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MOCVD of SrTa2O6 Thin Films for High-k Applications

  • Stephan Regnery (a1) (a2), Reji Thomas (a1), Hans Haselier (a1), Peter Ehrhart (a1), Rainer Waser (a1), Peer Lehnen (a2), Stefan Miedl (a2) and Markus Schumacher (a2)...

Abstract

SrTa2O6 thin films with thickness between 6 and 150nm were deposited in a multi-wafer planetary MOCVD reactor combined with a TRIJET® liquid delivery system using a single source precursor, strontium-tantalum-(methoxyethoxy)-ethoxide dissolved in toluene. A rather narrow process window for the deposition of stoichiometric SrTa2O6 was found for this precursor at low pressures and a susceptor temperature around 500°C. Films were grown on Pt/TiO2/SiO2/Si, TiNx/Si, and SiO2/Si substrates. The as-deposited films were X-ray amorphous and could be crystallized by post-annealing at a temperature ≥700°C. The SrTa2O6 phase was dominating within a broad range of compositions (Sr/Ta: 0.4–0.7) and a perovskite type phase was observed for Sr/Ta > 0.7. The electrical properties have been investigated with MIM and MIS capacitors after sputter deposition of Pt top electrodes. The amorphous films had a relative permittivity, ε, in the range of 25–45, and low leakage currents. Crystallized films were investigated with Pt MIM capacitors. For stoichiometric SrTa2O6 the dielectric permittivity reached values of ε = 100–110, but the leakage currents were increased. Remarkably, the permittivity is not very sensitive to deviations from the exact stoichiometry of the SrTa2O6 phase (Sr/Ta: 0.40.7), but a decrease to values of ε = 30–40 is observed along with the phase transition at high Sr contents.

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[1] Kingon, A.I., Maria, J.P., and Streiffer, S.K, Nature, 406, 1032 (2000)
[2] Rodriguez, M.A., Boyle, T.J., Hernandez, B.A., Talland, D.R., Vanheusden, K., J. Am. Ceram. Soc., 82, 2001 (1999)
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[7] International Centre for Diffraction Data, ICDD, powder diffraction files.

MOCVD of SrTa2O6 Thin Films for High-k Applications

  • Stephan Regnery (a1) (a2), Reji Thomas (a1), Hans Haselier (a1), Peter Ehrhart (a1), Rainer Waser (a1), Peer Lehnen (a2), Stefan Miedl (a2) and Markus Schumacher (a2)...

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