為減少半導體旋塗製程中光阻液的使用量，以及增進對旋塗過程中液膜擴展物理機制的了解，本論文採用流場可視化的實驗方法分析液膜擴展過程，並與數值模擬結果作一比較。本論文首先說明旋塗的早期階段，光阻液膜擴展主要與光阻液的注液有關，而液膜波前會因為離心力的作用而產生手指狀不穩定流，伴隨著手指狀不穩定流長度的增加，其寬度同時會受到科氏力的作用而逐漸變寬。在塗佈的早期階段短時間內，所測得的液膜波前位置，與數值模擬分析所得的結果相較，兩者相當吻合。但是隨著時間的增加，由於手指狀不穩定流的生成，所得到的數據，會逐漸與數值模擬分析所得到的結果產生差異。由實驗結果發現：在固定旋塗轉速，光阻液塗滿晶圓表面的狀況下，提高注液流率確實可以減少光阻液的使用量，而實驗與數值模擬發生差異是導因於手指狀不穩定流的產生，因此手指狀不穩定流在旋塗過程當中扮演著非常重要的角色！因此，本論文另外採用矽油做為實驗流體，就噴塗與擴展液滴兩種注液方式，探討手指狀不穩定流在旋塗過程當中的物理機制。從實驗結果發現：無論是以噴塗或擴展液滴方式注液，在低轉速時之手指狀不穩定流之流場型態應為內部區的流動，其力學關係為粘滯力與毛細力之間的競爭，而在高轉速時手指狀不穩定流之流場型態應為外部區的流動，其力學關係為粘滯力與離心力之間的競爭，故在不同轉速時產生手指狀不穩定流的臨界半徑、手指狀數目等變數，要視其所主宰的流場型態來決定。而液膜波前之流動形狀也會由於分子濕潤與離心力的大小而呈現楔形與圓鼻型之差異。另外就噴塗注液方式而言，其產生手指狀不穩定流的臨界半徑、手指狀數目及最大塗佈半徑等數據均較擴展液滴注液方式來得小且少。隨著注液流率的增加其產生手指狀不穩定流的時間將會延後,所以臨界半徑也會跟著增大,而當注液流率不斷的增加,臨界半徑及時間終將會趨於定值而與注液流率無關。 最後，期望能將本論文所提出的光阻減量方法，以及手指狀不穩定流在旋塗過程當中的物理機制，提供給半導體業界，作為改進實際旋塗加工製程之參考。 To reduce the photoresist usage and understand the film spreading process, this study performs flow visualization experiments and numerical simulations. This thesis is the first work to show that in the early stage of the spin coating process, the spreading of photoresist is mainly governed by the photoresist injection. Then, instability fingers are formed due to the centrifugal force. Accompanied by the growth of fingers in length, the Coriolis force broadens the width of fingers. The numerical results agree with the measured liquid front history at a very short time. Difference between the numerical results and experimental data gradually aroused due to the formation of instability fingers. The critical injection rate for fully coating a wafer increases with decreasing injection volume. Under a fixed wafer rotating speed, increasing the injection rate can significantly reduce the photoresist usage. Since the fingering instability plays a very import role during spin coating, a study of fingering instability for both the injected liquid and a released drop of silicon oil is presented. However, the injected liquid or released drop, the flow field is inner region flow in the low rotational speed and the flow field is outer flow region in the high rotational speed. Due to the effects of molecular wetting and centrifugal force, the shaped of liquid is “wedge” or “nose”. Compared to the results for a released drop, the effect of the liquid injection tends to decrease the critical radius, number of fingers, and maximum fully coated radius. The results will provide the design and operation of spin coating process.
