Macroscopic and microscopic electrical characterizations of high-k ZrO 2 and ZrO 2 /Al 2 O 3 /ZrO 2 metal-insulator-metal structures Dominik Martin a and Matthias Grube Namlab gGmbH, 01187 Dresden, Germany Wenke Weinreich, Johannes Müller, and Lutz Wilde Fraunhofer CNT, 01099 Dresden, Germany Elke Erben, Walter M. Weber, Johannes Heitmann, b and Uwe Schröder b Namlab gGmbH, 01187 Dresden, Germany Thomas Mikolajick Namlab gGmbH, 01187 Dresden, Germany and Chair of Nanoelectronic Materials, 01062 Dresden, Germany Henning Riechert Paul-Drude-Institut für Festkörperelektronik, 10117 Berlin, Germany Received 11 August 2010; accepted 8 November 2010; published 14 January 2011 In order for sub-10 nm thin films of ZrO 2 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 ZrO 2 based dielectrics. In order to understand the leakage a thickness series of ultrathin ZrO 2 and nanolaminate ZrO 2 / Al 2 O 3 / ZrO 2 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 Al 2 O 3 sublayer. Moreover, the incorporation of Al 2 O 3 prevents crystallites from spanning across the entire film during RTA. C-V and I-V spectroscopies show that after a 650 °C RTA in N 2 the capacitance equivalent oxide thickness of 10 nm ZAZ films is reduced to 1.0 nm while maintaining low leakage currents of 3.2  10 -8 A / cm 2 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 ZrO 2 and ZAZ films. © 2011 American Vacuum Society. DOI: 10.1116/1.3523397 I. INTRODUCTION Future dynamic random access memory DRAM and logic technology nodes require insulating materials with high dielectric constants. These are very difficult to achieve with purely amorphous thin films since higher dielectric constants are obtained in crystalline phases. To achieve a k-value larger than 30 in thin ZrO 2 films it is necessary to obtain the tetrag- onal crystalline phase. This is done by either depositing the layer at high temperatures or by a postdeposition annealing step. Both methods induce high leakage currents. To reduce these small amounts of Al 2 O 3 can be incorporated in the center of a ZrO 2 film, forming a ZrO 2 / Al 2 O 3 / ZrO 2 ZAZ film. ZrO 2 films have been shown to fulfill the requirements of the 50 nm DRAM technology node. 1,2 Incorporation of very small amounts of Al 2 O 3 into ZrO 2 reduces leakage while maintaining a sufficiently high dielectric constant. 3–6 A deeper understanding of the mesoscopic mechanisms in- volved is essential for future materials engineering. This work is a comparative study of thickness series of ultrathin ZrO 2 and ZAZ films, deposited by atomic layer deposition ALD carried out in order to gain a deeper understanding of leakage mechanisms and the effect of Al incorporation in ultrathin dielectric films. After deposition these films were subjected to different rapid thermal annealing RTA pro- cesses and characterized by grazing incidence x-ray diffrac- tion GIXRD, x-ray reflectometry XRR, transmission elec- tron microscopy TEM, I-V and C-V spectroscopies, and a Electronic mail: martin@namlab.com b Formerly with Qimonda Dresden GmbH & Co OHG, 01099 Dresden, Germany. TABLE I. List of sample and deposition parameters. For simplicity, films are addressed by their target thickness. The cycle sequence was TEMAZ for ZrO 2 and TEMAZ/TMA/TEMAZ for ZAZ. The oxygen precursor was ozone and the deposition temperature was 270 ° C. Name Material Target thickness nm Cycle sequence Z6 ZrO 2 6 64 Z8 ZrO 2 8 86 Z10 ZrO 2 10 110 ZAZ6 ZAZ 6 32/2/28 ZAZ8 ZAZ 8 42/2/41 ZAZ10 ZAZ 10 53/2/53 01AC02-1 01AC02-1 J. Vac. Sci. Technol. B 29„1…, Jan/Feb 2011 1071-1023/2011/29„1…/01AC02/8/$30.00 ©2011 American Vacuum Society Author complimentary copy. Redistribution subject to AIP license or copyright, see http://jvb.aip.org/jvb/copyright.jsp