In the relentless pursuit of advancing quantum technologies and energy efficiency, a groundbreaking development has emerged from the labs of University Grenoble Alpes, CEA, LETI, Grenoble, France. Led by Candice Thomas, a team of researchers has pioneered a new method for creating fine pitch superconducting interconnects using direct bonding of niobium (Nb) pads. This innovation, detailed in the journal ‘Materials for Quantum Technology’ (translated to English as ‘Materials for Quantum Technology’), promises to revolutionize cryogenic systems and pave the way for large-scale integration in the energy sector.
The challenge of creating superconducting interconnects with micrometer and potentially sub-micrometer pitches has long been a hurdle in the industry. These interconnects are crucial for minimizing signal dispersion, cross talk, and thermal management in cryogenic systems. Thomas and her team have tackled this challenge head-on by developing a wafer-to-wafer direct bonding process for Nb pads. Unlike traditional methods, their approach surrounds the Nb pads with air instead of dielectric material, significantly reducing signal and thermal losses between the wafers.
The research team utilized 200 mm processes, typically used for Cu/SiO2 hybrid bonding and Nb routing levels, to fabricate and characterize these interconnects. The results are impressive: transmission electron microscopy revealed a high-quality bonded interface, and wafer-level parametric tests at 300 K showed a yield exceeding 90%. But the real test came at low temperatures. Electrical measurements in a cryostat demonstrated a critical temperature of 4.6 K, a critical magnetic field of 3.2 T, and a critical current density of 1.25 kA/cm2 at 2 K and 0 T for 10 µm × 10 µm bonded Nb pads.
“Our findings indicate that these interconnects could be a game-changer for cryogenic systems,” Thomas explained. “The ability to achieve such high yields and performance metrics at these scales opens up new possibilities for large-scale integration and energy efficiency.”
The implications of this research are vast. In the energy sector, where cryogenic systems are integral to various applications, from superconducting power transmission to quantum computing, these interconnects could lead to more efficient and powerful systems. The reduced signal and thermal losses mean that energy can be transmitted more effectively, potentially lowering operational costs and environmental impact.
Thomas further elaborated, “The potential for commercial applications is enormous. By improving the efficiency and performance of cryogenic systems, we can contribute to a more sustainable energy future.”
As the industry continues to push the boundaries of what’s possible, this research from University Grenoble Alpes, CEA, LETI, Grenoble, France, stands as a beacon of innovation. The development of fine pitch superconducting interconnects using Nb direct bonding is not just a scientific achievement; it’s a step towards a more efficient and sustainable energy landscape. The future of cryogenic systems and quantum technologies looks brighter than ever, thanks to the pioneering work of Candice Thomas and her team.
