Metal-organic chemical vapor deposition of high-k dielectric Ce-Al-O layers from various metal-organic precursors for metal-insulator-metal capacitor applications

The possibilities to grow thin layers of high-k dielectric CeAlO3 by pulsed injection metal-organic chemical vapor deposition using different metal-organic (MO) precursors have been investigated. Three pairs of MO precursors were studied for the growth of the films: Ce (IV) and Al(III) 2,2,6,6-tetramethylheptane-3,5-dionates, Ce tetrakis(1-methoxy-2-methyl-2-propoxide)-diethylaluminumethoxide and tris(isopropylcyclopentadienyl)cerium-tris(diethylamino)aluminum. Under optimized conditions, all three pairs of investigated precursors enabled the growth of close to stoichiometric Ce-Al-O films at reasonably low temperatures, 400-450 °C, however, crystalline CeAlO3 phase was not present in as-deposited layers. Films were grown on Si(100) and Si(100)/TiN substrates. Two kinds of TiN electrodes were used - amorphous TiN (15-30 nm thick) and crystalline TiN (70-100 nm thick) layers, grown by chemical vapor deposition and physical vapor deposition techniques, respectively. The pure tetragonal CeAlO3 phase was crystallized in films by a short annealing in Ar or N2 at 800-850 °C. Required annealing conditions (temperature and annealing duration) depended on the selected precursors and substrates. Thermomechanical degradation of Si/TiN/Ce-Al-O structures was observed by Scaning Electron Microscopy after the annealing of the samples. Lower degradation degree was observed for structures with a thin amorphous TiN layer.