Program Disturb Phenomenon by DIBL in MLC NAND Flash Device

We have investigated a new program disturb phenomenon by DIBL (drain-induced barrier lowering) in MLC NAND Flash device. It is found that lower programmed state cell shows large DIBL effect and its BVdss measurement results in unwanted programming of nearby erased state cells. It is attributed to punch-through leakage of programmed state cell during BVdss measurement. Electrons from this leakage are accelerated by high drain bias, which leads to hot carrier programming. The results indicate that excessive boosted channel potential by local self-boosting scheme creates 'DIBL induced program disturb' by punch-through of channel cut-off cell. This paper suggests that excessive boosted channel potential should be controlled in short channel device for high density MLC NAND Flash operation.