The thermal stability, and microstructure of zirconium aluminum oxide (ZAO) and hafnium aluminum oxide (HAO) mixed oxides were evaluated. The films were prepared by chemical solution deposition (CSD) using a solution prepared from zirconium, or hafnium butoxyethoxide, and aluminum butoxyethoxide dissolved in butoxyethanol. The films were spun onto SiOxNy coated Si wafers and furnace annealed at temperatures from 500-1200 o C in oxygen for 30 minutes. The microstructure and electrical properties of ZAO and HAO films were examined as a function of Zr/Al and Hf/Al ratio and annealing temperature. The films were characterized by X-ray diffraction, FTIR, RBS and AES. Crystallization/phase separation of ZrO2 and HfO2 in ZAO and HAO films was observed to be concentration and annealing temperature dependent. At low (<25%) ZrO2 or HfO2 concentrations at anneal temperatures less than 900 o C, an amorphous g-alumina like material was observed in the ZAO and HAO films. Phase partitioning of the ZAO and HAO films was observed at higher ZrO2 or HfO2 concentrations and at higher anneal temperatures. Addition of Al2O3 to ZrO2 or HfO2 was found to increase the crystallization temperature of tetraganol ZrO2, enable the formation of the tetragonal HfO2 phase and increase the annealing temperature at which transformation of the tetragonal to monoclinic phase of ZrO2 or HfO2 is observed. Transformation from the tetragonal to the monoclinic phase was observed to occur more readily at lower temperatures in HAO films than ZAO films. Evidence of enhanced oxygen conduction at elevated temperatures was observed for 90% Hf 10% Al mixed oxide films.
By: Deborah Neumayer, Eduard Cartier
Published in: RC22292 in 2002
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