本論文著重於發展一套模擬相變化記憶體之分析軟體，我們利用能量守恆定理、電核守恆方程式和結晶理論討探相變化記憶體在結晶相與非晶相的熱、電及結晶特性。

在於結晶過程利用The rate-equation 和 JMAK兩理論來模擬，雖然The rate　equation比JMAK理論具有較精確的計算結果，但是其計算時間過長，計算成本過高。而JMAK理論具有不錯的準確度及計算時間很短，成本很低。在模擬結晶過程中，活化能是一個重要的參數，從文獻中得，在低加熱率過程中，其活化能約為2eV，而在高加熱率過程中，為0.81eV。在研究過程中，發現在高加熱率時JMAK理論具有很高的準確度，所以我們利用JMAK理論來模擬相變化記憶體的結晶過程。

王在以前做過相似的研究，而主要的差別在於王在非晶態過程未加入潛熱，而在結晶態過程只使用溫度判斷是否已完成結晶，其溫度設在170oC。現在我們利用JMAK理論計算結晶分率。在非晶態過程，發現有加入潛熱後，在低操作電壓要求較高的電壓才能相變化，而在結晶過程，發現利用JMAK理論模擬，在高操作電壓過程要求不能太高的電壓，這是因為在高電壓會造成相變化層溫度高於熔點，而造成非晶態的產生。

The focus of the present thesis is to develop the simulation capability to analyze the performance of the Chalcogenide phase change memory devices. The simulations for the thermal behavior, the electrical properties and the crystallization of the Phase-Change Memory in RESET and SET states have been conducted using the energy equation, the charge conservation law, and nucleation theories. The major focus will be on the computations of crystallization using nucleation theories.

Two techniques, the rate equation and JMAK theory, to model the GST crystallization are investigated. The rate equation is deemed to be a more accurate method. However due to the excessive computational effort required, it is not practical to use this technique in real PCM simulation. JMAK model, on the other hand, is less accurate, but if proper parameters are used, the results can be compatible with the rate equations. It was found that the most crucial parameters used in the model is the activation energy, which is function of the heating rate. At lower heating rate, the activation energy is about 2 eV, while at higher heating rate the activation energy is around 0.81 eV. In the real PCM operation, the heating rate is more than 106 0C, therefore the the adopted activation energy should be 0.81 eV. Simulation using the JMAK theory at high heating rate with this activation energy shows good results in comparisons with the measurements available. Therefore, the JMAK model was adopted to simulate the crystallization process in a PCM device.

Previously, Wang [4] has conducted similar simulations of the PCM devices. There are two major differences between the present predictions and Wang’s results. Firstly, in the RESET operation, Wang did not include the enthalpy of fusion heat in the simulation. Secondly, in the SET operation Wang adopted the predefined temperature 170 oC as the criteria to judge the completion of phase change. Instead, the present study employs the JMAK model to determine the fraction of the crystallization. In comparisons to the results of Wang, the minimum voltage required increases slightly with the heat of fusion included in the simulation, which indicates a slightly higher power is required. On the other hand, the voltage required to complete the SET operation using the JMAK model does decrease at higher BEC width comparing with the results from Wang [4].

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