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Belgian research hub Imec has taken another step toward high-frequency chiplet-based systems, extending its 300mm RF silicon interposer platform to support system-level integration of III-V chiplets with Si-CMOS technology. The development targets emerging mmWave and sub-THz wireless applications, as well as high-speed signal handling for next-generation data centers.

The latest advances combine high-density embedded capacitors, a scalable passive-component modeling framework, and laser-assisted bonding technology for III-V chiplet assembly. Together, these technologies are designed to improve performance while reducing the cost and complexity of heterogeneous integration.

For eeNews Europe readers working on RF design, advanced packaging and semiconductor manufacturing, the announcement highlights practical approaches to integrating III-V materials such as InP, GaAs and GaN with mainstream CMOS platforms. It also offers insight into how chiplet architectures are evolving to address performance bottlenecks in both communications and data-center infrastructure.

Higher-density passives for smaller chiplets

As wireless systems move to ever higher frequencies, designers face growing challenges in balancing performance, power consumption, footprint and manufacturing costs. Imec’s approach keeps performance-critical functions inside compact III-V chiplets while moving passive components onto a silicon interposer with low-loss interconnects.

One of the key additions is a new metal-insulator-metal capacitor (MIMCAP) architecture. The design combines a high-k aluminum-hafnium-oxide dielectric with three-dimensional oxide-stud structures in the back-end-of-line process.

“A key lever to reduce III-V chiplet size and cost is the offloading of passive components – such as decoupling capacitors – onto the RF silicon interposer,” said Xiao Sun. “In a paper presented at this year’s IMS/RFIC conference, we demonstrate how combining this offloading approach with a new MIMCAP architecture enables a 10-to-100-fold increase in capacitance density compared to typical on-chip capacitors in III-V technologies. This supports more compact and cost-efficient system designs and improves power delivery for mmWave and sub-THz wireless systems as well as high-speed data center applications.”

According to Imec, the increase in capacitance density could significantly reduce chiplet area while improving overall system efficiency, particularly for advanced wireless and optical interconnect applications.

Modeling and bonding advances

Complementing the capacitor technology, Imec has introduced a modeling framework for RF interposer passive components, validated up to around 300 GHz. The framework enables designers to predict circuit performance across different geometries without having to repeatedly re-simulate or measure every design variation, helping to reduce development time.

The framework currently focuses on transmission lines, but Imec plans to expand it into a broader design library that will also include inductors and MIM capacitors.

On the assembly side, Imec has demonstrated laser-assisted bonding for integrating III-V chiplets onto the RF silicon interposer. The technique allows chiplets to be mounted on complex passive-rich stacks while avoiding damage to temperature-sensitive layers and maintaining low thermal budgets.

The process achieved alignment accuracy better than 600nm and rotational misalignment below 0.05° across 43 devices. RF measurements after assembly showed reflection below −15 dB in the 110 GHz to 170 GHz range, indicating that chiplet performance is preserved during the bonding process.

Toward manufacturable chiplet-based RF systems

The latest work builds on earlier milestones from Imec. In 2024, the organization demonstrated InP chiplet integration on a 300mm RF silicon interposer with negligible insertion loss at 140GHz. In 2025, it extended the platform’s low-loss performance to 325GHz.

“With this work, we demonstrate a uniquely integrated platform that brings together performance, scalability, and manufacturability. Our next priority is to further advance the platform’s technology readiness, and to enable support for low-volume manufacturing – helping our partners more easily develop and scale next-generation RF systems,” said Sun.

By combining passive integration, predictive design tools and advanced assembly techniques on a single platform, Imec is positioning its RF silicon interposer technology as a potential foundation for future mmWave, sub-THz and high-speed data-center systems.

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