二階段成長法鑽石場發射陣列之製作及其特性研究

Abstract

鑽石薄膜由於其優異的性質□其應用在用半導體元件及光學元件上是深具 潛力。 本實驗利用化學氣相沉積法(Chemical Vapor Deposition, CVD) 先將Si基板置於鑽石懸浮液中用超音波處盪前處理以提高成核密度, 再以 甲烷氫氣及甲烷-二氧化碳為原料氣體源, 採二階段濃度差成長法, 成長 鑽石場發射陣列。 鑽石陣列是利用鑽石的選擇成長方法以圖樣化後 的二氧化矽當作遮蔽物(mask)將單顆圓形多晶鑽石成長空格中。二階段濃 度差成長法中, 第一階段中我們使用高甲烷濃度以成長出一層類鑽石組織 膜, 第二階段則降低甲烷濃度以成長結晶性鑽石條件來成長鑽石場發射陣 列。 經二階段成長法可得到表面具有微小角錐形狀的單顆圓形多結 晶鑽石場發射陣列, 且具有較多的(111)面、較銳利的刻面、較大的發射 面積、以及在底層的類鑽石組織。使用此作法較使用一般直接成長法更符 合高放射效率的特性。而我們也發覺, 當表面具越小及越尖銳的角錐時有 較高放射效率因其具較小的發射半徑, 或鑽石品質越差時, 放射電流也較 大。 為了更有效的提高場發射電流, 我們嘗試以硼酸三甲酯(B( OCH3)3)為摻雜源(doped source)來製作具摻硼鑽石場發射陣列, 結果發 現經摻硼的鑽石陣列發射電流比未摻雜的高約10 倍。 Synthetic diamond thin films have potential for fabricating high-temperature semiconducting and optical device because diamond has many extraordinary properties. In this thesis, we present two-step deposition processes for producing field emitter arrays (FEAs) coated with diamond, using microwave plasma chemical deposition method (MPCVD). In this experiment, selective growing diamond on Si substrate was performed by conventional lithography using SiO2 as a mask. We use two-step processes to obtain the FEAs diamond film. In the first□step, a pre-coated of amorphous and carbon were formed under a high CH4/H2concentration; in the second□step, after the formation of a pre□coated layer, the CH4 /H2 concentration was lowered, then the FEAs diamond films is obtained. The finer cone-shaped crystalline diamond FEAs can be obtained using two- step deposition method□which possess the much (111) faces□ ultrasharp polycrystalline on the surface of diamond, larger emitting area, and the pre□coated amorphous or DLC layer. Using this processes accord with more emission efficiency than using one-step deposition method. And we found that the poorer the film is, the higher the current.□The smaller ultrasharp protrusion is obtained, the higher emission efficiency.□ In order to increase the emission current of the field emitter. The boron□doped FEAs diamond films is achieved by means of trimethyl borate (B(OCH3)3) vapor was introduced into the CH4□ H2 gas mixture as dopant source. Finally, we found that the emission current of boron□doped diamond is about 10 times than that of undoped diamond film.□