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Macroscopic and microscopic electrical characterizations of high-k ZrO 2 and ZrO2/Al2O3/ZrO2 metal-insulator-metal structures

: Martin, D.; Grube, M.; Weinreich, W.; Müller, J.; Wilde, L.; Erben, E.; Weber, W.M.; Heitmann, J.; Schröder, U.; Mikolajick, T.; Riechert, H.


Journal of vacuum science and technology B. Microelectronics and nanometer structures 29 (2011), No.1, pp.01AC021-01AC028
ISSN: 0734-211X
ISSN: 1071-1023
ISSN: 2166-2746
ISSN: 2166-2754
Journal Article
Fraunhofer CNT ()

In order for sub-10 nm thin films of ZrO2 to have a dielectric constant larger than 30 they need to be crystalline. This is done by either depositing the layer at higher temperatures or by a postdeposition annealing step. Both methods induce high leakage currents in ZrO2 based dielectrics. In order to understand the leakage a thickness series of ultrathin ZrO2 and nanolaminate ZrO2 / Al2 O3 / ZrO2 (ZAZ) films, deposited by atomic layer deposition, was investigated. After deposition these films were subjected to different rapid thermal annealing (RTA) processes. Grazing incidence x-ray diffraction and transmission electron microscopy yield that the crystallization of ZrO 2 during deposition is dependent on film thickness and on the presence of an Al2 O3 sublayer. Moreover, the incorporation of Al2 O3 prevents crystallites from spanning across the entire film during RTA. C-V and I-V spectroscopies show that after a 650 °C RTA in N2 the capacitance equivalent oxide thickne ss of 10 nm ZAZ films is reduced to 1.0 nm while maintaining low leakage currents of 3.2× 10-8 A/ cm2 at 1 V. Conductive atomic force microscopy studies yield that currents are not associated with significant morphological features in amorphous layers. However, after crystallization, the currents at crystallite grain boundaries are increased in ZrO2 and ZAZ films.