Structure and optical properties of HfO2 films on Si (100) substrates prepared by ALD at different temperatures

In this work, HfO2 thin films were deposited on Si (100) wafer by using reactive atomic layer deposition at different temperatures. By characterizing the Raman spectroscopy and XRD patterns, we find that with the substrate temperature increases, the structure of the film transforms continuously, and a substrate with sufficiently high temperature can generate enough energy to produce a film in the crystalline phase. UV-vis absorption spectrum shows that the anti-reflection effect of the deposited HfO2 thin films is effective. The characteristic reflective peak of the film exhibits a slightly blue shift with increasing the substrate temperature, indicating that the thickness of the film decreases as the substrate temperature increases. The refractive index of the visible to near infrared spectral range increases with the increase of temperature, and the film becomes more compact. The surface morphology of HfO2 films was measured by AFM, and the skewness, kurtosis and roughness of the films were also analysed. Increasing substrate temperature has led to improvement in the film uniformity and compactness. The above results indicate that the substrate temperature is a critical parameter in determining the film structure, morphology and optical properties.