Atomic-layer deposition of TiO2 thin films with a thermally stable (CpMe5) Ti(OMe)(3) precursor

Abstract

Atomic layer deposition (ALD) of TiO2 films from (CpMe5)Ti(OMe)(3) as precursor and O-3 as co-reactant was examined. The high thermal stability of (CpMe5)Ti(OMe)(3) enabled ALD reaction up to a high temperature of 345 degrees C. A wide temperature window from 182 to 345 degrees C was achieved in the ALD process, and the growth per cycle increased with increasing the temperature from 0.025 to 0.06 nm/cycle in the ALD window. The impurity content of the films decreased with increasing growth temperature. Above 291 degrees C, the carbon content in the films decreased to the level in a single crystalline Si substrate. The morphology with patterns spreading radially from the multiple points developed above 236 degrees C, and the size of the grains decreased as the growth temperature increased. Eventually, a uniform morphology with fine grains was obtained at temperatures > 300 degrees C. The films grown at the high temperatures exhibited superior dielectric properties. Other common metalorganic precursors of Ti usually restrict the use of high-temperature ALD because they are thermally unstable and decompose below 300 degrees C. Therefore, (CpMe5)Ti(OMe)(3) is favorable for forming dense and high-purity TiO2 films by ALD.