Investigation of the programming accuracy of a double-verify ISPP algorithm for nanoscale NAND Flash memories

Abstract

This paper presents a detailed investigation of the performance of a double-verify algorithm for accurate programming of deca-nanometer NAND Flash memories. In order to minimize the programmed threshold-voltage distribution width in presence of discrete and statistical electron injection, a weakened programming step is applied to cells if their threshold voltage falls between a low- and a high-program-verify level during incremental step pulse programming. Clear improvements are shown with respect to the single-verify case, with minimal burdens on programming time and complexity.