The plasma oxidation of titanium thin films to form dielectric layers

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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.