Atomic Layer Deposition of Titanium Dioxide Thin Films from Cp*Ti(OMe)₃ and Ozone

Abstract

The thermal atomic layer deposition of TiO2 from Cp*Ti(OMe)3 and ozone was studied in a 300 mm wafer reactor by quadrupole mass spectrometry (QMS). The deposited thin films were analyzed by X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), grazing incident X-ray diffraction, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The XRR and XPS measurements revealed that nearly stoichiometric TiO2 films were grown in a self-limiting growth mode. The growth per cycle increased from 0.22 Å at 235 °C to 0.29 Å at 330 °C. Films deposited on titanium nitride showed an anatase crystal structure, while films deposited on ruthenium crystallized in the rutile phase. The ToF-SIMS analysis indicated that the carbon contamination reduced to very low levels at a deposition temperature of 295 °C. The QMS studies revealed the release of MeOH during the precursor pulse. CO2 and H2O were released during the ozone pulse at a process pressure of 7 mbar. At a pressure of 3 × 10−3 mbar, the release of the Cp* ligand and the remaining OMe ligands during the ozone pulse could be observed. It was demonstrated that QMS studies can be used in a 300 mm reactor at very low pressures to study the process chemistry.