Optical connectivity – and silicon photonics in particular – is expected to be a key technology for enabling connectivity for next-generation data centers, especially those designed for HPC applications. With ever-increasing bandwidth requirements to maintain system performance (and keep scaling), copper signaling simply won't be enough to keep up. To that end, several companies are developing silicon photonics solutions, including fab suppliers like TSMC, which this week outlined its 3D optical engine roadmap as part of its 2024 North American Technology Symposium. presented, presenting its plan to bring optical connectivity up to 12.8 Tbps. TSMC-fabbed processors.

TSMC's Compact Universal Photonic Engine (COUPE) stacks an electronics integrated circuit on a photonic integrated circuit (EIC-on-PIC) using the company's SoIC-X packaging technology. Foundry says its use of SoIC-X enables the lowest impedance at the die-to-die interface and hence the highest energy efficiency. The EIC itself is manufactured on a 65nm class process technology.

TSMC's 1st Generation 3D Optical Engine (or COUPE) will be integrated into an OSFP pluggable device operating at 1.6 Tbps. This is a transfer rate well ahead of current copper Ethernet standards – which top out at 800 Gbps – underscoring the immediate bandwidth benefit of optical interconnects for heavily networked compute clusters, at the expected power savings. Don't mind.

Looking further ahead, the 2nd generation of COUPE is designed to be integrated into CoWoS packaging as co-packaged optics with a switch, bringing optical interconnections to the motherboard level. This version COUPE will support data transfer rates up to 6.40 Tbps with lower latency than the earlier version.

TSMC's third iteration of COUPE – COUPE running on the CoWoS interposer – is likely to take things a step further, increasing transfer rates to 12.8 Tbps while bringing optical connectivity closer to the processor itself. Currently, COUPE-on-CoWoS is in the exploration phase of development and TSMC does not have a set target date.

Ultimately, unlike many of its industry peers, TSMC has not yet entered the silicon photonics market, leaving it to players like GlobalFoundries. But with its 3D optical engine strategy, the company will enter this key market as it looks to make up for lost time.

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