A Process-Aware Compact Model for GIDL-Assisted Erase Optimization of 3-D V-NAND Flash Memory

Abstract

This article presents the accurate compact modeling methodology to optimize the gate-induced drain leakage (GIDL)-assisted erase operation for vertical stack-up, multiple stack, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> -directional shrink of the 3-D vertically integrated NAND (V-NAND) flash memory. The artificial neural network (ANN) is initially applied in the V-NAND transistors to describe the various GIDL characteristics with channel profile variations. In addition, physics-based <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> network models are investigated to accurately model the complex process in the state-of-the-art V-NAND products. All models are implemented in Verilog-A, and the time dynamics of the GIDL-assisted channel potential increase for erase operations are successfully reproduced in the SPICE simulations. This SPICE-compatible compact model is essential to the design technology co-optimization (DTCO) for over 200-layer V-NAND, because the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> delay-related erase failures have become an important issue in the high aspect ratio (HAR) channel holes. Based on the proposed compact model, the highly accurate GIDL-assisted erase simulations are performed, and an erase optimization procedure is demonstrated with GIDL injection level, physical etch limit, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> shrink rate in the next V-NAND candidate structures. Therefore, this process-aware compact model is a valuable tool for pathfinding activities in the early stage of 3-D V-NAND flash memory development.