High Speed Copper Plating Process for IC Substrate

Abstract

The integrated circuit (IC) substrate occupies an interesting place in electronic devices. They serve as the bridge between the integrated circuits and the PCB. In this connecting point, they must meet the requirements of both worlds. They must provide the high density of connections to match the IC chip, while at the same time be a stable and robust platform for the chip to reside on. The IC substrate feature sizes and uniformity requirements are moving closer to what is required in the semi-conductor industry, except these substrates must be made at a scale, speed, and cost expected in the PCB industry. In this paper, we present an acid copper electrolyte for plating 2 in 1 redistribution layers (RDL), with small vias and fine lines down to 10µm wide. The electrolytic process successfully plates these features, while maintaining a uniform surface across the panel. The 510 mm x 515 mm panel had less than 5% variation in Cu thickness. The electrolyte was evaluated in a vertical continuous plating (VCP) style tool and a tool that plates panels at high speed. The standard VCP tool operated around 1.0 – 3.0 ASD, whereas the high-speed plater operated around 4.5 – 6.5 ASD. The obvious benefit of the high-speed tool was to reduce the plating time, but it also provided new degrees of control that are not available in VCPs. In either tool, the electrolyte performed well and produced uniform deposits that met the physical requirements that IC substrate applications demand.