Non-volatile memory (NVM) retention improvement utilizing protective electrical shield

摘要

An electrical shield is provided in a non-volatile memory (NVM) cell structure to protect the cell's floating gate from any influence resulting from charge redistribution in the vicinity of the floating gate during a programming operation. The shield may be created from the second polysilicon layer or other conductive material covering the floating gate. The shield may be grounded. Alternately, it may be connected to the cell's control gate electrode resulting in better coupling between the floating gate and the control gate. It is not necessary that the shield cover the floating gate completely, the necessary protective effect is achieved if the coupling to the dielectric layers surrounding the floating gate is reduced.