應用表面改質實現微晶片自組裝之製程開發與分析

Process Development and Analysis of Self-Assembly Microchips with Surface Modification

張家壽(Chia-Shou Chang)

指導教授 ： 朱錦洲

共同指導教授 ： 汪若蕙 ； 吳恩柏(Enboa Wu)

國立臺灣大學/工學院/應用力學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.00192

摘要

自組裝是一種可以將微小結構自動接合的一種技術，由於電子或光學元件的尺寸微小化，隨之產生尺寸效應，進而衍生出許多問題，包括機器手臂無法順利進行取放機制、序列式的取放太耗費時間成本，因此我們需要一套經濟且有效的構裝方法，而自我組裝技術成為解決的方案之一。本文首次發展一種兩階段式（two-step）的自組裝技術，即暫時性自組裝技術結合共晶銲錫（eutectic solder）加熱融熔，進而達到永久性接合與電性連結的雙重目的。我們藉由表面改質（surface modification）的方法控制晶片與基板表面特性，使其在水中產生親疏水性（hydrophilic-hydrophobic）效應，而熱力學定理的熵增加現象進一步造成晶片與基板之間自發性的裝配過程。當完成第一階段自組裝動作後，我們利用銲錫凸塊與助焊劑產生第二階段的加熱自對位過程，以完成整個兩階段式的自組裝過程。
除了前述所發展兩階段式自組裝技術，本文亦設計一新式的釋放技術，實現了兩接點（two-pads）的自組裝技術，同時利用發展的模擬工具進行解釋與說明，我們發現單接點組裝結果以長方形為佳，組裝方式為平移後再進行旋轉接合；兩接點組裝結果以兩正方形為佳，組裝方式為平移與旋轉同時接合。另外也可藉此設計不同接合大小形狀與排列方式，以獲得最佳的組裝能力。
最後，利用推導出的理論模型與得到的力學實驗值作一比較，以驗證其正確性。另外，我們由楊格方程式配合歐文-文特方法（Owens-Wendt method）計算出水中元件之間的接觸角（contact angle），判斷其接合的好壞，進而得到製程上的最佳參數，此技術與表面黏著（surface mount technology；SMT）與覆晶構裝（Flip Chip）技術相容，可用於發光二極體（light emitting diode；LED）、無線標籤（RFID）、微機電（MEMS）、生醫（biomedical）元件的領域。

關鍵字

自組裝 ； 兩階段式 ； 共晶銲錫 ； 表面改質 ； 親疏水性 ； 兩接點 ； 接觸角

並列摘要

Self-assembly is to transform a system from a disordered state to an ordered state, meaning that microstructures automatically assemble on the substrate. Conventional assembly technology has adopted “pick and place” which picks microchips from a wafer and placing them onto the substrate. But this technique encounters speed and cost constraints when chip size is reduced to the micrometer scale. Hence, an economic and effective self-assembly method is very important. We demonstrated a technique for temporally self-assembling silicon microchips onto a silicon substrate and performing further self-alignment at a high temperature to form permanently electrical connection by the eutectic solder bumps. We used surface modification to control the hydrophobic-hydrophilic surface properties of patterned microstructures and substrates to result in a spontaneous wetting. After the first step spontaneous self-assembly process, the second step self-alignment process is followed by means of solder-based surface tension.
On the other hand, we also designed a new releasing mechanism to realize the two-pads self-assembly technique. Meanwhile, we developed a simulation model to explain the phenomenon. The rectangle-shaped pad represents the better assembly performance than square-shaped pad, and the displacement model occurs earlier than rotation model for the single-pad self-assembly. In addition, the two-square-shaped pads represent the better assembly performance than one-rectangle-one-square-shaped pads and the displacement model coincides with rotation model at the same time for the two-pads self-assembly. Also, use of different bonding sizes and shapes help enhancing the self-assembly performance.
At last, the surface force model is provable because experimental result is close to this model. We also combined Young’s equation with Owens-Wendt method to calculate the contact angle between the microchip and substrate in water. Then, we can distinguish the bonding and obtain the optimization. This technique is compatible with the surface mount technique (SMT) and Flip Chip technique. The presented technique could be applied to assembly of light emitting diodes, RFID tags, MEMS components, micro-integrated circuit devices or other types of microstructures.

並列關鍵字

self-assembly ； two-step ； eutectic solder ； surface modification ； hydrophobic-hydrophilic ； two-pads ； contact angle

參考文獻

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