Suppression of inhibit cell Vth disturbance in three dimensional stack NAND flash memory

J Nanosci Nanotechnol. 2013 Sep;13(9):6382-8. doi: 10.1166/jnn.2013.7623.

Abstract

In this work, we characterize inhibit cell Vth disturbance related to the 3D stack NAND channel boosting during program and propose a new method to suppress the hot carrier injection related disturbance. The hot-carrier effect on program inhibit string is arisen from the potential difference between the highly boosted channel and turned-off bit line (BL) selection device which is directly connected to the boosted channel. In the proposed method by us, electrons are flown to the channel with the edge word line (WL) biased initially at a Vpass before channel cut-off. Then the highly boosted channel potential decreases to some extent due to the re-distribution of excess electrons after channel cut-off. Consequently, when we apply the proposed method, large disturbed cell Vth in the inhibit strings for high Vpass is well controlled by suppressing hot-carrier generation, which leads to the higher pass voltage during both program and read operations while keeping reliable cell operations for 3D stack NAND.