Study on Electrochemical Deposition of Thick Copper Pillars for Wafer Level Integration

For the miniaturization of microsystems, the trend in semiconductor industries is to enhance package density by using advanced packaging techniques like wafer-level integration and flip-chip bonding. This paper has discussed the optimization of photolithography and electroplating process with AZ10XT and AZ125nXT photoresists to form copper pillars for high-density advanced microsystems packaging. The spin coating cycle, exposure time, and development time are optimized for achieving patterns with better edge resolution. The copper pillars are created by pulse electroplating in acid copper electrolyte with the photoresist molds mentioned above. The fabricated copper pillars are characterized using an optical microscope and confocal Microscope. The copper pillars of 16 µm height with minimum 15 µm diameter and 35 µm height with a minimum 30 µm diameter are achieved using AZ10xT photoresist.