Study On Material And Properties Of Metal Nanocrystalline Memory

Non-volatile flash memory has been widely applied in smart phones and other mobile digital products and has rapidly developed in recent years. However, traditional polysilicon floating-gate memory cannot meet the industry demand for ultra-high storage density because of its inherent shortcomings. Therefore, the development of new generation of non-volatile memory is urgently needed. Based on the discrete charge storage concept in combination with new materials and advanced process technology, this thesis studied the performance of metal-insulator-semiconductor (MIS) and thin-film transistor (TFT) device structures for memory applications, and some achievements were obtained as follows:By means of the atomic layer deposition technique, platinum nanocrystals was deposited under300℃on the surface of Al2O3dielectric layer. The impact on the size and density of the nanocrystals by different reaction cycles has been researched in this article. AFM pictures showed that, in the non-film-forming situation, with the increase of cycle numbers, the volume of nanocrystals became larger and the density reduced. Then, by inserting the growth of in-situ ALD deposited HfO2on the embedded self-assembled monolayer/double layer platinum nanocrystals, we studied the relation between annealing temperature and HfO2crystallization degree. It shows that the introduction of platinum nanocrystals can effectively inhibit the growth of HfO2grains.The memory performance of the MIS structure with Ru nanocrystals has been investigated. The electrical characteristics of different compositional HfAlO dielectrics in the heterogeneous charge trapping layer have also been compared. The results showed that the heterogeneous charge-trapping layer capacitor can achieve memory characteristics much better than the single Ru nanocrystal layer. In addition, the memory performance is gradually improved with increasing the HfO2content of the charge-trapping layer. Therefore, the superior performances are obtained when using Ru nanocrystals/HfO2dielectric as a heterogeneous charge trapping layer, i.e., the C-V hysteresis window is12.6V for the scanning voltage range of±9V, and a memory window of about4.5V was achieved under+/-9V/100ms programming/erasing conditions, and a ten-year memory window was extrapolated to be3.4V at room temperature.The impact of deposition conditions and post-annealing conditions on the characteristics of sputtered In-Ga-Zn-O (IGZO) films has been studied. Then, the IGZO channel-based thin film transistor (TFT) memory devices with the gate stack of Al2O3/platinum nanocrystals (Pt-NCs)/Al2O3were fabricated, exhibiting good electrically programmable and UV-erasable characteristics. The programming of10V/100ms caused a threshold voltage shift of6.31V, and a5s UV erase led to a threshold voltage shift of4.04V.