Electrical Screening Method of VNAND Flash Channel Hole Bending Defects

Abstract

A novel electrical screening method of channel hole bending (ChB) defects is proposed for the implementation of high-density vertical NAND (VNAND) flash memory. The ChB defects induces the leakage current between the two adjacent channel holes, which leads to fatal failure in storage systems. Thus, it is one of the key requirements for VNAND mass production to screen ChB defects electrically in advance. In the proposed screening method, a 3D checkerboard (CKBD) pattern is introduced, which consists of alternating programed (‘0’) and inhibited (‘1’) memory cells in a diagonal and horizontal direction. By measuring the leakage current between the channel holes, ChB defects can be successfully detected electrically.