Study On The Nonvolatile Nanocrystal Memory

Flash memory has been the dominant and mainstream devices in current non-volatile semiconductor memory market, since the the concept of Flash memory was proposed. Flash memory has now accounted for more than 90%of the non-volatile semiconductor memory market. While the Flash memory in the commercial application has been hugely successful, with the scaling of microelectronics technology, Flash memory, which is based on the traditional floating gate concept has encountered serious technical challenges due to the tradeoffs between the high speed, low power operation and long time retention. Higher requirement was proposed at the speed,power,and reliability.there are mainly two trends in searching for the next-generation non-volatile memory devices in industry and academe. One is the evolution way to push the current FLASH technology to more advanced technology node. The other is the revolution way to utilize totally different storage mechanisms when FLASH technology is approaching its physical limits. This work focus on the evolution ways to study the Nanocrystal floating gate non-volatile memory devices.As for the nanocrystal floating gate memory devices, we analyzed the ways to improve the device performances from the point of the device structure and the energy band. First, we established a charging and retention model for nanocrystal floating gate memories, we investigated the impact of nanocrystal materials, high-K tunneling dielectrics and the thickness of tunneling dielectric on the charging and retention performances. Our results indicated that metal nanocrystal memory devices have a better retention performance than semiconductor nanocrystal memory, and the charging characteristics and the charge retention performances were improved for the high-K tunneling dielectric. Next, we investigated the feasibility of e-beam evaporation combined with rapid thermal annealing process to fabricate metal nanocrystals. the Si/ZrO2/Au Ncs/SiO2/Al structure with Au nanocrystals embedded in the ZrO2 tunneling dielectric was fabricated. The charging characteristics and the charge retention performances were electrically investigated. The experimental results are consistent with the prediction of our model.