在矽晶蝕刻槽內沉積鑽石膜之研究

Abstract

本實驗採田口氏實驗規畫法分析製程參數對沉積鑽石膜於矽晶蝕刻槽內之影響。鑽石膜是以微波電漿化學氣相沉積法採氫氣與甲烷為反應氣體而製成。矽晶蝕刻槽的製備是採用微影蝕刻製程以SiO2為冪罩(Mask)及KOH與異丙醇為蝕刻液而完成。分別以SEM和Raman光譜技術觀察表面形貌及評估鑽石品質。以Raman光譜偏移法估計薄膜殘留應力。以及用XRD來決定結晶的優選取向。由實驗結果。可得下列結論： (A)在比較平面矽晶上與具備蝕刻槽之矽晶平面上沉積鑽石膜的行為，可以發現：(1)除了殘留應力外，兩者在沉積速率與鑽石品質的主要貢獻率的參數方面，幾乎是一致的。(2)影響殘留應力的主要參數分別為沉積時間（貢獻率約53%）及微波功率（貢獻率32%）。(3)在表面形貌上可看出在具備蝕刻槽之矽晶平面上沉積的鑽石膜比在同一沉積條件下沉積於無蝕刻槽之矽晶平面上的鑽石膜晶形完整且有較高的品質。(4)在平面矽晶上影響XRD I(111)/I (400)主要的參數分別為氣氛壓力與甲烷濃度的交互作用(66%)、甲烷濃度(21%)及氣氛壓力(12%)。換言之，由XRD I (111)/I (400)的比值大小依序排出沉積條件為：（甲烷濃度低）＋（氣氛壓力低）＞（甲烷濃度高）＋（氣氛壓力高）＞其他的組合。 (B)在比較於平面矽晶上與矽晶蝕刻槽內沉積鑽石厝的行為，可以發現主要貢獻參數分別為：(1)在沉積速率方面是甲烷濃度(41% ，52%)氣氛壓力(29%, 24%)及微波功率（或沉積溫度）(26%, 21%)。(2)在鑽石品質方面為微波功率(69%, 52%)及甲烷濃度(17%, 38%)。(3)較高的甲烷濃度與較低的微波功率會使得沉積速率加快。(4)在鑽石品質較高的沉積條件下，沉積速率較低。兩者呈現相反的態勢。(5)較高的鑽石品質會使得薄膜中的壓應力變小。

Effects of processing parameters on diamond deposition in the etched trenches of Si wafer were studied by the Takuchi method (an orthogonal experimental analysis method). Diamond films were deposited by a microwave plasma chemical vapor deposition (MRCVD) system with CH4 and H2 as the source gases. The trenches of the Si wafer were obtained by a photolithography process plus a wet etching process with SiO2 as the mask and KOH+Isopropanol as the etchant. Morphologies and diamond quality (or diamond content) of the films were characterized by SEM and Raman spectroscopy, respectively. The residual stresses of the films were evaluated by Raman shift method. The preferrd orientations of the films were determined by XRD. The experimental results show the following conclusions.: (A) By comparing the deposition behaviors on the flat surface of Si wafers with and without the etched trenches at the sides, the results show: (1) Except the residual stress, the main parameters with the greater contributions to the film deposition rate and the diamond quality are almost the same. (2) The main parameter for the residual stress is deposition time (about 53% contribution) and microwave power (32% contribution), respectively. (3) In terms of film morhologies at the same deposition conditions, the films for the former case show more faceted crystals and better diamond quality. (4) For the flat surface, the contributions of the main parameter to I(111)/I(400) of the films are interaction between system pressure and CH4/H2 ratio(66%), CH4/H2 ratio (21%) and system pressure (12%). In other words, the favor conditions for a greater I(111)/I(400) value are in the order of : (CH4/H2 ratio=low) + (system pressure=low) > (CH4/H2 ratio=high) + (sytem pressure=high) > other cases. (B) By comparing the deposition behaviors on the flat surface and in the trenches of Si wafer, the results show that the contributions of the main parameters: (1) to the deposition rate are CH4/H2 ratio (41%, 52%), system pressure (29%, 24%) and microwave power (or deposition temperature) (26%, 21%), respectively. (2) to diamond content in the films are microwave power (69%, 52%) and CH4/H2 ratio (17%, 38%), respectively. (3) The favor conditions for a greater deposition rate are a higher CH4/H2 ratio and pressure, and a lower microwave power. (4) The favor conditions for a higher diamond quality are opposite of the favor condition for a greater deposition rate. (5) A greater diamond content in the films will give rise to a smaller compressive stress.