Study of gate-injection operated SONOS-type devices using the gate-sensing and channel-sensing (GSCS) method

SONOS devices using gate injection programming and erasing have better cycling endurance because the gate oxide is not stressed by P/E operations. This work studies the gate injection behavior in detail using the recently developed gate-sensing and channel-sensing (GSCS) technique. GSCS accurately locates the charge centroid during programming/erasing and reliability tests. For the first time, we can track the charge centroid for gate-injection ldquotop BE-SONOSrdquo and various SONOS-type devices. Our results indicate that the charge centroid after electron gate injection is close to the nitride center, irrespective of various nitride thickness and top dielectric. Moreover, there is electron and hole vertical mismatch after hole gate injection. Comparing the results from SONS, we can clearly prove that electrons are mainly distributed inside the bulk nitride instead of the interfaces between oxide and nitride. For SNOS and SNS, where there is electron and hole injection simultaneously, two-region approximation can give us more detailed information about electron and hole capture. By comparing experimental data with theoretical modeling, we have shown that nitride 7 nm or thicker captures all the injected electrons up to total charge area density ~10¹³ cm^-2.