New accurate method to analyze both floating gate charge and tunnel oxide trapped charge profile in NAND flash memory

New method to extract the amount of floating (FG) charge (Q_FG) apart from oxide trapped charge (Qox) generated by program and erase (P/E) cycles is proposed, for the first time. Q_FG shift by P/E cycling shows asymmetry between programmed and erased states as follows; Q_FG exhibits the peak at ~100 cycles in programmed state, while Q_FG monotonically reduces in erased state. Next, the midgap voltage (Vmid) shift of the cell caused by the generation of Q_ox is also extracted by this method. Therefore, it enables to analyze the profiles of the hole and electron-trap separately across the oxide in detail. It is demonstrated that the hole-trap is mainly distributed near to Si surface and the centroid of electron-trap is located near to the middle of oxide. In addition, it is found that hole-trap near to Si has strong dependence on erase bias.