Trap Profiling in Nitride Storage Layer in 3-D NAND Flash Memory Using Retention Characteristics and AC- $\text{g}_{\mathrm {m}}$ Method

The trap density ( $N_{t}$ ) in nitride storage layer of 3-D NAND flash memory cells with tube-type channel structure is extracted. To extract $N_{t}$ profile in the nitride layer, retention characteristics, and ac-transconductance ( $\text{g}_{\rm m}$ ) method are used, and equations are derived in cylindrical coordinate. The $N_{t}$ profile at $E_{C}- E_{T}$ smaller than 1 eV is extracted using retention characteristics of the cells measured at high temperature. The peak value of extracted $N_{t}$ is $\sim 1 \times 10^{\mathbf {19}}$ cm $^{\mathbf {-3}}$ eV $^{\mathbf {-1}}$ at a $E_{C}-E_{T}$ of 0.93 eV. AC- $g_{\rm m}$ method is used to profile the $N_{t}$ in $ E_{C}-E_{T}$ higher than 1 eV. Extracted $N_{t}$ profile shows a reasonable continuity between both approaches and looks like a Gaussian function.