雷射熱退火對不同厚度之鍺奈米薄膜形成鍺量子點之影響

Abstract

在我們的研究中，我們使用鍺奈米晶體( Ge nano-crystals )埋在二氧化矽( SiO2 )中作為浮動閘，製作出三層結構的金氧半電容元件。首先，利用電子槍蒸鍍機在二氧化矽上形成一層非晶鍺薄膜，分成3種不同的厚度，接著再使用準分子雷射退火系統( excimer laser annealing system，ELA )打在非晶鍺薄膜上。由拉曼量測發現隨非晶鍺薄膜厚度的減少，其在300 cm -1的單晶鍺訊號與270 cm -1的非晶鍺訊號強度比值變大，推斷較薄之非晶鍺薄膜在雷射退火後，有較好的結晶性。並以聲子侷限效應來做模擬，來得到鍺奈米粒子之尺寸。 由電容-電壓、電導-電壓、電容-時間等電性量測的結果，研究載子於元件中傳輸過程的電荷流失行為，並對照其拉曼分析之結果。再以快速高溫熱退火之方式修復氧化層缺陷，以期達到較好之電荷保持能力。

In our study, we used Ge nanocrystals embedded in SiO2 as the floating gate, create three layers of MOS devices. First, we use e-gun deposition a layer of amorphous Ge thin film, divided into three different thickness, on silicon dioxide. And then useing of excimer laser annealing system ( ELA ) to shot at the amorphous Ge film .From the Raman measurements result ,we find that the signal in 300 cm -1 which is signal of crystal Ge and 270 cm -1 signal which is signal of amorphous Ge intensity ratio become larger, when the amorphous Ge film thickness reduces. Laser annealing with thiner amorphous Ge films,has better crystallinity. And to get the size of Ge nanocrystals by simulation of phonon confinement effect,. From the capacitance - voltage, conductance - voltage, capacitance – time results to known the carrier distribution of the conducting current and then compare with the Raman analysis. We demonstrate that rapid thermal annealing of the oxide layer can repair defects in the oxide and achieve better retention.