有機金屬化學氣相沉積(metal organic chemical vapor deposition, MOCVD)為在晶圓上生長氮化鎵、砷化鎵薄膜的方法。這種薄膜成長的技術需要精準地控制氣體流量、壓力以及加熱器的溫度，確保薄膜的生長速率以及晶圓上的溫度符合製程需求且具備足夠的均勻性。為了達到上述條件，我們期望建立一個具可信度的數值模型來計算MOCVD腔體內的熱流場及化學反應並應用到機台或是製程上的設計。本研究中，主要分為兩個模型。模型一涵蓋較完整的腔體內部構造，而此一模型中包含了三個獨立的環狀加熱源和載盤、晶圓以及製程流道等等，主要目的為用來計算腔體內的熱流場，來獲得晶圓上的溫度分布及流道內壓力及速度等結果。模型二為了節省計算資源，僅將模型一的製程流道獨自建立出來，並運用模型一的溫度計算結果作為邊界條件，計算薄膜成長的化學反應，來獲得薄膜的成長速率以及均勻性。
在初步結果與討論中，我們先將模型一所計算出的晶圓溫度與實驗結果相互驗證，並且也對三個加熱器在不同製程溫度下進行最佳化，使晶圓上的溫度分布更加均勻。建立起具可信度的熱流場模型後，再將溫度與壓力輸出，代入化學沉積的模型作為邊界條件。而在薄膜的成長速率及均勻度上，我們藉著對晶圓圓周(θ)方向積分並除以晶圓自轉一圈所經過時間的方式得到整塊晶圓的平均生長速率。
除了溫度場及化學場的探討，我們也將實際機台所遇到之工程問題放入本文討論，對於工程問題進行案例分析，案例一為晶圓上的溫度高低會受到均熱板公差大小的影響，當填充氣體為氫氣時，公差+0.01mm會使晶圓平均溫度約增加0.2℃，填充氣體為氮氣且在同一公差大小下會使晶圓溫度約有1℃的差異。案例二為加大加熱器保護氣體(heater purge, HP)流量對於薄膜生長速率的影響，在HP流量為3L/min時，薄膜在晶圓上的生長速率較均勻，而當HP加大為15L/min時，薄膜邊緣的生長速率下降，造成不均勻度提升，因此我們針對腔體內的幾何做改變，例如在流道後方開孔使流入製程區域之HP減少，藉此改善措施提升薄膜均勻度。

Metal organic chemical vapor deposition (MOCVD) is the key technique used for developing thin film materials, such as GaAs, InP, and ZnO, on semiconductor wafers. The technique requires the gas flow, heat transfer, and temperature uniformity on the wafer surface to be carefully controlled, so as to ensure that the thin film’s growth rate is appropriate and spatially uniform. To help serve such needs, a reliable numerical model that allows us to accurately calculate the fluid dynamics and heat transfer in the chambers clearly is highly desirable for MOCVD equipment and process design. Moreover, thin film growth also is calculated in our computations. But to overcome the computational resource limitations, we break down the computations into two models. In the first model (Model 1), only the flow and thermal fields are calculated. The temperature distributions on the wafer and ISP surfaces then are extracted and used as the thermal boundary conditions in the second model (Model 2), in which the chemical reactions and film growth are calculated in a reduced computational domain. Through appropriate parameter setting, the results of this numerical approach compare favorably with measurements on actual equipment. Moreover, using this approach, we also study two engineering problems encountered on practical equipment. Specifically, in Case 1 the sensitivity of wafer temperature on the dimensional tolerance of the isothermal plate is examined and is found to be 1 ℃/0.05mm in H2 and 3 ℃/0.05mm in N2 respectively. Meanwhile, in Case 2 we examine how the flowrate of the heater purge gas on the film growth rate, and a sweet range of gas flowrate can be identified.

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