於微波電漿氣相沈積系統中使用偏壓法於銅基材上成長鑽石之研究

Abstract

近年來發現在使用化學氣相沈積法沈積鑽石的過程中，於成核階段加上偏壓前處理時，其具有明顯促進鑽石晶粒成核及方向性的效果，此結果說明偏壓前處理之方法或許可以促進鑽石之異質磊晶，進而使得鑽石能夠應用於電子元件上。 在本研究中主要探討於微波電漿化學氣相沈積系統中，偏壓前處理對於鑽石於銅基材上之成核及成長特性，使用銅作為基材的原因在於鑽石與銅皆為立方晶體結構，且具有相似的晶格常數，故認為其可作為成長磊晶鑽石的良好基材。實驗中使用-150V到-350V等不同的偏壓大小，以及從2%到25%等不同的甲烷濃度，以探討偏壓條件對於鑽石成核密度、結晶方向性及晶體品質的影響，並希望能得到關於鑽石於加偏壓下之成核機制訊息。 實驗結果顯示偏壓前處理對於鑽石成核於銅基材的效果雖不如成核於矽基材上明顯，但是也會有促進成核密度的效果，且成核密度也會受偏壓參數如偏壓大小、甲烷濃度不同所影響。其所觀察到的最大的成核密度約為1×107cm-2。由掃瞄式電子顯微鏡及X光繞射儀之分析結果指出沈積於銅基材上的鑽石為多晶結構，但許多鑽石晶粒上會呈現三角形的{111}平面。而由拉曼光譜的分析指出會有石墨相的生成，且濃度越高越明顯。

The application of a biasing pretreatment in microwave plasma chemical vapor deposition(MPCVD) has recently been shown to be an effective method for improving the nucleation density and diamond orientation. The result suggests that biasing pretreatment is a promising method for the application of diamond film as electronic devices. Both of copper and diamond are of cubic structure and similar lattice constant, making copper an excellent candidate substrate for the heteroepitaxial growth of diamond. In this experiment, diamond was deposited on copper by using MPCVD with a biasing pretreatment. The bias voltage and methane concentration was varied in the range from -150V to -350V and 2% to 25%. The dependence of the nucleation density, the orientation of the nuclei, and the crystal quality on the biasing pretreatment parameters was studied. In addition, we hope that we can understand the mechanism of generation of diamond nuclei on copper by biasing pretreatment. The results indicate the biasing pretreatment on copper substrate has less influence on the increase of nucleation density than on the Si substrate. It is found that the density of diamond was also dependent on the biasing pretreatment parameters, such as the negative bias voltage and methane concentration. The maximum nucleation density of the diamond on the copper was approximately 1×107cm-2. The scanning electron microscopy and X-ray diffraction analysis reveals the diamond crystals obtained on copper surface are polycrystalline but most of diamond particles have polygonal shape with {111} facets. The Raman spectrum analysis reveals the presence of graphite.