A new technique for measuring threshold voltage distribution in flash EEPROM devices

A new, simple test circuit for evaluating the reliability of flash EEPROM devices is described. It measures threshold voltage (V/sub th/) distributions of a large number of cell transistors with easy static operation similar to I-V curve measurement. Moreover, each cell transistor in a large array is selectable to measure static characteristics. This circuit makes it possible to measure the V/sub th/ distribution even in the negative region after erase operation for a NAND-type EEPROM.