Study on Formation of Ge Nanocrystal using SiGeO and SiGeN layer for Nonvolatile Memory Applications
| Autor: | Yen-Ting Hsieh, 謝彥廷 |
|---|---|
| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 In recent years, the portable electronic products have widely applied, such as digit camera, laptop, cell phone and so on. These portable electronic products play an important role in the market, and these products are all based on the nonvolatile memory (NVM) for data storage center. Hence, the current requirements of NVM are the high density cells, low-power consumption, high-speed operation and good reliability for scaling down devices. However, all of the charges stored in the conventional floating gate NVM will leak back to substrate because the tunnel oxides have leakage paths during operation processes. It is even worse when being scaled down. Therefore, the thickness of tunnel oxide is difficult to scale down in terms of charge retention and endurance characteristics. The nonvolatile nanocrystal memory and SONOS memory are promising candidates to replace the conventional floating gate memory, because the discrete storage nodes of themselves are enveloped. Both of them are capable to improve data retention under operation and have been provided by the endurance test which is good for device further down scaling efficiently. In this thesis, we proposed a SiGeO stacking structure serving as Ge nanocrystals self-assembled layer for application of nanocrystal NVM. We successfully incorporated oxygen into SiGe layer to form SiGeO ternary film by sputtering commixed SixGe1-x target in an Ar/O2 ambiance at room temperature. In additional we fond out that pre-annealing-capping oxide (PACO) is a critical step in our experimental process, and then we used the different oxidized mechanism between Si and Ge. The uniform and high density (~1012cm-2) of Ge nanocrystals was fabricated after a rapid thermal annealing (RTA) process. The Ge nanocrystals were isolated better and the defects (leakage path) in the SiOx which surrounds the nanocrystal were reduced by increasing the thermal treatment time. This process can reduce the probability of charges losing and improve the data retention time. As the same, we used similar method that oxygen was replaced by nitrogen. The Ge nanocrystals embedded in SiNx structure was fabricated by using the same process. The memory window for the stacked structure with Ge NCs embedded in SiNx layer is larger than Ge NCs embedded in SiOx layer, due to the extra charge trapping centers generated for Ge NCs embedded SiNx layer. Furthermore, we also increased the time for thermal treatment resulting in better Ge NCs isolation and less defects in the SiNx. That improves the data retention time, too. In addition, by using high dielectric constant layer (ErSiGeO) for charging tapping layer structure has better memory ability and the operation speed is improved, too. Finally, all of the above fabrication techniques for the application of nonvolatile nanocrystal memory can be compatible with current manufacture process of the integrated circuit manufacture. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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