Plasma enhanced chemical vapor deposition of TiO₂ in microwave‐radio frequency hybrid plasma reactor

A plasma tool and accompanying process have been developed for plasma enhanced chemical vapor deposition of TiO₂ thin films for dynamic random access memory application. The microwave‐rf (radio frequency) hybrid reactor consists of microwave power (2.45 GHz) for electron cyclotron resonance, a hollow cathode (0.1–30 MHz) for control of the plasma potential, and an additional rf (13.56 MHz) power to the substrate electrode for ion extraction and ion energy control. X‐ray diffraction showed the anatase phase at a low deposition temperature below 400 °C, but the rutile phase dominanted above 400 °C. Low energy ion bombardment densifies the TiO₂ films and suppresses rutile formation. A dielectric constant of 60(±5) at 1 MHz was obtained, independent of film thickness in a range from 20 to 200 nm. A SiO₂ buffer layer was found to be important in order to prevent silicide formation and to keep the leakage current below 10⁻¹⁰ A/cm².