High-Density Room-Temperature 3D Chip-Stacking Using Mechanical Caulking With Compliant Bump and Through-Hole-Electrode

In this study, we employ a novel compliant bump in 3D chip-stacking using mechanical caulking. The compliant bump prepared in this work has a cone-like structure and is made of Au. It is fabricated using an “undercut resist method,” which combines undercut resist pattern formation with electroplating. The size of the compliant bump (approximately 10–30 μm in diameter) is much smaller than that of the stud bump. We demonstrate that by using a mechanical caulking process with a compliant bump and a through-hole-electrode, high-density through-hole-electrode interconnection (I/O number: 8,000, pitch: 20 μm) becomes possible, even at room temperature.