Characteristics of HfO2-Al2O3 Gate insulator films for thin Film Transistors by Pulsed Laser Deposition

Hafnium oxide-aluminum oxide (HfO2-Al2O3) dielectric films have been fabricated by Pulsed Laser Deposition (PLD), and their properties are studied in comparison with HfO2 films. As a gate dielectric of the TFT, in spite of its high dielectric constant, HfO2 has a small energy band gap and microcrystalline structure with rough surface characteristics. When fabricated by the device, it has the drawback of generating a high leakage current. In this study, the HfAlO films was obtained by Pulsed Laser Deposition with HfO2-Al2O3 target(chemical composition of (HfO2)86wt%(Al2O3)14wt%). The characteristics of the thin Film have been investigated by x-ray diffraction (XRD), atomic force microscopy (AFM) and spectroscopic ellipsometer (SE) analyses. The X-ray diffraction studies confirmed that the HfAlO has amorphous structure. The RMS value can be compared to the surface roughness via AFM analysis, it showed HfAlO thin Film has more lower properties than HfO2. The energy band gap (Eg) deduced by spectroscopic ellipsometer was increased. HfAlO films was expected to improved the interface quality between channel and gate insulator. Apply to an oxide thin Film Transistors, HfAlO may help improve the properties of device.