Investigation of PECVD TiO₂ on Silicon

Patrick R. McCurdy, Laura Sturgess, Sandeep Kohli, and Ellen R. Fisher

Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872

Continuous wave (CW) and equivalently powered, pulsed radio frequency plasmas were used to deposit thin films (~100 Å) of titanium dioxide on to Si(100) substrates. In these experiments oxygen plasmas were created by feeding oxygen gas through the coil region, titanium (IV) isopropoxide was introduced downstream from the plasma region. These films have been characterized using XRD, XPS, SEM and AES. XRD showed that TiO₂ films deposited at substrate temperatures ³350ºC are polycrystalline with an anatase structure, while at lower substrate temperatures the films were amorphous. Results show high quality films were produced with some carbon incorporation. Annealing these films in vacuum showed the TiO₂/Si interfacial region to be stable to 850^oC. At 900^oC the TiO₂ began to be reduced to Ti₂O₃, presumably while Si was oxidized to SiO_x. Upon annealing at a 950^oC further reduction of the TiO₂ film was noted to include TiO. The 950^oC film would partially re-oxide upon exposure to atmosphere. XRD of annealed films showed no crystalline structure. SEM of the TiO₂ film surfaces showed the as deposited films were smooth and structureless and remained so even when annealed at 850^oC. Annealing at 950^oC caused the surface to become very rough, resulting in the rupturing of the TiO₂ surface thus exposing areas of the underlying Si substrate.