Microstructure, wettability, optical and electrical properties of HfO2 thin films: Effect of oxygen partial pressure

• Sputtering-derived HfO2 coatings with different O2/Ar flow ratio have been deposited on Si(100) substrates.
• XRD measurements have shown that the as-deposited HfO2 thin films are all polycrystalline with monoclinic phase.
• Blue shift in band gap and reduction in refractive index have been detected with the increase of the O2/Ar flow ratio.

The effect of oxygen partial pressure on the microstructure, wettability, optical and electrical properties of sputtering-derived HfO2 thin films has been systematically investigated by using x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscope (AFM), UV–visible spectroscopy (UV–Vis), spectroscopy ellipsometry (SE), and electrical measurements. XRD results have shown that the HfO2 thin films are all polycrystalline with monoclinic phase. Based on analysis from FTIR, a strong absorption peak centered at 1105 cm−1 has been detected, indicating the formation of the interfacial layer. Reduction in particle size and decrease in root mean square (RMS) roughness of the HfO2 thin films have been detected by SEM and AFM measurements with the increase in oxygen partial pressure. Meanwhile, the contact angle decreases and the wettability increases with increasing the oxygen partial pressure. Combined with UV–vis and SE, the optical function of HfO2 thin films as functions of oxygen partial pressure has been determined. By means of electrical measurements, evolution of electrical performance of MOS capacitor based on HfO2 gate dielectrics related with oxygen partial pressure has been investigated systematically.

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