Performance Improvement of SONOS Device as UV Total Dose Nonvolatile Sensor with Bottom-silicon-rich and Top-nitrogen-rich Nitride Structure

Silicon-silicon dioxide-silicon nitride-silicon dioxide-silicon (SONOS) capacitor devices with a bottom-silicon-rich and top-nitrogen-rich nitride bilayer stacked trapping layer (hereafter, SBNT-SONOS) have potential applications in UV total dose (TD) nonvolatile sensors. UV radiation induces a significant increase in the threshold voltage V-T of SBNT-SONOS UV TD nonvolatile sensors. Experimental results indicate that the UV-induced increase in the V-T of the SBNT-SONOS capacitor device under a positive gate voltage (PGV) is nearly 3 V after UV irradiation at 100 mW.s/cm(2) TD. The change in the V-T of the SBNT-SONOS capacitor after UV irradiation is also dependent on UV TD of up to 100 mW.s/cm(2). The charge-retention loss of the nonvolatile SBNT-SONOS capacitor after 10-year retention is below 10%. The UV TD information can be permanently stored and accumulated in nonvolatile SBNT-SONOS capacitor devices. Devices with a single standard nitride layer as the trapping layer show lower performance and poor reliability as UV TD sensors. Devices with a bottom-silicon-rich and top-nitrogen-rich nitride bilayer trapping layer show higher performance and better reliability as UV TD sensors than devices with a single standard nitride layer. The SBNT-SONOS capacitor device used in this study has demonstrated the feasibility of nonvolatile UV TD sensing.