Berlin 2008 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 13: Dielectric and ferroelectric thin films and nanostructures III
DF 13.7: Vortrag
Donnerstag, 28. Februar 2008, 16:00–16:20, EB 107
Investigation of (SrO)x(ZrO2)(1−x) high-k dielectrics deposited by molecular beam deposition — •Matthias Grube1, Oliver Bierwagen2, Dominik Martin1, Lutz Geelhaar2, and Henning Riechert2 — 1namlab gGmbh, D-01187 Dresden — 2Qimonda, D-81730 Munich
Thin high-k dielectrics will be essential for metal-insulator-metal capacitors in future dynamic random access memory. Focused on this necessity, we investigated thin amorphous films of ZrO2 and (SrO)x(ZrO2)(1−x) grown by molecular beam deposition. As substrates, we used n++-Si-wafers which were covered with a pre-deposited 5 nm-thin TiN layer. Current-voltage and capacitance-voltage measurements were performed to determine the electrical properties of the dielectrics.
The ZrO2 films were grown by three different methods, either in ultra-high vacuum or with an additional supply of O2, and employing either Zr or ZrO targets. A k-value of 23 - 28 was extracted from a thickness-series, which is consistent with the value for amorphous ZrO2.
(SrO)x(ZrO2)(1−x) was grown by co-evaporating SrO and ZrO2. For as-grown films with x ≈ 0.6, a k-value of about 6 was extracted. This is significantly lower than the tabulated value. Preliminary experiments for x ≈ 0.4 indicate a more reasonable value of k ≈ 20. In addition, post-deposition annealing experiments were performed, which improved the properties of the films. Their density was increased, and their capacitance equivalent thickness was reduced to 50% and less.