Pioneering the Leading-Edge Adhesion Enhancement System for the Future of Package Substrates Bonding

In microelectronic assembly, the formation of a robust and reliable bond between copper conductor tracks and dielectrics is a must. This necessity becomes even more pronounced in the area of high-density interconnects, where the demand is greater than ever for fine line and space circuitry. The traditional surface roughening processes, that have been relied upon to improve the adhesion of dielectric materials to copper have become impractical. The excessive etching of the conductor tracks has a detrimental effect on their characteristics and signal integrity. With the current challenges in the packaging substrate industry, a novel approach to adhesion improvement is essential. The new process must be independent of surface roughening or etching, have excellent lamination material compatibility and be cost-effective. In this report, a new type of organo-silane adhesion promoter is designed to chemically react with Cu and dielectric materials. It is successfully synthesized in-house with a focus on route optimization, reproducibility, and scale-up. The new promoter improves the initial adhesion strength of ultra-smooth Cu to insulating build up films and prevent loss of adhesion when the substrates are exposed to extremely high temperatures and or/ humid external environments. In addition, the promoter significantly reduces wedge void defects on blind micro vias (BMV) by strengthening the Cu-dielectric interface of patterned substrates against aggressive desmear conditions. High corrosion resistance demonstrated by electrochemical tests. A comparison with a low etch adhesion promoter (LEAP) system will show that the roughness is no longer necessary to ensure a reliable bonding. The newly developed non-roughened solution enables state-of-the-art IC substrate packaging. It also meets the technical specifications of major microprocessor manufacturers.