Effect of Ultrasound on Copper Filling of High Aspect Ratio Through-Silicon Via (TSV)

Since voids and seams are usually formed during the process of filling TSVs with high aspect ratio, good methods that can achieve the superfilling of TSVs are eagerly needed. This paper presents a new copper electroplating method with the assistance of ultrasound. Result shows that ultrasound cannot only improve the TSV filling quality but also can quicken the filling rate. Ultrasounds with different powers are applied to explore the most optimized condition for TSV filling. When ultrasonic power is set as 105 W, TSVs with the diameters of 20 μm and depths of 200 μm are all fully filled in 5 hours. Additionally, acoustic streaming and cavitation effect conducted by ultrasound during the TSV filling process are also analyzed, which contributes to increasing the mass transport process and reducing the concentration polarization of electrodes.