Regensburg 2010 – scientific programme
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DS: Fachverband Dünne Schichten
DS 9: Poster: Synthesis of Nanostructured Films by Self-organization, Thermoelectric Thin Films and Nanostructures, High-k and Low-k Dielectrics, Layer Deposition Processes, Layer Growth, Layer Properties, Application of Thin Films, Surface Modification, Hard and Superhard Coatings, Metal Layers
DS 9.31: Poster
Monday, March 22, 2010, 15:00–17:30, Poster D1
Spectroscopic Ellipsometry Investigation of Ultrathin Nb2O5 and Nb2O5/Al2O3 Layers — Marion Friedrich1, Yue Huang2, Yan Xu2, Shi-Jin Ding2, Li Ding1, Ovidiu Gordan1, and •Dietrich R. T. Zahn1 — 1Semiconductor Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany — 2State Key Laboratory of ASIC and System, Department of Microelectronics, Fudan University, Shanghai 200433, China
Since amorphous Nb2O5 films have unique properties, they are widely used as optical interference filters, O2 sensors and electrochromic material. Also, there is considerable interest in using it as a high permittivity dielectric to replace gate insulators and integrated capacitors. The high k/low k combination of Nb2O5/Al2O3 is a good candidate to implement the "VARIOT" concept in nonvolatile memory devices.
Single Nb2O5 layers and Nb2O5/Al2O3 double layers on silicon were characterised by variable angle spectroscopic ellipsometry in the spectral range from 0.74 eV to 5 eV and by means of vacuum ultraviolet ellipsometry up to 9.8 eV at 67.5∘ angle of incidence at the synchrotron source BESSY. For the Nb2O5 layers the thickness and optical constants were determined. Furthermore, the influence of annealing on the optical properties and the band gap was investigated.
All samples were prepared by atomic layer deposition on HF cleaned silicon substrates at 300∘C. The precursors for Nb2O5 and Al2O3 are Nb(OEt)5 and Al(CH3)3, together with H2O, respectively. The base pressure was 2.3× 102 Pa. Post-deposition annealing was performed in N2 ambient for 30 seconds at temperatures between 500∘C and 800∘C.