Phase Sequences in Processing
PZT and SBT exist in several different phases. When PZT films are deposited under normal conditions the phase that is formed has the pyrochlore structure. These pyrochlores are generally ferroelectric but only at cryogenic temperatures; thus, they are not useful for room temperature ferroelectric memory devices. The pyrochlores deposited by sputtering, sol—gel spin-on, or other techniques are subsequently subjected to an annealing cycle, either in a furnace (typically an hour at 650°C) or via RTA (Rapid Thermal Annealing), typically for 90 seconds to a maximum temperature of about 800°C. These heat treatments result in 100% of the material being converted to the ferroelectric perovskite phase. Usually this heating process is carried out in an oxygen atmosphere to prevent oxygen loss from the film. The lowest temperature at which 100% of the film has been successfully converted to perovskite is 450°C . Recently it has been suggested  that the pyrochlore phase is stabilized by Pb4+ ions in PZT, and efforts are underway to reduce this Pb4+ concentration to see if even lower temperature conversion to the perovskite phase is possible.
KeywordsPhase Sequence Fluorite Structure Furnace Anneal Pyrochlore Structure EXAFS Data
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- 334.Wersing W., Siemens Corp., Eur. Conf. Polar Devices (Bled, Slovenia, 1996);Google Scholar
- 336.Rodriguez M. A., Boyle T. J., et al., Proc. ISIF 1996Google Scholar
- 338.Rae D., Thompson J. G., and Withers R. L., Acta Cryst. B48, 418 (1992);Google Scholar
- 342a.pure SBN has also been studied by Yi J. H. et al., J. Phys. IV France 8, 225 (1998)Google Scholar
- 343.Kapitza P., Proc. Roy. Soc. (London) A119, 428 (1928) 344.Google Scholar
- 343a.Bussem W., Gross F., and Hermann K., Ann. Phys. 64, 537 (1930)Google Scholar
- 346.Van Itterbeck A. and de Bock A., Ann. Phys. 11, 635 (1945)Google Scholar
- 349.Heine V., Proc. Phys. Soc. A69, 513 (1956)Google Scholar
- 350.Colombani A. and Huet P., Structure and Properties of Thin Films, eds. Neugebauer C. A., Newkirk J. B., and Vermilyea D. A. (Wiley, New York, 1959) p.253Google Scholar
- 351.Buckel W., Ibid., p.53Google Scholar