Deposition and characterization of HfO₂ thin films

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Virginia Tech

Hafnium Dioxide(HfO₂) thin films were deposited on glass, metal, and silicon wafer substrates using magnetron RF reactive sputtering techniques. Structure and morphology of the thin films were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results revealed that the sputtered HfO₂ thin films were (111) preferred oriented with single crystalline or polycrystalline natures. The sputtering parameters, including gas flow ratios of Ar/O₂, substrate temperature, pressure, and RF power levels, were examined, and their effects on the thin film structure and properties are discussed. Transparent hafnium oxide thin films can be deposited only when the RF power is lower than a certain level, which is limited by the gas flow ratio of Ar/O₂. High substrate temperature is critical for high (111) orientation in thin films while a high gas flow ratio of Ar/O₂ is important for crystal structure and adhesion. Annealing in oxygen atmosphere following the deposition was also found to be effective in improving thin film adhesion and resistance of losing adhesion during thermal cycles. Refractive index, and electrical resistance measurements show that HfO₂ thin films deposited by RF reactive sputtering under optimized conditions have promising electrical and optical properties which deserve further study.