Insulating properties of tantalum pentoxide capacitor films obtained by annealing in dry ozone

Highly insulating tantalum pentoxide (Ta2O5) capacitor films were obtained by dry O-3 annealing at low temperatures ranging from 350 to 500 degrees C. Typical leakage current density and resistivity of a 10-nm-thick Ta2O5 film measured at 2 MV/cm were 2.5x10(-8) A/cm(2) and 4.8x10(13) Ohm cm, respectively, obtained by dry O-3 annealing at 450 degrees C, while leakage current density of the as-deposited film was about 10(-1) A/cm(2). It was confirmed that the mechanism which improves the insulating properties after dry O3 annealing involves the reduction of the leakage current due to the reduction of the concentration of such impurities as hydrogen and carbon, and the reduction of oxygen vacancies in Ta2O5 films. In addition, amorphous Ta2O5 films annealed in dry O-3 show much better insulating properties than polycrystalline films. This can be attributed to the suppression of leakage current at the grain boundaries. Regarding dielectric properties, Ta2O5 films have an average dielectric constant of 28, and the typical SiO2 equivalent thickness of a 10-nm-thick Ta2O5 film was 2.4 nm. Results of the time dependent dielectric breakdown measurement, the calculation of the storage node height of a capacitor, and the frequency dependence of the capacitance value suggest that the above Ta2O5 film is applicable to an integrated capacitor for next generation devices, replacing conventional capacitor films. (C) 1999 American Institute of Physics. [S0021-8979(99)07103-0].