Atomic layer deposition of metal oxide thin films

This work summarizes preparation of replacement materials for silicon dioxide in microelectronic applications such as the gate insulator in transistors and the insulating layer in the capacitor of memory elements. Hafnium and zirconium oxides are leading candidates for this application. Atomic layer deposition (ALD) was the method used to prepare thin films of several dielectric materials including hafnium and zirconium oxide. In the atomic layer deposition process, highly uniform and conformal coatings are made by the alternating exposures of a surface to vapors of two reactants. Reactors were constructed for testing potential precursors and deposition processes. Several methods of precursor volatilization and delivery into the reactor were studied and optimized.; Using metal alkyl amide precursors and water, films of pure hafnium and zirconium oxide were prepared and characterized. The reactivity of these precursors was investigated using a quartz crystal mass balance, which gave insight into the deposition mechanism, the precursor's vapor pressure, and the minimum exposure required for surface saturation. Thin tantalum and aluminum oxide films were also prepared from metal amide precursors.; A theoretical model was constructed which related the observed surface roughness of the hafnium and zirconium oxide films at high deposition temperatures to the film crystallinity. This model correctly predicted alloying tantalum or aluminum oxide with the hafnium or zirconium oxide would inhibit the film's crystallinity and thus produce smoother films. A theoretical model was also constructed for producing highly conformal films using reactive precursors such as metal amides. This model correctly predicted the minimum exposure that was required to produce completely conformal films over both flat surfaces and deep trenches or holes.; Silicates of both hafnium and zirconium oxides were prepared by substituting a silanol precursor molecule for the water used to prepare the previously mentioned metal oxides. These films showed higher than expected growth rates. When this silanol precursor was used with an aluminum amide precursor a growth rate over thirty times higher than the highest previously observed ALD growth rate was observed. A catalytic polymerization mechanism was proposed to explain this unusual result.