TSMC Turns to GlobalFoundries for CoWoS Interposer Supply

TSMC has started working with GlobalFoundries to supply interposers for its CoWoS advanced packaging flow, according to a report by EE Times Asia. The arrangement pairs two foundries that compete directly for wafer orders and redirects part of the CoWoS supply chain outside TSMC's own fabs.

The subject of the report is TSMC's CoWoS (Chip-on-Wafer-on-Substrate) packaging technology, which stacks logic dies and high-bandwidth memory on silicon interposers. Interposers — the passive silicon layers that carry connections between dies and the substrate — have become a capacity bottleneck as demand for AI accelerators grows.

What does the GlobalFoundries arrangement cover?

EE Times Asia identifies interposers as the specific component TSMC is sourcing from GlobalFoundries. Interposers carry fewer process requirements than the logic wafers TSMC builds at its leading-edge nodes, which allows a trailing-edge foundry to manufacture them.

Key elements of the arrangement as reported:

• TSMC uses GlobalFoundries as an interposer supplier for CoWoS packaging.
• CoWoS packaging connects compute dies and memory stacks on a silicon interposer.
• The move follows sustained demand pressure on TSMC's own CoWoS capacity.

The report frames the deal as a capacity measure: TSMC adds interposer supply without converting its own leading-edge wafer lines to a lower-value component.

Why outsource interposers rather than build more in-house?

Interposers do not require the most advanced transistor nodes, so they occupy wafer capacity that TSMC can otherwise sell at higher margins for logic production. GlobalFoundries, which exited the leading-edge race years ago, runs fabs suited to this class of silicon.

For GlobalFoundries, the arrangement adds a customer at a volume scale tied to AI accelerator output. For TSMC, it adds interposer supply at a time when CoWoS output sets the shipment ceiling for AI chips built on its process technology.

The two companies remain competitors for foundry business in general. This deal covers one component within one packaging flow, not a broader manufacturing alliance.

What does this mean for AI chip supply?

CoWoS capacity has constrained shipments of the large accelerators that depend on it. Any addition to interposer supply — the layer EE Times Asia names as the outsourced piece — feeds directly into how many packaged devices TSMC can ship per quarter.

The arrangement signals how TSMC now treats advanced packaging capacity: as a constraint worth solving through external suppliers, including a direct foundry rival. Read the full EE Times Asia report for the technical and sourcing details.

One sentence: TSMC is buying CoWoS interposers from GlobalFoundries, and that supply line now sits inside the AI chip output equation.