| 摘要: | 有機金屬化學氣相沉積法(Metal organic chemical vapor deposition, MOCVD)是其中一種生長半導體薄膜的方法，其為發光二極體(LED)製程中重要的關鍵技術。在其製程中，膜厚的均勻性及生長速率攸關LED的效率與品質。本研究採用COMSOL Multiphasics商用軟體針對Veeco TurboDisc E400LDM垂直式腔體進行二維軸對稱及三維模擬，探討三甲基鎵(TMG)及氨氣(NH3)反應生成氮化鎵(GaN)的過程中，氣相化學反應式、製程參數及進氣入口設計對薄膜生長速率及膜厚均勻性的影響。
本研究為了簡化模擬的複雜度及以找尋主要主導薄膜生長的化學反應式，首先，先進行氣相反應式的簡化，藉由阿瑞尼斯式方程式(Arrhenius equation)歸類出5條影響薄膜生長速率的反應式。
接著，探討製程參數，如氣體流量(50-200 slm)、載盤轉速(500-1500 rpm)、腔體壓力(10-70 Torr)以及生長溫度(900-1100℃)，對薄膜生長速率及均勻性的影響。模擬結果顯示改變載盤加熱溫度的影響並不明顯；而增加氣體流量可提高薄膜生長速率，但會使均勻性變差；提高載盤轉速及腔體壓力可使邊界層變薄、加快物種擴散，使氣體分布均勻進而得到較好生長速率及膜厚均勻性，但是高轉速及高壓力下，容易在側壁及入口處形成渦旋而導致流場不穩定。
最後，針對進氣入口做優化設計，結果顯示增加入口slot jets數量，可明顯使腔體流場變穩定。同時探討了物種排列方式，對稱排列式設計(入口1)容易使氣體擴散不易，降低薄膜生長速率，而間距排列式設計(入口2)可改善此問題。;Metal organic chemical vapor deposition (MOCVD), one of the important techniques in the manufacturing process of light emitting diode (LED), is a method of growing film on semiconductor. The uniformity of the film is relevant to efficiency and quality of LED. The study investigates GaN growth from trimethyl-gallium and ammonia. It also simulates the 2D axisymmetric and 3D Veeco E400LDM vertical rotation reactor by using commercial computational software, COMSOL. Simulations were performed to study the effect of key design parameters of GaN film growth rate and uniformity, such as chemical reactions, process parameters and design of gas inlet.
In order to simplify the simulation and to find the main chemical reactions leading to film growth, the study was first conducted to explore the gas-phase reactions mechanism.
After that, the study investigated the effect of tuning these manufacturing parameters, such as gas flow rate (50-200 slm), wafer carrier rotation rate (500-1500 rpm), chamber pressure (10-70 Torr), and growth temperature (900-1100℃), on the growth rate and film thickness uniformity. The results showed no significant effects of heating temperature on the growth rate and uniformity. The increase of gas flow rate improves the growth rate of the film but makes deterioration of uniformity. Moreover, enhancing the wafer carrier rotation rate and chamber pressure can allow the boundary layer thinning and accelerate the diffusion of specie, to get a better growth rate and film thickness uniformity. However, the higher speed and higher pressure easily induced the vortex in the side wall and the entrance. It cause instability in the flow field.
Finally, the study of optimization of the gas inlets was done. The results show that increasing the number of slot jets, the fluid flow can be significantly stabilized. The arrangement of species was also been studied. The symmetric arrangement design doesn’t enhance any diffusion of gas. It reduced the growth rate of the film. However, the staggered design can solve this problem. |
