Modulation of the structural and optical properties of sputtering-derived HfO2 films by deposition power

• HfO2 gate dielectrics were deposited on Si and quartz substrate by sputtering.
• The as-deposited HfO2 films are monoclinic phase, regardless of deposition power.
• Red shift in band gap and increase in refractive index have been detected.

High-k gate dielectric HfO2 thin films have been deposited on Si and quartz substrate by radio frequency magnetron sputtering. The structural and optical properties of HfO2 thin films related to deposition power are investigated by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), ultraviolet–visible spectroscopy (UV–Vis), and spectroscopic ellipsometry (SE). Results confirmed by XRD have shown that the as-deposited HfO2 thin films are not amorphous state but in monoclinic phase, regardless of deposition power. Analysis from FTIR indicates that an interfacial layer has been formed between the Si substrate and the HfO2 thin film during deposition. AFM measurements illustrate that the root mean square (RMS) of the as-deposited HfO2 thin films’ surface demonstrates an apparent reduction with the increase of deposition. Combined with UV–Vis and SE measurements, it can be noted reduction in band gap with an increase in power has been observed. Additionally, increase in refractive index (n) has been confirmed by SE.