Performance Evaluation of the MOHOS Flash Memory with Fluorinated HfO2 Charge Storage Layer Using Gate Fluorine Ion Implantation

Abstract

Electrical characteristics improvement of the fluorinated metal/SiO2/HfO2/SiO2/Si (MOHOS) flash memory using gate fluorine ion implantation (GFI) process has been investigated. Si-F or Hf-F bonds formation due to fluorine incorporation can reduce undesirable charges trapping and leakage path creation in the tunneling oxide, which consequently increases the program/erase (P/E) speed and endurance. Moreover, fluorinated flash memory not only enhances P/E efficiency, but also improves the data retention characteristic, which can be explained by more deep-level traps and reduced leakage path due to fluorine incorporation. P/E window closure during endurance stressing is significantly suppressed for the fluorinated flash memory, which can be also ascribed to stronger Si-F or Hf-F bonds formation within the dielectrics due to fluorine incorporation. However, the fluorinated MOHOS flash memory clearly exhibits apparent erase-saturation phenomenon due to higher electric field across on blocking oxide. The results clearly indicate the fluorinated flash memory using GFI process to simultaneously fabricate fluorinated OHO dielectrics becomes a feasible technology for future MOHOS-type nonvolatile flash memory application.