Microstructure and electrical properties of CeO2 ultra-thin films for MFIS FeRAM applications

Abstract: A detailed investigation about the dependence of microstructure and electrical properties on annealing temperature was carried out for cerium oxide(CeO2) ultra-thin films (18 nm to 110 nm) on n-type Si(100) substrates by RF magnetron sputtering. Substrate temperature was kept constant at 400 for all samples. The as ℃-deposited films were subsequently annealed in air ambient at 700, 800 and 900 for 1 h respectively. The crystallinity and surface morphology of the CeO ℃ 2 films were analyzed with X-ray diffractometer(XRD), scanning electron microscope(SEM), atomic force microscope(AFM) and Raman scattering measurement. Electrical properties of the Au/CeO2/Si/Au structure were examined by high frequency capacitance—voltage (C—V) characteristics at 1 MHz and leakage current density—electric field (J—E) characteristics. A Raman peak of the CeO2 thin films was seen at 463 cm−1. From C—V data, these films exhibit dielectric constants ranging from 18 to 23, the hysteresis width (∆VFB) ranging from 0.015 V to 0.12 V and the density of trapped charges ranging from 1.45×1011 to 3.01×1011 cm−2. A leakage current of 4.75×10−8 −9.0×10−7 A/cm2 at 2 MV/cm was observed. The experimental results show that the CeO2 buffer layers are suitable for non-volatile metal-ferroelectric-insulator-semiconductor(MFIS) structure field-effect-transistors(FETs) memory applications. Key words: CeO2 thin film; RF magnetron sputtering; microstructure and electrical properties; MFISFETs memory application