In the last decade, the semiconductor industry has undergone a quiet revolution. While most people keep their eyes on transistor sizes — like 7nm, 5nm, and now 3nm — another equally critical evolution has been happening above the wafer: advanced packaging. Among the standout technologies driving this change is what the industry calls CoW, especially in the form of TSMC’s CoWoS (Chip on Wafer on Substrate).

So what exactly is CoW? How does it differ from CoWoS? What is EMIB, and how do all these technologies compare in profitability and business strategy? Let’s break it down.

What is CoW?

At its simplest, CoW stands for "Chip on Wafer." It refers to processes where multiple chiplets (or dies) are placed directly on a wafer (or interposer wafer) before further processing.

Historically, chips were diced off a wafer and then individually packaged. But modern designs need enormous bandwidth and tightly integrated components that can't be achieved just by linking chips on a circuit board. CoW approaches allow manufacturers to place multiple dies side by side on a wafer surface, creating dense, fast interconnects before the assembly is moved to a larger substrate. This enables much higher data rates, shorter signal paths, and more compact systems.

How does CoWoS work?

CoWoS is a 2.5D packaging technology that uses a large silicon interposer. Here’s how it works:

1. Multiple chips (dies) — such as CPUs, GPUs, ASICs, or HBM memory stacks — are mounted side by side on top of a thin silicon interposer wafer. This is the "Chip on Wafer" stage.
2. The interposer acts as a high-density wiring layer, routing thousands of fine signals between these dies. Because it’s silicon, it can be manufactured with much tighter wiring pitches than a typical organic substrate.
3. This wafer-level assembly is then attached to a larger organic package substrate, which connects it to the motherboard or system — the "on Substrate" stage.

This approach allows chip designers to build huge, high-bandwidth systems that go far beyond what a single monolithic chip could achieve. For instance, NVIDIA’s A100 and H100 GPUs use CoWoS to link GPU dies with HBM memory, achieving data transfer rates over 1 TB/s — critical for training today’s massive AI models.

What is EMIB?

EMIB, short for "Embedded Multi-die Interconnect Bridge," is Intel’s alternative 2.5D advanced packaging approach. Unlike CoWoS, which uses a large silicon interposer that sits under multiple chips, EMIB embeds tiny silicon bridges directly into the organic package substrate. These bridges are positioned only where high-speed connections are needed between chiplets.

Why is EMIB different?

1. There’s no full silicon interposer. Instead, small silicon pieces with fine wiring are placed just under the edges of adjacent dies.
2. This significantly reduces cost and complexity compared to a full-size interposer.
3. It still provides very high bandwidth connections where needed, with less added capacitance and simpler thermal management.

Intel has used EMIB in shipping products like Stratix 10 and Agilex FPGAs, Ponte Vecchio GPUs, Sapphire Rapids Xeons with HBM, and new Meteor Lake CPUs. It also plans to advance to EMIB T, which integrates TSVs for even more power delivery and bandwidth — aimed at next-gen AI accelerators using HBM4 and UCIe.

Profitability: CoWoS vs EMIB

From a business point of view, advanced packaging like CoWoS and EMIB is critical not just for technical reasons, but because it offers much higher margins than traditional packaging or even many mature wafer nodes.

1. CoWoS profitability: TSMC has reported that its advanced packaging businesses (dominated by CoWoS and InFO) have grown to reach margins close to its core foundry operations, around 30-45%. This is driven by strong demand for AI and HPC chips that require HBM and massive bandwidth, paired with very limited alternative suppliers. The high average selling prices and relatively moderate additional capital needed compared to a new EUV wafer line mean CoWoS has become a profit engine for TSMC.
2. EMIB profitability: Intel’s EMIB and EMIB T are expected to follow a similar path. EMIB started around break-even but is forecasted to reach margins around or above 40% by 2030, driven by improved yields, growing volume, and the fact that it’s essential for ultra-high-performance products. Because there are only a few providers of such high-density advanced packaging, Intel has strong pricing power, allowing it to command premium prices.

Structurally, this is why both CoWoS and EMIB sit in a sweet spot: they have lower capex intensity than cutting-edge wafer fabs, faster yield ramps, and are priced as critical enablers for system performance — all of which contribute to high margins.

Why does this matter for the industry?

As Moore’s Law slows down, it’s getting harder and more expensive to pack everything into one gigantic monolithic die. Advanced packaging like CoWoS and EMIB is the answer. It lets chip designers:

1. Break designs into smaller chiplets, improving yields and lowering cost.
2. Mix process nodes, like pairing a 5nm compute tile with a 16nm I/O controller on the same package.
3. Build beyond reticle limits, since they aren’t constrained by the maximum size a single photolithography exposure can cover.

This is why the industry is shifting from SoC (System on Chip) to SoP (System on Package). The package itself becomes the true integration point for high-performance computing.

In summary

CoW is the broad concept of placing chiplets directly on wafers.

CoWoS is TSMC’s powerful 2.5D implementation that uses a large interposer to connect dies with ultra-high bandwidth — essential for AI GPUs and supercomputing.

EMIB is Intel’s alternative, embedding tiny silicon bridges only where needed, cutting costs while still achieving high-speed links. Both technologies are not only technical marvels but also critical for profitability. They allow foundries and IDMs to capture high-margin business by enabling the next generation of data center and AI workloads.

References

1. TSMC earnings reports and investor calls on advanced packaging profitability
2. Intel investor meetings discussing EMIB and EMIB T margins and forecasts
3. TechInsights and SemiAnalysis articles on CoWoS and EMIB yield ramps
4. IEEE papers on embedded bridge vs interposer electrical performance
5. Market analysis from Yole Développement on advanced packaging market growth
6. Coverage from EE Times, Tom’s Hardware, AnandTech, and EDN on specific product implementations