New Source/Drain Hot Carrier Injection Disturbance of NAND Flash Devices

A fully calibrated 3-D simulation of a NAND flash string is used to characterize the source/drain hot carrier disturbance phenomenon for the first time. Through the word line 31 (WL31) program voltage (Vpgm) disturbances simulation with various pass voltage (Vpass) for other word lines, we conclude that the source/drain hot carrier injection contributes to an abnormal Vpgm disturbance not only at a 14-V Vpass, but also at 4-V Vpass condition. Instead of the well-known FN programming disturbance due to insufficient boosting potential at low Vpass, the GIDL-induced electron-hole pair generation at the source side (WL30) of WL31 and electron injection into the Vpgm-biased WL31 are the dominant mechanisms of the WL31 Vpgm disturbance in the ‘01’ state cell string at a 4-V Vpass condition. This hot carrier disturbance phenomenon is similar to that of the 14-V Vpass condition, even though it occurs on the drain side (SSL) of WL31.