| 摘要: | 隨著半導體科技的興起發展，越來越多材料逐漸被應用於半導體製程中。石英由於其特殊的壓電、絕緣、可透光等性質，在生醫與微機電元件皆可看到其相關應用。而在這些元件中，為了避免雜質、微粒、殘留液體等因素影響元件的使用與量測，其表面的疏水性、遲滯性與自潔效果為一個值得探討的議題。因此本研究將藉由鉻金屬薄膜做為蝕刻遮罩覆蓋於石英晶圓上，利用濕蝕刻方式於石英晶圓表面蝕刻出奈米針狀結構。並探討奈米結構對石英表面接觸角與潤濕性之影響。
本文以蒸鍍方式沉積奈米厚度之鉻非連續薄膜作為蝕刻遮罩，再以二氟化氫銨溶液為蝕刻液於石英表面進行蝕刻製作針狀結構。藉由掃描式電子顯微鏡觀察在不同蝕刻遮罩與蝕刻時間下，針狀結構外形及其分布情形，並利用文獻中各種模型進行分析。
研究結果顯示，所製作之結構由於薄膜成長不均勻，導致結構分布不均且存在許多缺陷。石英晶圓經由本文製程蝕刻後，其表面由原本之親水性轉變為疏水表面。靜態接觸角量測中，本文發現當結構分布密度較高時，試片接觸角與Cassie-Baxter模型所預測之接觸角相近；然而隨著結構分布密度的減少，試片接觸角將逐漸低於Cassie-Baxter模型之預測值，此乃液滴向結構間滲入所導致。此外，試片結構間因存在較多的缺陷，故在動態接觸角量測中，試片表面之前進角與靜態接觸角值相近；但由於缺陷影響，試片具有較低的後退角，導致試片上液滴遲滯角極大，使液滴在試片上難以滑動或滾動。經由本研究方法所製備之石英晶圓將具有高疏水及嚴重液滴遲滯現象之表面特性。
With the development of semiconductor technology, more materials are used in semiconductor manufacturing processes. Quartz has many special properties, such as piezoelectricity, insulation, and light transmission. It has been widely used in biomedical and MEMS components. In these components, in order to avoid the dust, particles and liquid effects on the operation or performance, the surface hydrophobicity, hysteresis, and self-cleaning properties may play important roles. In this study, we use chromium thin film as an etching mask on the Z-cut quartz wafers. Then, we use the wet etching process to make nanostructures on the quartz surface. Finally, we will discuss how the nanostructures affect surface contact angle and wettability.
In this paper, a nanometer thick non-continuous chromium layer is deposited on the quartz wafer as an etching mask. Ammonium bifluoride solution is used as the etchant to etch quartz to form nanoneedles on the quartz surface. The etched structures for different etching time are observed by scanning electron microscopy and compared with the models from literatures.
In the results, the distribution of structures is not uniform and there are many defects between structures due to the uneven growth of the thin film. The surface wettability switches from hydrophilic to hydrophobic. In the static contact angle measurement, we found that for high structure-density samples, the measured contact angles are close to the values predicted by the Cassie-Baxter model. However, with the reduction in the structure density, the contact angles are lower than that of the Cassie-Baxter model. The reason causes the phenomenon is the droplets penetration into the structures. In addition, the dynamic contact angle measurements show that the advancing contact angles of wafers are close to the static contact angle values, because there are lots of defects on the surface. However, due to the defects, the samples have lower receding angle, and thus the hysteresis on the surface is worse, causing that the droplet is hard to slide or roll on the surface. The quartz wafer prepared by the method of this study will have a high hydrophobicity, but serious surface hysteresis. |
