量產型大面積熱電子輔助化學氣相鑽石膜合成裝置之開發

Abstract

鑽石膜在未來有極大的應用價值和發展潛力，許多鑽石膜相關的產品最近也陸續被推出。然而，鑽石膜的應用除了品質、結晶結構及表面型態等基本要求外，最大的瓶頸在於如何降低生產成本。鑽石膜的大面積化成長以及提高成長速率的方法，就是降低生產成本最重要的關鍵技術之一；其次，鑽石膜的平滑化以縮短鑽石膜的研磨加工時間，亦是降低成本的另一種方法。 化學氣相沉積技術包括許多不同方法，其中熱電子輔助化學氣相沉積法由於沉積的加熱面積較能彈性設計，比較容易大面積化，鑽石膜的厚度均勻性亦容易控制，因此非常適合大面積鑽石膜成長。 由於本實驗室執行國科會專利技術移轉，輔導鋒碩科技公司的專利技術商品化工作，學生有幸參與此計劃工作，因此以此量產型設備的設計、改良做為學生的碩士論文題目。此機台的主要特徵在於氣體流場及基材置放座的設計，可有效提升鑽石膜的成長速率以及減少基材在高溫製程中產生的變形量。 研究結果顯示，鑽石膜的成長速率與反應氣體流場有重大的關係，採用強制對流的流場，可將大量反應氣體在熱裂解後強行控制反應氣氛通過基材表面，有效將鑽石膜沉積在基材上以達到促進成長速率的效果。此外，置放座與基材之接觸面積的設計，牽涉到基材熱傳及恆溫的效果，影響基材受熱的均勻性，採用接觸面為實心平面的基材置放座，可有效改善高溫製程的熱變形。 由反應氣體條件控制鑽石膜品質的實驗結果顯示，當氫氣與甲烷的總流量為1700 sccm、甲烷對氫氣的濃度為1.5 %、製程溫度為2100 ℃、反應時間為40 hr時，所成長的鑽石膜之結晶結構以(111)、(220)、(311)的立方晶結構為主，隨著甲烷濃度及反應氣體流量的增加，鑽石膜的成長速率有增加的趨勢，但品質相對逐漸劣化。由SEM觀察結果發現，基材表面的粗化處理有助於提升鑽石膜的成核密度，但不當的粗化處理和粗化程度會影響鑽石膜表面粗度的均勻性。 研究中以兩段式成長方式的設計來解決鑽石膜厚度不均及表面粗度過大的問題，第一階段以較高的甲烷濃度及反應氣體流量來形成微細多晶鑽石膜；而第二階段是以第一階段生之微細多晶的微晶粒為結晶成長晶種，在較低的甲烷濃度及反應氣體流量來獲得高品質微細晶粒且表面平滑的鑽石膜。由n&k及AFM的觀察結果顯示，厚度均勻性為4.85 %，表面粗度平均值為109.35 nm，大大的改善了厚度均勻性及表面粗度。

There is much potential and application on diamond films and many syntheses methods of diamond films had already been presented recently. However, the challenge of the application of the diamond films within the physical quality, and the structure, and the morphology of the diamond films is the manufacturing cost. Increasing the deposition area and the deposition rate of the diamond films is one way of the solution of decreasing the cost. Moreover, smoothing the morphology of the diamond films for shorting the time of the polish process is another way of the solution. There are many different kinds of the CVD system. Comparing with other chemical vapor deposition systems, the hot electron enhance chemical vapor deposition is suitable for large area synthesis because of the superiority of wide deposition area and good uniformity of the thickness. I join this project and participate in modification the commercial HF-CVD machine for carrying out the patent technology of the National Science Council to Fo-So Technology Company. And the subject has been the study of my paper. In this study, the deposition of the machine of Fo-So Technology Company is the largest one of present. The design of the gas flow field and substrate holder would increase the growth rate of the diamond film and decrease the bending size of the substrate by high temperature during the process. According to the result of the experiment, the gas flow field would influence the growth rate of the diamond film. The high temperature of the tungsten wire separate the reaction gas and diamond deposit on the substrate because of the nonnative force gas flow field. Then, the result shows it could increase the growth rate of the diamond film. In addition, the contact area between the substrate and the holder would also influence the temperature of substrate control and the capacity of the heating conduction. Thus, it would vary the deformation of the substrate during process. The structure of the diamond films is the tetrahedral cubic crystalline. The parameters of the experiment are 1700 sccm of gas flow, and 1.5 % of methane concentration, and 2100 ℃ of process temperature, and 40 hr of reaction time. As the concentration of the methane increase and the gas flow rate increase, the growth rate of the diamond film increase, but the quality of the diamond film decrease. Based on SEM, roughing the surface of diamond film would enhance the nucleation density, but decrease the uniformity of the thickness and the roughness of the morphology of the diamond film. The experiment result shows that the growth rate and the thickness uniformity of the diamond film are 0.507 µm/hr and 26.20 %. This sample would not be suitable for the polish process. Finally, using two-step growth way could improve the uniformity of the thickness and the roughness of the morphology. The purpose of the first step is to deposit the smallish poly diamond films. Then, the second step results the high quality of the smooth surface of the diamond films on the smallish poly diamond film of the first step. By this way, it decreased the uniformity of the thickness and the roughness of the morphology of the diamond film. Out experiment results show that the uniformity of thickness and the overage roughness of diamond films are 4.85% and 109.35nm, respectively by using two-step growth method.