Modeling of Single Electron Charging in Nanocrystal Memories

Abstract

A three-dimensional model is proposed to describe single electron charging into the nanocrystals that compose the floating gate of a metal-oxide-semiconductor transistor. It is built on the physical and geometrical parameters of the device. If the nanocrystals have a cylindrical symmetry, the 3D approach can be analytically reduced to a 2D model. Different effects that play an important part on single electron charging, such as the electrostatic coupling between two nanocrystals and the doping density of the channel, are analysed. Moreover the necessity of including the excited states of the nanocrystals and the subbands of the channel is shown. Finally the tunneling times to charge the nanocrystals in the floating gate from the channel are simulated and discussed.

Indexing terms:

• Floating gate
• Memory
• Nanocrystal
• Tunneling
• Electrostatic coupling
• Simulation