Improvement of the storage ability of Si-rich oxide layer in poly-Si based nonvolatile memory devices by implementation of taguchi method

摘要

The storage ability of silicon-rich silicon oxide (Si-rich SiOx) floating gates plays a critical role in poly-Si nonvolatile memory devices. In this study, the Taguchi method, a statistical means of experimental design which allows for the optimization of the storage characteristics with a dramatic reduction in the number of experiments by approximately 90%, is used. The memory window of the metal insulator semiconductor devices is used as a figure of merit to find out the optimal process parameters. Furthermore, the analysis of variance showed that the substrate temperature is the dominant factor affecting the memory characteristics of the SiO(x )storage layers. A significant improvement in the performance of poly-Si nonvolatile memory devices using the optimal Si-rich SiOx as a charge storage layer was observed. These devices show retention of the threshold voltage shift exceeding similar to 98% after 10(4)s and similar to 96% after 10 years extrapolation with programming/erasing voltages of -12 V/+11 V at a low duration of 1 mu s. Therefore, the poly-Si based nonvolatile memory devices using Si-rich SiOx as a storage layer show a high potential for memory system applications.