Comparative Study of Titanium Dioxide Atomic Layer Deposition on Silicon Dioxide and Hydrogen-Terminated Silicon

Atomic layer deposition (ALD) of amorphous titanium dioxide (TiO 2 ) at 100 °C using the precursors titanium tetrachloride (TiCl 4 ) and water (H 2 O) was studied on two different surfaces by in situ X-ray photoelectron spectroscopy (XPS). The initial growth rate on hydroxyl-enriched silicon dioxide (SiO 2 ) is found to be higher than on hydrogen-terminated silicon. Moreover, the data show that the growth rate is accelerated during the first several ALD cycles on both surfaces. The interface between the SiO 2 substrate and TiO 2 is abrupt and composed of Si−O−Ti bonds. On the hydrogen-terminated silicon surface, the XPS results provide evidence of direct Si−Ti bond formation without traces of interfacial oxide. However, a silicon oxide layer forms on this surface after vacuum annealing, concurrent with the reduction of TiO 2, suggesting that the TiO 2 film is the oxygen source for the silicon oxidation under these conditions. Chlorine incorporates into the TiO 2 films on both surfaces and is found to concentrate near the Si/TiO 2 interface.