Transparent Multi-Level NAND Flash Memory and Circuits Based on ZnO Thin Film Transistor

Abstract

A simple compatible process is developed to fabricate NAND flash memory and driving logic circuits simultaneously based on atomic layer deposition zinc oxide thin film transistors (ZnO TFTs), in which the active layer and the floating gate layer both are ZnO thin films. The flash memory exhibits excellent memory properties, including large memory window (9.8 V), long retention performance and even multi-level data (2 bits) writing and reading ability. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}\times {4}$ </tex-math></inline-formula> NAND flash array is designed and tested to verify its storage function. A novel modulated enhancement/flash (E/F) inverter is proposed and used on the logic circuits. Finally, a fully transparent flash system with NAND memory cell and driving logic circuits is realized successfully, which has great potential for application of 3D integrated circuits, transparent or flexible electronics.