What is CoWoS Technology?
When we look at Chip on Wafer on Substrate (CoWoS) technology, we see an innovative way to bridge the gap between traditional 2D designs and true 3D designs. CoWoS is often called a 2.5D solution because, although it stacks components closely, the interposer layer itself doesn’t have any active devices — it’s made purely with back-end-of-line (BEOL) processes.
With CoWoS, we use a silicon interposer with through-silicon vias (TSVs) to create a dense, high-speed connection between the chip dies and the substrate. If you and I were designing a system using true 3D-ICs, we could stack the dies face-to-face, face-to-back, or back-to-back, connecting them with micro-bumps or TSVs depending on the setup. When TSVs are used, we would need to thin the dies to accommodate the vertical connections.
In CoWoS, we benefit from up to three layers of fine copper routing, allowing submicron-level connections between the dies. While CoWoS may not offer the same compactness as true 3D stacking, it gives you and me a major advantage in routing density, delivering memory bandwidth that competes with full 3D solutions. That’s why technologies like High Bandwidth Memory (HBM) often rely on CoWoS to achieve outstanding performance.
Advantage of CoWoS Technology
One of the key benefits you’ll appreciate is how the silicon interposer brings the dies extremely close together — just tens of microns apart — keeping the total wirelength within a few millimeters. This proximity allows us to design systems with lower power consumption because the I/O drivers don’t need termination.
Even though CoWoS doesn’t shrink the design as much as a full 3D-IC, it actually makes power delivery and thermal management easier for you and me. Since there are no active devices on the interposer, we can focus on placing TSVs strategically and even add metal–insulator–metal (MIM) capacitors to fight high-frequency noise and reduce dynamic IR drops.
If you’re looking to build high-performance systems with massive bandwidth and better thermal efficiency, CoWoS is definitely a technology you and I should explore.
