What is advanced chip packaging (CoWoS)?
Advanced chip packaging places several chips close together in one package, with the aim of making them work like a single large chip. CoWoS, short for Chip on Wafer on Substrate, is TSMC's version and is widely used for AI processors.
Also known as: CoWoS, Chip on Wafer on Substrate, 2.5D packaging
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How it works
The U.S. National Institute of Standards and Technology (NIST) uses the term advanced packaging for assemblies of many chips with different functions. It says they sit close together on a shared base, or substrate, in two or three dimensions and at very fine scale. NIST says this yields performance and power savings well beyond conventionally packaged chips on a circuit board.
CoWoS is TSMC's implementation. As TSMC describes it, processor chips and stacks of high-bandwidth memory are mounted on an interposer, a layer of wiring that links them. The company offers three variants. CoWoS-S uses a silicon interposer and has been in production since 2012. CoWoS-R, in volume production since 2023, uses an interposer made of polymer and copper traces, known as a redistribution layer. CoWoS-L, in volume production since 2024, combines a redistribution-layer interposer with small embedded silicon chips that carry high-density connections between chips. TSMC lists a maximum silicon interposer of about 2,700 square millimeters for CoWoS-S. It recommends the other two for larger designs.
Why it matters
NIST states that recent advances in artificial intelligence would not be possible without advanced packaging. In April 2026 Reuters described modern AI chips, such as Nvidia's, as several chips joined by advanced packaging. It called that step a supply bottleneck. TSMC says demand for CoWoS grew after generative AI arrived in late 2022.
CoWoS is not the only option. Reuters reported in May 2026 that CoWoS is widely used for AI chips, including Nvidia's. It said Intel's EMIB is a competing technology and that chip designer MediaTek said it supports both.
Where things stand in 2026
The same April 2026 Reuters report said many chips made at TSMC's Arizona factory must go back to Taiwan for packaging. TSMC executives said that month that construction of an Arizona packaging plant had begun. One told Reuters the goal is CoWoS capability there before 2029. Reuters added that Amkor Technology said in 2025 it planned an Arizona packaging factory starting production by early 2028.
In July 2026, TSMC pledged a further $100 billion for Arizona. Its chief executive said the additional plants would probably include advanced packaging. Analysts cited by Reuters said demand for CoWoS remained strong. In September 2026 Taiwan broke ground on an advanced packaging industrial park in Kaohsiung. There, TSMC plans a validation laboratory and a training center expected to open in late 2029.
Sources
- National Advanced Packaging Manufacturing Program, National Institute of Standards and Technology (NIST)
- CoWoS® - Taiwan Semiconductor Manufacturing Company Limited, Taiwan Semiconductor Manufacturing Company (TSMC)
- TSMC plans to open chip packaging plant in Arizona by 2029, executive says, Reuters
- Taiwan's MediaTek says it supports both TSMC and Intel's advanced packaging technologies, Reuters
- TSMC to invest another $100 billion in US as Q2 profit blows past forecasts, Reuters
- Taiwan breaks ground on advanced packaging park anchored by TSMC, Reuters
