Characterization of reliability in 3-D NAND flash memory

The trap density (N_t) in nitride storage layer is extracted in 3-D NAND flash memory cells with tube-type poly-Si body. We extract the N_t by utilizing AC-g_m method and deriving related equations in cylindrical coordinate. The AC-g_m method makes the N_t profiling with distance from the interface possible. We also characterize the behavior of transient bit-line current (I_BL) during reading after applying a pre-bias (V_pre). Depending on the dominance of charge trapping in blocking dielectric or at the interface between the tunneling oxide and poly-Si body, different behaviors of transient I_BL are observed. To identify the cause, we systematically analyze the capture and emission of charges in different trap sites by investigating the behavior of transient I_BL during reading with various V_pres.