含鎳/鎳鍺奈米點之氧化鍺非揮發性記憶體

Abstract

在非揮發性金屬記憶體的研究方面，本論文所選取的金屬量子點材料為鎳及鎳鍺化物。然而金屬的量子點記憶體在近年來受到矚目，其相對於傳統半導體材料用於量子點記憶體上，有諸多的優勢，其優勢包含低功率耗損、高密度的能階、沒有明顯的量子侷限效應(carrier confinement)、有效降低元件尺度、且可調變的空間大，因為隨不同的金屬有不同的功函數。除此之外，我們在選擇金屬的材料上，在線上製程中有其他的應用及良好的熱穩定度，是我們選擇鎳及鎳鍺化物的一個主要的原因。金屬鎳的高功函數能夠提供較深的位能井來捕獲電荷載子，此外，金屬鎳相較於其他高功函數的金屬(如:鉑)有較低的形成溫度，大約 600~650度，這對於結合高介電含數的材料是非常有幫助的，因為高介電材料大多在低溫結晶。

直接沉積、成核、氧化是最一般用來形成金屬鎳奈米點的方法。本研究主要探討:藉由鎳和鍺雙層的氧化作用可形成分散的鎳鍺/鎳的奈米點。而鎳和鎳鍺奈米點的形成呈現出很大的記憶體窗口。由低溫氧化矽鍺鎳堆疊結構明顯的臨界電壓漂移可判讀"0"和"1"的訊號，這在非揮發性記憶體是非常重要的。此外，本製程也使用低溫的電漿沉積的氧化矽。另外，本研究也探討奈米點被埋在氧化鍺介電層內的特性。然而，鎳和鍺在熱處理條件下的變化也將被探討。在鎳鍺矽的系統中將會於氮氣處理中形成鎳鍺化合物 。

We have studied experimentally and theoretically two kinds of nonvolatile metal nanocrystal memories: nickel nanocrystal memories and nickel- Germanide nanocrystal memories. The metal nanocrystals memories come into notice as so many advantages. The advantages of metal nanocrystals over their semiconductor counterparts include low power consumption, higher density of states, smaller energy perturbation due to carrier confinement, stronger coupling with the channel, better size scalability, and the design freedom of engineering the work functions to optimize device characteristics. The reasons why nickel/nickel- Germanide is chosen as the materials for the nanocrystals are the compatibility with current manufacturing technology of semiconductor industry.The high work function of Ni s 4.9 eV enables the creation of a deep potential well for the trapping of charge carriers. Furthermore, the NC formation temperature of Ni s,600 ~650°C is lower compared with other high work function metals such as Pt (900 °C). This is important for the integration of metal NCs with high-k material which is generally known to crystallize at low temperatures forming leakage current paths and diffusion paths for metals and other impurities The direct deposition, nucleation, and oxidation process were the popular method to form nickel nanocrystal nanocrystal. The nickel-germanium (NiGe) and nickel (Ni) nanocrystal formation by oxidizing double layer structure by nickel layer and germanium layer with distributed charge storage elements is proposed in this work. A large memory window is observed due to the formation of nickel-germanium and nickel nanocrystal in gate stack layer. The obviously threshold voltage shift for nonvolatile memory device with the low-temperature oxidized Si/Ge/Ni stack layer which is sufficient for a memory device to define the signal “0” and “1”.Also, the manufacture technology using the low temperature silicon oxide using plasma enhanced chemical vapor deposition system (PECVD). In addition, the nanocrystals were embedded in germanium oxide was also found in this study. However, the behavior for Ni on Ge under thermal treatment was also investigated. The formation of NiGe in Ni/Ge/Si system was found under thermal annealing.