利用常壓噴流式電漿改質聚醯亞胺表面並應用於無電鍍銅之製程

Abstract

聚醯亞胺因其高熱穩定度與高彎曲性被廣泛應用在半導體製程，而銅因其低成本與高導電性是為工廠製程中常用金屬。在實際製程上，金屬與高分子表面的貼附好壞甚為關鍵，因此，如何提高其表面能進行反應極為重要。 此論文中，我們使用介電質放電形式的噴流式大氣電漿，利用介電質放電的低功率、低溫、均勻的特性；噴流式電漿的氣體帶動流場不直接造成樣品毀損，且代測樣品較不受限；大氣電漿在常壓下不須高成本的真空設備；電漿本身的高反應性；我們嘗試在一般的無電鍍銅製程前，加上電漿前處理，利用高反應性的離子等轟擊表面，造成表面改質使後續的無電鍍製程更有效率的進行。 研究中，利用一分鐘的電漿前處理，即可在兩分鐘的無電鍍銅程序中，均勻且穩定的生成銅在聚醯亞胺表面，且達到ISO1的貼附標準。除了使用一般工廠製程中常見的Kapton聚醯亞胺以外，也嘗試將製程推展到具有不同官能基的聚醯亞胺，可得到相似的效果。同時，我們利用電腦時間解析照片的紅綠藍三色彩元素隨時間在各個區域的變化，將聚醯亞胺以表面遮罩覆蓋後，放入電漿測試，證明有經過電漿處理的區域可以明顯提升無電鍍的起始速率，且用於無電鍍的終點判斷，讓我們在表面圖案化的製程中，克服單一片聚醯亞胺本身的差異，選擇適當的反應終點，以達成較好的圖案化樣品解析度，我們嘗試不同線寬的長方形比較轉印忠誠度，得到最小的穩定解析度在邊長為1.25 ± 0.04 毫米的正三角形大小。未來，藉由步徑馬達的使用，可望將此反應延伸至工廠的軸對軸(Roll-to-Roll)製程中，用以減少反應時間與得到更好的吸附效果與均勻度。

Polyimide (PI) is of great interest due to its flexibility, high thermal stability, low cost and high conductivity of copper. However, PI with low surface energy causing the better adhesion to be more critical in copper coating processes. The atmospheric pressure plasma jet (APPJ) used in this work is a dielectric-barrier-discharge (DBD)-type plasma jet, a home-made system that can be operated under atmospheric pressure powered by a commercially available high voltage power source. We use DBD for its low energy consumption, low temperature and umiform characteristic; APPJ for its remote fluid field without damaging the surface and the flexibility for sample type. After the plasma treatment, silver nitrite ink, serving as the activated agent, is coated on the PI surface. Electroless copper plating is then performed by soaking the PI in the copper plating bath and finally quantified by cross-cut test and Red Green Blue (RGB) time-resolved analysis. The results showed that the adhesion of the copper film can be greatly improved to ISO1 by the one minute plasma pre-treatment and followed by two minutes copper plating process. Also, this process can not only used for Kapton PI, but also for PI of different functional groups. Moreover, the RGB time-resolved analysis showed that the initiation time for copper plating can be reduced up to fifty percent by this system. Furthermore, we can use the RGB analysis to point out the indication for end-point detecting in the electroless plating process. This can be used for the patterning plating process for the high selectivity for copper. We tried to test the pattern fidality by different width of lines. With the treatment, we can steadily form the minimum line with 1.25 ± 0.04 mm width. This work presents the use of an atmospheric pressure plasma jet (APPJ) for improving the adhesion and decreasing process time. Further research of step-motor use could shed light on the roll-to-roll industrial application in the near future.