HfO2 nanoparticles embedded within a SOG-based oxide matrix as charge trapping layer for SOHOS-type memory applications

Abstract

In this work, HfO2 nanoparticles (np-HfO2) are embedded within an amorphous Spin-On Glass (SOG)-based oxide matrix and used as charge-trapping layer for memory applications. Following specific thermal treatments, the np-HfO2 act as charge storage nodes able to retain charge injected after applying a constant gate voltage. A Silicon-Oxide-High-k-Oxide-Silicon (SOHOS)-type memory has been fabricated with the high-k charge-trapping layer containing 5, 10 and 15% of np-HfO2 concentration within the SOG-oxide matrix. The memory's charge trapping characteristics are quantized by measuring the flat-band voltage (Vfb) shift of SOHOS capacitors after charge injection and then correlated to np-HfO2 concentration. Since a large memory window has been obtained for our SOHOS memory, the relatively easy injection/annihilation (programming/erasing) of charge injected through the substrate opens the possibility to use this material as an effective charge-trapping layer. A very small injected charge density of 1×10–6C/cm2 shifts Vfb by 100mV without needing to overstress the dielectric by hot-carrier injection, a usual method in SOHOS memories. In conclusion, using a simple spin-coating method for the charge-trapping layer, wide current memory windows have been obtained in SOHOS-memories and their charge-trapping characteristics are quantized and correlated to the np-HfO2. concentration.