本論文以實驗的方法觀察液體薄膜在旋轉表面上的手指狀不穩定現象與其影響。論文的第一部份主要說明在晶圓旋轉前，靜置於晶圓中心的流體會因為鬆弛時間長短而對旋轉過程中流體薄膜產生的手指狀不穩定現象與薄膜擴展半徑大小產生影響。由實驗結果可知，鬆弛時間長短對於黏度小的液體影響程度比黏度大的流體更為明顯。在固定流體體積與轉盤的旋轉速度情況下，流體的初始半徑會隨著流體黏度變大而減小，因此與初始半徑相關的無因次參數－雷諾數也會因為此因素而變大。在鬆弛階段時，不同黏度流體的擴展速度也會不相同：鬆弛時間小於三分鐘的情況下，高黏度流體的液膜擴展速度遠比低黏度流體的擴展速度小。這種速度變化所產生的擾動效果就是造成低黏度流體在高雷諾數下臨界擴展半徑曲線產生轉折現象的原因，因為在此鬆弛時間內下低黏度流體尚未完全鬆弛。第二部份則證明流體之動態接觸角的變化也會影響薄膜的臨界擴展半徑並提出一個修正的無因次參數－修正邦德數解釋動態接觸角對手指狀不穩定現象所造成的影響。從實驗結果可以知道，在高邦德數與鬆弛時間為零的條件下，臨界接觸角的變化會造成薄膜的臨界擴展半徑與邦德數關係呈現非線性狀態，這是由於邦德數只考慮靜態接觸角的影響；但是在流體的薄膜擴展過程中，接觸角是隨時間變化的函數，因此需要考慮動態接觸角在旋轉塗佈過程中所產生的影響。本論文藉由加入動態接觸角的影響因素修正邦德數，產生一新的無因次參數－修正邦德數，重新歸納臨界半徑與修正邦德數的關係。此時，流體的臨界擴展半徑與修正邦德數變成函數曲線；因此，這一個新的函數關係可以被利用於預測流體的臨界擴展半徑。 This dissertation experimentally investigates the phenomena of fingering instability on a rotating disk. The first part of this dissertation mainly explains that relaxation time affects significantly the radius of a drop relaxing before spin coating especially for liquids of low viscosity. Even for a fixed volume of liquid and rotation speed, the initial film thickness and the corresponding rotational Reynolds number are all changed. The spreading velocities of a liquid front for each viscosity are different in the relaxation stage. For fluids with higher viscosity, the change in the velocity of the liquid front is smaller than that of fluids with lower viscosity within τr < 3 min. It is mainly the effect of a disturbance in the un-relaxed drop of low μ that causes the “turning phenomenon”. Furthermore, the critical radius for the onset of rivulet instability is dramatically altered. In addition, a modified rotational Bond number, which demonstrates the dynamic contact angle of fluid front that affects the dimensionless critical radius, is also proposed in the second part of this work. For high rotational Bond number, the variation of dimensionless critical radius is not linearly proportional to the rotational Reynolds number because of the variation of critical contact angles if the relaxation time is fixed at zero. By modifying the rotational Bond number with the change of critical contact angle, the dimensionless critical radius becomes a function of the modified rotational Bond number.
