Low Temperature Metal Organic Chemical Vapor Deposition of Aluminum Oxide Thin Films for Advanced CMOS Gate Dielectric Applications

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) 2,4-pentanedionate] and H2O. Chemical and microstructural properties of films grown in a temperature range of 250-450°C 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.