Chemical Vapor Deposition of TixSi1-xO2 Films: Precursor Chemistry Impacts Films Composition

Thin films of composition TixSi1–xO2 were grown by low‐pressure (LP) CVD on silicon (100) substrates using tetraethyl orthosilicate (TEOS), [Si(OC2H5)4], and either titanium isopropoxide (TTIP), [Ti(O‐iPr)4], or anhydrous titanium tetranitrate (TN), [Ti(NO3)4], as the sources of SiO2 and TiO2, respectively. The substrate temperature was varied between 300 °C and 535 °C, and the individual precursor delivery rates ranged from 5 sccm to 100 sccm. Under these conditions, growth rates ranging from 0.6 nm min–1 to 90.0 nm min–1 were observed. As‐deposited films were amorphous to X‐rays, and cross‐sectional transmission electron microscopy (TEM) images showed no compositional inhomogeneity. Rutherford backscattering (RBS) spectrometry revealed that the relative concentration of TiO2 and SiO2 was dependent upon the choice of TiO2 precursor. Possible multi‐precursor deposition scenarios are presented and discussed in relation to the observed variation of film stoichiometry. For the TTIP–TEOS pair, the systematic variation of Ti content with deposition conditions could be accounted for by a growth scenario that limits SiO2 growth to TiO2 sites within the composite film. For the case of TN–TEOS the Ti content remained close to 50 % for all conditions studied. A specific chemical reaction between TN and TEOS prior to film deposition accounts for the observed composition. Thin films of TixSi1–xO2 are deposited on Si(100) at 300 to 535°C by LPCVD using TEOS (tetraethyl orthosilicate) and either TTIP (titanium tetra isopropoxide) or TN (anhydrous titanium(IV) nitrate). Deposited films are shown to be amorphous with TiO2/SiO2 ratio dependent on the choice of titanium precursor. In the TN–TEOS system, the titanium content remains close to 50% for all conditions studied. However, in the TTIP–TEOS system, systematic variation of titanium content with deposition conditions can be explained by a growth scenario that limits SiO2 growth to TiO2 sites within the composite film.