以微波電漿化學氣相沈積法在二矽化鈷基材上成長鑽石薄膜之研究

Abstract

鑽石具有許多優異的材料性質，可以廣泛應用於電子、光電、光學與機械等領域，尤其是在電子、光電與光學領域的應用，需要高品質具方向性（oriented）或磊晶（epitaxial）的鑽石膜。但是，鑽石成核與成長機制仍有許多疑點待釐清，使得鑽石膜的量產製造及應用受到相當的限制。 本實驗中利用微波電漿化學氣相沈積法（MWCVD）及偏壓輔助成核法（BEN），藉由不同的加偏壓方式、改變CH4氣體濃度、壓力及微波輸入功率等條件，在CoSi2基材上成長鑽石膜，並在Si基材上作部分對照實驗，藉以比較。藉由XRD、SEM、EDS與XTEM的分析，希望能對鑽石膜在CoSi2基材上的成核與成長特性有所瞭解。 實驗結果顯示，在CoSi2基材上以負偏壓沈積鑽石，最密成核密度約大於1.5 x 107 cm-2左右，跟在Si基材之結果類似，都可以得到（100）面方向的鑽石，但是在CoSi2基材的上成核密度比Si基材低。在CoSi2基材上以正偏壓沈積鑽石，不易生成（100）面方向鑽石晶粒，但成核密度可以提高至約為大於6.4 x 109 cm-2左右。改變CH4氣體濃度及微波輸入功率會對鑽石膜的密度與形貌有影響。另外，電漿與電場的特性對於鑽石成核與成長階段的影響，也不容忽視。

Diamond has many excellent material properties. It has the great potential to be extensively used in electronics, photo-electronics, optics and mechanical applications. The applications in electronics, photo-electronics and optics areas demand high-quality oriented or epitaxial diamond films. Although it has been shown that the epitaxial films can be deposited, there are still unknowns about the mechanisms of nucleation and growth for diamond. It makes the mass-production and applications of diamond films to be limited. In our experiments, we use the microwave plasma enhanced chemical vapor deposition method (MPCVD) and the bias-enhanced nucleation method (BEN) to grow diamond on CoSi2 substrates, by using different bias conditions such as different kind of electrodes, changing CH4 volume concentration, pressure and microwave input power etc. Diamond grown on Si substrates has been carried out for comparison. As a result, we find that we can grow (100) diamond crystals by using negative bias on both CoSi2 and Si substrates, the nucleation density of diamond is higher than 1.5 x 107 cm-2 on CoSi2 substrates which is lower than on Si substrates. However, the nucleation density of diamond higher than 6.4 x 109 cm-2 can be obtained by using positive bias on CoSi2 substrates. Whereas the (100) orientation of diamond crystals is lost. The nucleation density and morphology of diamond crystals are affected by changing CH4 volume concentration and microwave input power. Besides, the properties of plasma and electric field have effects on the nucleation and the growth stages of diamond, and should not be ignored.