以(CO,CO2,H2)混合氣體成長鑽石薄膜及其電漿光譜分析

Abstract

本研究採用微波電漿化學氣相沉積法, 探討各種不同比例的反應氣體 , 對鑽石成長的影嚮, 並直接由放射光譜儀分析其微波電漿的氣相組成,希 望藉此研究對於爾後低壓鑽石成長基構的建立有更進一步的了解。由50 CO+3 CO 添加氫氣才能成長出鑽石的實驗, 證明 "氫還原" 在低壓鑽石的 成長過程中的確是不可或缺的。此外, 本論文還提出兩個判斷鑽石成長的 重要準則, 其中氫氣流量對鑽石結晶性、長核密度的影嚮與進料氣体的 O/C 比值有關。氣體原源的 O/C 比值越高, 要成長鑽石所需的氫濃度也 要越高。另外, 利用電漿放射光譜也觀查到碳膜的成長和氣相中297nm 與313nm兩特徵峰的產生和消長有密切的關係。要想得到鑽石薄膜的沉 積, 297nm/ 313nm比值要大於1, 且比值越接進1, 越容易得到結晶性良好 的鑽石薄膜。 Microwave Plasma CVD was utilized to study the effect of various ratios of reactant gases on the diamond synthesis. The compositions of gas phase in microwave plasma is analyzed by optical emission spectroscopy. Attempts were made to uderstand more about growth mechanism of diamond synthesis in low pressure environment. It is proven that reducing hydrogen are necessary in low-pressure diamond growth process from the experiment of 50CO+3CO with hydrogenadded to synthesize diamond, the effects of hydrogen flow rate on diamond crystallinity and nucleationdensity are dependent on the O/C retionof reactant gases. If the O/C ratio is larger, the much higher hydrogen concentration were necessary for growth of diamond. Through plasma optical emission spectroscopy, it is observed that the formation and transfer of the 297nm redicals and 313nm redicals were greatly related to the growth of carbon films. There were lots of C redicalsin CO plasma, but additons of hydrogen and CO to CO gas would decrease the C emission. When hydrogen was added, the characteristic peak ratio of 297nm/313nm was more than unity and it is difficult for diposition when CO was added. Besides, the closer to unity the 297nm/313nm was the better quality of diamond film was obtained.