Extraction of Spatial Trap Profile in Nitride of the 3D NAND Flash Memory Using Re-Program method

Abstract

A fast charge loss phenomenon in three-dimensional (3D) NAND flash memory is crucial to improving retention characteristics. It is caused by de-trapping in shallow traps in the charge trap layer (CTL) after the program. The Re-PGM method is proposed to mitigate the fast charge loss, where it performs the re-programming to maintain the same PV level after the initial PGM. During the interval time (tint), the trapped density in shallow traps decreases. To further improve the Re-PGM method and profile the CTL trap distribution, we propose a Re-Program (Re-PGM) with a counter-pulse (CP) scheme. Also, the CP bias condition is determined to minimize the disturbance of adjacent cells. Furthermore, the spatial trap profile is extracted by substituting ∆Vth using the Re-PGM method into the trap extraction equation. The higher trap distribution is observed at the BE-TOX/CTL interface, indicating the formation of additional defects due to dangling bonds formed by oxygen atoms in the BE-TOX.