The plasma oxidation of titanium thin films to form dielectric layers

Abstract

A remote indicatively coupled radio frequency plasma has been used to oxidize titanium thin films evaporated onto silicon substartes. The substrate was heated during oxidation to temperatures between 200 and 500 °C using a resistively heated furance. Titanium dioxide layers were formed of thicknesses from 53 to 150 nm. The crystal structure was shown to be rutile by x-ray diffraction for oxidation temperatures of 500 °C. These samples were also seen to have a thin interfacial silicon dioxide layer. Measurements on 1-mm Al dot capacitors showed the leakage current of a 53-nm film oxidized at 500 °C to be below 10−8 A at a 2-V bias. Good capacitance-voltage characteristics were observed for high oxidation temperatures, with a dielectric constant of between 15 and 22 for the TiO2/SiO2 layers. The refractive index of the layers was measured by ellipsometry to be 2.5–2.6. Plasma oxidation thus provides a low-temperature method of forming titanium dixoide thin films.