Structural and Optical Properties of HfO2 Films on Sapphire Annealed in O2 Ambient

The structural properties of HfO₂ films could be improved by thermal treatment owing to their crystallization. We deposited HfO₂ films on sapphire by radio frequency (RF) magnetron sputtering, whose base vacuum pressure was lower than 4.5 × 10 −6 ㎩, RF power was 100 W, working temperature was 200°C, working pressure was 3 mTorr, and the density of the active gas (Argon) was 20 sccm. After depositing the HfO₂ films, the samples were thermally treated by rapid thermal annealing (RTA) in O₂ ambient at different temperatures. Subsequently, the measured physical properties (structural, morphological, and optical) indicated that the crystallite size, refractive index at a wavelength of 632 ㎚, and packing density increased with rising temperatures. In particular, an HfO₂ film thermally treated at 800℃ in O₂ ambient had the highest refractive index of 2.0237 and packing density of 0.9638. The relation between optical and structural properties was also analyzed.