Low Temperature Metal Organic Chemical Vapor Deposition of Aluminum Oxide Thin Films for Advanced CMOS Gate Dielectric A
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Low Temperature Metal Organic Chemical Vapor Deposition of Aluminum Oxide Thin Films for Advanced CMOS Gate Dielectric Applications Spyridon Skordas, Filippos Papadatos, Zubin Patel, Guillermo Nuesca, Eric Eisenbraun, Evgeni Gusev1, and Alain E. Kaloyeros. University at Albany Institute for Materials, School of Nanoscience and Nanoengineering, Albany, NY 12203, U.S.A. 1 IBM, T. J. Watson Research Center, P. O. Box 218, Yorktown Heights, NY 10598, U.S.A. ABSTRACT A low-temperature metal organic chemical vapor deposition (MOCVD) process for the growth of aluminum oxide for gate dielectric applications has been developed. Amorphous films were deposited on 200-mm Si(100) wafers, employing an Al β-diketonate precursor [Al(III) 2,4pentanedionate] and H2O. Chemical and microstructural properties of films grown in a temperature range of 250-450oC were studied using x-ray photo-electron spectroscopy (XPS), xray diffraction (XRD), Rutherford back-scattering spectrometry (RBS), nuclear reaction analysis (NRA), cross–sectional (X) scanning and transmission electron microscopy (XSEM and XTEM). A design of experiment (DOE) method was used for process mapping and optimization. An optimized process window was defined for the growth of dense, amorphous films with carbon and hydrogen inclusion as low as 1 at. % and 3 at. % respectively. Post-deposition annealing studies indicated that chemical and structural film properties are generally stable up to 650°C. The electrical performance of the films was evaluated by capacitance-voltage (C-V) and currentvoltage (I-V) measurements on metal-oxide-semiconductor (MOS) structures. The dielectric constant (k) obtained was 6.7-9.6 (depending on annealing conditions), with equivalent oxide thickness (EOT) as low as 1.3 nm. Leakage current densities lower than that of equivalent SiO2 films were also achieved. INTRODUCTION As allowable SiO2 thickness shrinks, the semiconductor industry is facing the replacement of SiO2-based gate dielectrics owing to leakage current-related reliability issues. High dielectric constant(k) insulators, which allow thicker layers while maintaining equivalent capacitance, are a solution1. Many materials are under consideration, especially those possessing amorphous microstructures, good thermal and chemical stability, high band-gap and breakdown field, and compatibility with potential integration scenarios1. Al2O3 offers these characteristics, as well as low permeability of alkali and other impurities2,3,4. In previous studies, Al2O3 films were grown via various CVD and physical vapor deposition (PVD) methods5,6. Low temperature CVD is attractive since potential issues such as ion-induced damage to substrates and undesirable thermal strain are avoided. MOCVD methods for Al2O3 growth have been reported, with various precursors including Al β-diketonates, such as Al(III) 2,4pentanedionate [Al(acac)3], due to their desirable properties7,8. These include stability in air, decomposition pathways in oxidizing ambient leading to contaminant-free oxide phases at low temperatur
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