Study On Charge Trapping Memory With MAHOS Structure

Flash memory has great share in current non-volatile semiconductor memory market, because it has several advantages, such as:high density, low power, small size, good reliability, and so on. However, with the microelectronics technology nodes moving forward, the traditional flash memory which was based on floating gate concept has encountered serious challenge in scaling, especially reaching 45nm and 32nm technology node. Under this circumstance, discrete charge storage technology will push the current flash technology to more advanced technology. There are three methods for discrete charge storage technology:the first is introducing nano-crystals; the second is utilizing compound materials that have deep energy level defects itself, i.e. charge trapping memory; the third is utilizing the mixture of nano-crystal and charge trapping materials as charge storage points. This work mainly focuses on charge trapping memory which has good electrical characteristics. Compared with the traditional floating gate memory, charge trapping memory has smaller current leakage with local leakage access of tunneling layer.In this article, research background of flash memory is introduced firstly, including the origin, the application and market, the status and development trend of flash memory. At the same time, the structure, wok principle of the device, and some general memory performance parameters are also introduced.Secondly, in order to alleviate the problem of the scaling of the traditional flash memory, we studied the charge trapping memory which employs the method of discrete charge storage. Simultaneity, the research of the trapping layer of the charge trapping memory was summarized and analyzed. There are several improved methods of the trapping layer, including high-k dielectric materials trapping layer, the oxygen-doped amorphous silicon nitride oxide trapping layer, implanted nano-crystal trapping layer and the stacked structure of the trapping layer. We also discussed the further research trends of the charge trapping memory.Finally, we prepared the device with the structure of Al,Pt/Al2O3/HfO2 SiO2/Si using high-k materials and high work function metal. The formula confirmed that the Al2O3 as blocking layer is superior compared with traditional SiO2 as blocking layer. We investigated and analyzed the charge storage performances and retention characteristics of the prepared quasi-MOS capacitor. The performance of devices with different dielectric thickness and different gate electrode were also compared. The experiment results indicate that:HfO2 as blocking layer has larger memory window (excellent charging characteristics); tunneling layer thickness can influence flat-band voltage shift; the device with Pt gate electrode has smaller current leakage and better retention than Al electrode.