C-V characteristics of metal-titanium dioxide-silicon capacitors

Titanium dioxide capacitors were fabricated on silicon wafers using electron-beam evaporation. The TiO2 films varied in thickness from 500 to 2000 Å. Post-deposition oxidation at 1000°C in dry O2 was used to promote stoichiometric conversion of the films to the rutile phase. Capacitive densities of greater than 2 pf/sq. mil were obtained (dielectric constants ranged from 4 to 40). For long oxidation times, significant silicon dioxide grows under the TiO2 as a result of oxygen diffusing through the TiO2 film. Titanium was also shown to diffuse into the silicon during the oxidation cycle resulting in an n-type diffusion. Surface state densities ranging from 1011 to 5 × 1011 cm−2 eV−1 at midgap were obtained for good devices. Longer oxidation times result in lower capacitance, leakage current and surface state density.