Effect of Post Metallization Annealing for La 2 O 3 Thin Film

esults. The second is the time when the annealing process is performed.This one also seems to be consistent because larger VFB shift toward negativeside than as-deposited sample was also observed in PDA sample in myresults. The third is the time when the aluminum upper electrodes areevaporated on the rare earth oxides thin films. It is well known thataluminum has the property of the strong affinity with oxygen and thisproperty worked on this result. In other words, aluminum inhales theoxygen in rare earth oxides at a moment aluminum cone into contact withrare earth oxides thin films. This assumption also seems to be reasonablebecause the value of VFB shift in the case of aluminum upper electrodes waslarger than the one in the case of platinum upper electrodes.O O AluminumSilicon SubstrateLn 2O 4+ or Ln 2O2+2 Ln 2O2+2 Ln 2O 4+Ln 2 O 4+ or Ln 2 O2+2 Silicon SubstrateO O O OLn 2 O 4+ or Ln 2 O2+2 Silicon SubstrateDeposition ProcessAnnealing ProcessContact with AluminumFigure 4-2: Schematic illustrations of oxygen vacancies mechanismThen, the reason why VFB shift toward negative side recovered byPMA with aluminum must be made clear. There are also two possibilitieshere. One is the effect of covering surface of rare earth oxides films beforethe annealing process. That seems to prevent oxygen from getting away tooutside. However, this assumption is leaving one question. If thisassumption is correct, PMA with all kind of metal upper electrodes issupposed to have an effect on the suppression of VFB shift toward negativeside. Actually, however, PMA with gold upper electrodes did not only yield- 95 -