Effect of ultrasound agitation on the properties of copper electrodeposition in micro-via

摘要

Micro-via is the most important interconnecting element in three-dimension (3D) packaging, as it provides a vertical interconnection method with the short distance between chips. The micro-vias are firstly etched by BOSCH type deep reactive ion etching (DRIE), and then metallized by electrodeposition. As the micro-vias used in 3D packaging are usually with very small size (several or tens of micron meter in diameter) and with high aspect ratio, the metallization of the micro-vias is very challenging. Defects, such as voids, seams and pitch off, are needed to prevent. This paper proposes an effective method to achieved no defect filling of the micro-via. With ultrasound assistance, the filling rate at the bottom is evidently improved. Due to the faster filling rate near the bottom than that near the opening of the micro-via, void-free fill of the micro-via is achieved. With the help of the ultrasound agitation, the filling ratio of the micro-via is improved from 81.31% to 100%.