Microcontacts with sub-30 μm pitch for 3D chip-on-chip integration

A low-cost soldering process—based on solid–liquid-inter-diffusion (SOLID)—for low-stress 3D-interconnects will be presented. The simple Cu(Ag)Sn metallurgy enables corrosion resistant contacts with a high melting point and excellent reliability performance. The paper, focussing on material aspects, will comprise a detailed presentation of the process flow, electrical characteristics, reliability assessment and a comparison with standard 3D interconnect approaches. The present available results confirm production readiness of the technology.