Electrical properties of HfO2 charge trap flash memory with SiO2/HfO2/Al2O3 engineered tunnel layer

The program/erase (P/E) characteristic of tunnel barrier engineered charge trap flash (TBE-CTF) memory with MAHOS (Metal/Al2O3/HfO2/SiO2/Si) structure and MAHAHOS (Metal/Al2O3/HfO2/Al2O3/HfO2/SiO2/Si) structure were investigated. The tunnel barrier structures for nonvolatile memory (NVM) application were designed by using the quantum–mechanical tunnel model (QM) and then the CTF memory devices were fabricated by stacking various dielectric materials for tunnel barrier, charge trap layer and blocking layer. As a result, a faster P/E speed and a longer data retention time were obtained from the MAHAHOS memory device. Especially, the program speed was enhanced by 104 times from 100 ms to 10 us, and the erase speed was enhanced by 102 times from 1 s to 10 ms. Also, the MAHAHOS device showed an improved retention characteristic compared with the MAHOS device. In addition, it is found that a high work function gate electrode (Pt) contributes to a significant reduction of data erasing time and an improved data retention characteristic of MAHAHOS memory device.