3D TSV Plating and Bumping: Rising to the Challenge

July 22,2015

3D integration using through silicon vias (TSVs) promises a fundamental shift for current multi-chip integration and packaging approaches, but it brings more difficulties in Cu electroplating.

After many years and R&D effort, the challenges of Cu-filling 3D TSVs have been overcome and processes are ready for manufacturing. Nonetheless, it’s still one of the more costly steps in 2.5D interposer and 3D-IC manufacturing, so now the big push is to optimize the process to reduce cost of ownership (CoO).

Reducing plating time is one way to do this. However, this process optimization has unearthed its own set of challenges. Increasing plating speed will cause "pinch-off" voiding. Achieving fast bottom-up filling is less about the equipment, and more about the plating chemistries. Cu plating additives need to polarize field areas, while also depolarizing the inside of the TSV. At Dow, we’ve synthesized Cu plating additives to optimize the polarization/depolarization balance, which helps to improve the uniformity and filling capability.

In addition to the challenges faced with Cu TSV plating, challenges with soldering TSVs or redistribution layers running from TSVs to Cu pillars and micro bumps have been tackled. Remember RoHS, the Restriction of Hazardous Substances Directive? It’s been an ongoing topic of discussion since it first took effect in the European Union in 2006. While it's often called "the lead-free directive," it actually restricts the use of five hazardous substances in addition to lead (Pb). While lead may be hazardous to our health due to improper disposal of lead-containing electronics, of equal concern is the safety and reliability of electronics manufactured with lead-free solders. Solutions must have low resistance and excellent reliability for adoption in future packages. Dow provides lead-free solder-plating chemicals focusing on yield, throughput and reliability.

Over the years, Dow has learned how to remove defects from the solder itself as well as tailor the solder material microstructures to ensure long-term device reliability. For future 3D-TSV packaging, our lead-free SnAg plating chemistry shows excellent compatibility with Cu pillars and Cu TSV.

In addition to the challenges faced with Cu TSV plating, challenges with soldering TSVs or redistribution layers running from TSVs to Cu pillars and micro bumps have been tackled. Remember RoHS, the Restriction of Hazardous Substances Directive? It’s been an ongoing topic of discussion since it first took effect in the European Union in 2006. While it's often called "the lead-free directive," it actually restricts the use of five hazardous substances in addition to lead (Pb). While lead may be hazardous to our health due to improper disposal of lead-containing electronics, of equal concern is the safety and reliability of electronics manufactured with lead-free solders. Solutions must have low resistance and excellent reliability for adoption in future packages. Dow provides lead-free solder-plating chemicals focusing on yield, throughput and reliability.

Over the years, Dow has learned how to remove defects from the solder itself as well as tailor the solder material microstructures to ensure long-term device reliability. For future 3D-TSV packaging, our lead-free SnAg plating chemistry shows excellent compatibility with Cu pillars and Cu TSV.