Temperature Effects on Charge Storage and Transfer of Nanocrystalline CdSe Embedded Zr-Doped HfO2 MOS Memory Device

Abstract

The influence of temperature on the charge storage and transfer characteristics of the nanocrystalline CdSe embedded Zr-doped HfO2 high-k dielectric on the p-type Si wafer has been studied. With the increase of temperature, the hole-trapping capacity is increased but the electron-trapping follows the opposite trend, which results in a small reduction of the memory window. From the frequency dispersion measurement result, at high temperatures, holes are loosely trapped at the nanocrystal/high-k interface and electrons are mainly trapped in the bulk nanocrystal. The high temperature induces a larger leakage current because it enhances the charge supply and transfer in the high-k stack. At the low applied voltage, the charge transfer follows the Schottky emission mechanism. In the high, positive gate voltage region, charges are transferred following the Poole-Frenkel mechanism at the low temperature and the Fowler-Nordheim mechanism at the high temperature. The temperature has little effect on the sample's leakage current-gate voltage hysteresis due to the large charge trapping capability. In summary, temperature is an important factor in the operation of the nanocrystals embedded high-k memory device because it affects the charge storage and transfer mechanisms.