Electrodepostion Of Micro-bumps Applied To 3-d Electronic Package And Research On Low Temperature Solid State Interconnection Technology

The electronic industry has an increasing demand for micro-system with higher functional density and performance. This demand can be usually met by reducing the feature size and adopting advanced packaging and integration technology. However, both IC functional density and advanced packaging/integration technologies have reached to their limits in 2-D in recent years. 3-D packaging/integration technologies are hoped to solve the problem and to make Moore's Law continue. This technology has advantages of reducing cost, integrating different heterogeneous technologies, reducing interconnect time delays and power dissipation. 3-D packaging/integration technologies can be divided into three groups, that is 3-D System-on-Chip(SOC), 3-D packages stacking and 3-D stacking with through silicon vias (TSV). Among them, 3-D stacking with TSV is easier to realize than SOC and smaller in volume than packages stacking. Bonding technology is one of the key process technologies among those enabling 3-D stacking with TSV interconnects. The main bonding technologies include adhesive bonding, metal/solder micro-bumps bonding, direct oxide bonding, anodic bonding and glass frit bonding. Among them, micro-bumps bonding technology are paid great attention on because of the bonding lines formed by it are good conductor of heat with excellent mechanical and electronic performance also. The realization of micro-bumps bonding was based on the fabrication of high density micro-bumps. In this article, manufacturing process of Cu micro-bumps using electrodepositing method was researched. The structure of Cu bump/barrier layer/soft metal layer was prepared and was applied to a novel 3-D low temperature solid state interconnection method based on Ni nano cone array (NCA) then.Wetting behavior of electrolyte in the fabrication process was researched in details by contact angle test, SEM observation and surface tension measurement. It was shown that some factors can promote electrolyte soaking photo-etching micro-holes fully. These factors can increase the number of gas nucleus and help bubbles generating and growing near interface between electrolyte and related materials. Preparation process of Cu micro-bumps was made based on these. Influences of current density and electrodepositing time on grain orientation, surface appearance and surface roughness of Cu micro-bumps were research by XRD, AFM and SEM. The feasibility of the mentioned novel interconnection method was proved by SEM observation of cross-sectional bonding samples and shear test on bonding samples. But the optimality condition of interconnecting needs to be further researched.