Process and device characteristics of self-assembled metal nano-crystal EEPROM

Abstract

Metal nanocrystals self-assembled on gate tunneling oxide can be used to replace the conventional Si/Ge nanocrystals as the floating gate in EEPROM cells. We have demonstrated the successful use of Au and W with their respective process dependence and self-assembly characteristics. The new material options can potentially enhance the applicability and functionality of the nanocrystal EEPROM device. Implications on process integration, in particular the control oxide growth and overall thermal budget, are examined by microscopy, gate current injection and channel mobility monitoring. Charging by hot-carrier injection and control gate tunneling have both been observed by shifts in I–V characteristics. The electrostatic behavior of metal nanocrystals is similar to that of Si nanocrystals in terms of the asymmetrical threshold voltage on source–drain reversal after hot-carrier injection and the Coulomb blockade effects. The electrodynamic behavior is expected to be quite different due to the density of states, but further study is required for quantitative analysis.