利用準分子雷射退火製作含有鍺奈米晶體之金氧半電容

Study of Germanium nanocrystals in the MOS device with excimer laser annealing

陳晶盈(Jing-Ying Chen)

指導教授 ： 管傑雄

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.10575

摘要

在我們的研究中，我們使用鍺奈米晶體(Ge nano-crystals)在二氧化矽(SiO2)中作為浮動閘，製作出三層結構的金氧半電容元件。首先，鍺奈米晶體是利用電子槍蒸鍍機在二氧化矽上形成一層非晶鍺薄膜後，利用準分子雷射退火系統(excimer laser annealing system，ELA)去製作鍺奈米晶體。由SEM和AFM圖，我們可觀察到鍺奈米晶體，其尺寸隨著雷射處理的功率不同而有差異。我們使用羅倫茲擬合(Lorentz fitting)對拉曼頻譜量測結果作分析，試圖將結晶鍺(c-Ge)和非晶系鍺(a-Ge)的訊號分開討論，並研究訊號強度和雷射功率的關係。
由電容電壓、電導電壓、電流電壓等電性量測結果，研究載子於元件中傳輸過程的電荷流失行為。對於載子交換的機制，我們建立了一個陷阱模型來證實電荷保存的特性與載子交換時間常數τ的關係。我們的模型是建立在SRH的理論上，我們首先量測電容與電導對電壓的關係，再把陷阱電容 (Trap capacitance) 跟電導 (Trap conductance) 求出，進而求出載子交換的時間常數，並探討載子交換時間τ和施加偏壓、雷射功率大小、陷阱密度等的關係。

關鍵字

準分子雷射 ； 鍺奈米晶體拉曼 ； 遲滯曲線 ； 陷阱電容 ； 陷阱電導

並列摘要

In this work, we use germanium nano-crystals (Ge NCs) as a floating gate in silicon dioxide (SiO2) matrix, and then fabricate a MOS capacitor with a tri-layer structure. At First, we use E-gun system to evaporate an ultra-thin Ge layer on SiO2. Then, we use excimer laser annealing system to fabricate Ge NCs. From SEM and AFM images, we ensure that Ge NCs are formed. The size of nano-crystals is dependent on laser power density. We use Lorentz fitting to analyze the Raman spectrum .We use this method to separate the signal of amorphous Ge from that of crystal Ge and investigate the relation between Raman signal intensity and laser power density.
From the capacitance-voltage (C-V), conductance-voltage (G-V), current-voltage (I-V) results, we can investigate the carriers transmission process and charges loss mechanism. For the carriers exchange mechanism, we also propose a single trap model to describe the relation between charge storage characteristics and carrier characteristic time constant. The model is based on SRH theory. C-V, G-V measurement results are used to get trap capacitance, trap conductance and characteristic time constant τ. We utilize our trap model to analyze the relation of biasing voltage, laser power density and traps density.

並列關鍵字

excimer laser ； Ge NCs ； Raman ； hysteresis curve ； trap capacitance ； trap conductance

參考文獻

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