesting materials has not been made use of so far. To explore prospects in a wider spectrum of thin film dielectric materials we looked closer at the possibility of B site substitution. Another auspicious candidate is the solid solution system Ba(Ti1-xZrx)O3 (BTZ) which is well established in the large area of ceramic passive components, i.e. as a base material for MLCCs (multi layer ceramic capacitors).3 Ba(Ti1-xZrx)O3 thin films deposited by means of chemical solution deposition (CSD) already showed promising electrical properties, which puts the material into a competitive position to comply with the necessities for integrated capacitor structures.5 Still a drawback is the fact that the CSD technique is not compatible with state-of-the-art integration scales. Another approach reported recently used a sputtering technique.6 Here we report on the growth of Ba(Ti1-xZrx)O3 (x ≈ 0.35) thin films on Pt(111) / TiO2 / SiO2 / Si substrates by an MOCVD technique utilizing a multi-source liquid delivery system.
U12.2.2
EXPERIMENTAL The first part deals with the specific features of the MOCVD system. In the second part we describe the used precursors and substrates, the BTZ film deposition process, and the utilized analytical techniques. MOCVD system The experimental setup consists of an AIXTRON ‘AIX 200’ horizontal reactor designed for small wafer sizes mostly with an area of 1’’
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