Extraction of Interface Trap Density in the Region Between Adjacent Wordlines in NAND Flash Memory Strings

A new method to extract the interface trap density (N_it) on the surface of the Si region between adjacent wordlines (WLs-called space region) in NAND flash devices is presented in this letter. The N_it is successfully extracted by applying charge pumping (CP) method, TCAD simulation, and modified equations. The CP current I_CP of single WL and electrically tied two WLs are measured using fixed-base CP measurement as a function of pass bias. In addition, an effective space area for CP is extracted by TCAD simulation, and the equation, which is used to extract N_it, is modified to extract separated N_its in the channel and the space regions. We confirm that our method is accurate by comparing the measured I_CP with the calculated one.