Memory characteristics of cobalt-silicide nanocrystals embedded in HfO_2 gate oxide for nonvolatile nanocrystal flash devices

摘要

Cobalt-silicide (CoSi_2) nanocrystals (NCs) were investigated for use in charge storage for metal oxide semiconductor (MOS) devices with thin HfO_2 tunneling and control oxide layers. CoSi_2 NCs were synthesized by exposure of Co/Si/HfO_2 tunneling oxide/Si stacks to an external UV laser. Observations from transmission electron microscopy and x-ray photoelectron spectroscopy clearly confirm the formation of CoSi_2 NCs and the values of Co-Si bonding energies that are shifted 0.3 eV from original values, respectively. The CoSi_2 NCs in MOS devices exhibited a large memory window of 3.4 V as well as efficient programming/erasing speeds, good retention, and endurance times.