Germanium Nanoparticle Formation into Thin SiO2 Films by Negative Ion Implantation and Their Electric Characteristics

Germanium nanoparticles in a thin SiO2 film on Si have been formed by negative ion implantation for the development of very low power consumption electron devices using nanoparticles. Their electrical properties of 25-nm-SiO2/Si films including Ge nanoparticles were investigated with CV method after subsequent annealing at various temperatures. Ge atoms were implanted at 10 keV with fluencies of 1X1015 and 5X1015 ions/cm2. Samples were annealed at 300, 500, 700 and 900 deg C for 1 h. Depth profiles of implanted Ge atoms in the SiO2 films were measured by using a high-resolution RBS technique. The formed Ge nanoparticles were studied by cross-sectional TEM observation. After annealing at less than 700 deg C, Ge nanoparticles were confirmed in the film. After 300 deg C-annealing, a CV curve had so small hysteresis that could not be applied to memory devices. After 500 deg C-annealing, both samples with 1X1015 ions/cm2 and with 5X1015 ions/cm2 had obvious hysteresis curves. Calculations of charge and nanoparticle intensity from flat band shift and implanted Ge dose lead about one electron in one nanoparticle with 3nm diameter. These results suggest that thin SiO2 films including Ge nanoparticles formed with negative ion implantation can applied with memory devices.