Microstructure and electrical properties of CeO_2 ultra-thin films for MFIS FeRAM applications

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 CeO2 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.

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 CeO2 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 （△ VVB） ranging from 0.015 V to 0.12 V and the density of trapped charges ranging from 1.45×10^11 to 3.01×10^11 cm^-2. A leakage current of 4.75×10^-8 -9.0~×10^-7 A/cm^2 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.