Experimental Characterization of the Vertical Position of the Trapped Charge in Si Nitride-Based Nonvolatile Memory Cells

We present a broad set of experiments on silicon nitride-based memories aimed at the investigation of the vertical position of the charge trapped in the nitride layer of silicon-oxide-nitride-oxide-semiconductor (SONOS) memories during program and erase in the tunneling regime. The results obtained for SONOS devices with conventional oxide-nitride-oxide and oxide-nitride-oxide-nitride-oxide gate stacks, as well as with high-top dielectric, have been validated by comparing different characterization techniques. It has been shown that, for SONOS cells, the charge centroid is located in the center of the silicon nitride layer, and its position is quite insensitive to the program or erase conditions and to the gate-stack composition.