Atomic layer deposition of TiO2 from TiCl4 and O3

Atomic layer deposition (ALD) of thin films from TiCl4 and O3 on Si(100) substrates was investigated. The growth of TiO2 was obtained at substrate temperatures of 225-600 °C from these hydrogen-free precursors. Formation of anatase phase in the films was observed at 250-600 °C. In addition, the rutile phase was revealed in thicker films deposited at 600 °C. Compared to the well studied TiCl4-H2O ALD process the TiCl4-O3 process allowed higher growth rate at 275-600 °C. In addition, relatively low surface roughness was obtained for thicker (> 50 nm) films of the anatase structure deposited from TiCl4 and O3 at 350-400 °C. Therefore TiCl4 and O3 appeared to be a good precursor combination for ALD of TiO2, particularly for applications that require low concentration of hydrogen contamination.