CGST CIRCUIT OF NON-VOLATILE MEMORY AND TESTING METHOD THEREOF

摘要

PURPOSE: A CGST(charge gain stress test) circuit of non-volatile memory and its testing method are provided not to impose on a peripheral circuit and to optimize a testing time by controlling a value of stress voltage. CONSTITUTION: A sense amplifier(20) outputs a compared result(SOUT) by comparing a reference current and a cell current. The output signal(SOUT) of sense amplifier(20) is able to become a logical 1 or to become a logical 0 according to a design of circuit. Therefore, the sense amplifier(20) outputs the logical 0 because the cell current is smaller than reference current if an early threshold voltage of flash memory cell(30) is larger than a ground source voltage. A data of flash memory cell(30) is erased by setting the reference current at high, feeding a second erase voltage to a source of flash memory cell(30) with a third switch, feeding a first erase voltage to a gate of flash memory cell with a second switch and floating a drain. The erase and a read operations are repeated until the cell current flowed in the flash memory cell(30) flowed higher than the reference current. The size of reference current is decided according to a maximum size of voltage fed to a stress. A characteristic of flash memory cell(30) is evaluated by using the sense amplifier(20) after feeding a stress voltage for a regular time.