Piranha Clean 製程技術於金-金熱壓式鍵結接面清潔度之研究及其應用於低溫熱壓鍵結技術之探討

Abstract

本論文利用Piranha 潔淨技術清潔金表面有機氧化物等污染，並可降低金表面的接觸角，提升表面自由能，將此技術應用於金-金熱壓式鍵結接面以達到低溫可熱壓鍵結技術之探討。經由實驗驗證於Piranha 潔淨技術，可將原本傳統熱壓式接合所需溫度300度，經由本潔淨技術在壓力為100MPa，接合時間180秒之接合條件下將結合溫度降低為160度，此技術將可應用在需要低溫接合之晶片封裝而不須花費高額的費用。

Typical solder bonding process for flip chip assembly is performed above 200°C. The bond usually comes with thermal stress, misalignment, structural damage resulting in the reliability problem of packaging assembly. Besides, the pitch size of electrical input/output (I/O) is usually limited by the size of solder ball that further restricts the flip chip bonding technique for high density interconnecting application. Therefore, it is critical to develop the chip assembly technique with low processing temperature and small bump size. In this paper, piranha cleaning process combined with a conventional under bump metallization (UBM) process have been developed for realizing low temperature Au-Au thermally compressive bond (<200牵C) and it has shown the potential for the applications of fine-pitch interconnect and System-on-a-Packaging (SOP). Experimental results show that the gold content in the bonding surface can be increase 33.7% after a 240 seconds piranha cleaning to realize a Au-Au thermally compressive bond with a contact resistance of 45mΩat the conditions of 160℃ and 100MPa applied pressure.