Researchers at Seoul National University have developed what they claim to be the world’s first Reconfigurable Intelligent Surface (RIS) manufactured using a standard semiconductor foundry process. This should help advance the upcoming 6G technology and infrastructure.
In a paper published in Nature Communications, the authors introduce STARE, or Semiconductor Transmit Array with Reconfigurable Elements.
“Although numerous studies have advanced 5G communication technologies based on mmWave frequencies, commercialization remains challenging due to the cost and fabrication complexity of cellular infrastructure, including base stations and relays,” the article reads.
The researchers say that they needed to overcome three main challenges brought by the current technology: Current systems rely on liquid crystals, discrete PIN diodes, or varactors mounted onto printed circuit boards, and these materials delay response times due to their nature or how complex it is to assemble surfaces.
Instead of making a circuit board and pasting thousands of separate components onto it, they figured out how to print the entire smart surface—antennas, switches, and routing—directly onto a single silicon wafer in one parallel semiconductor run.
The team built a 4-inch prototype wafer embedding 45 unit cells and 180 custom SODs, testing it in an anechoic chamber. The prototype operated in the upper-mid 6G spectrum at 15.5 GHz. It achieved robust 180° phase control (1-bit resolution), and successfully steered wireless beams dynamically from -45° to +45°.
According to the paper, the researchers achieved nanosecond-level switching speeds, outperforming liquid-crystal methods.
Innovations to Enable 6G
The authors came up with three main solutions to overcome the technological hurdles preventing the RIS breakthrough.
The first was the introduction of a custom selective overlap diode directly inside the silicon. By fixing the internal spacing at 10 micrometers and adjusting the metal layers on top, they perfectly balanced low “ON” resistance with tiny “OFF” capacitance.
They also eliminated the need to send signals using Through-Silicon Vias (TSVs), “reducing fabrication complexity and substrate-induced losses while enabling efficient signal transfer through magnetic coupling.”
Finally, the researchers used high-resistivity silicon wafers, effectively neutralizing the silicon absorption and allowing the waves to transmit efficiently.
Beyond this proof of concept, STARE provides a scalable path toward large-aperture, energy-efficient, and cost-effective RIS implementations compatible with semiconductor foundry processes, offering new opportunities for high-performance beamforming in next-generation wireless systems,” the article concludes.
This article was written with the assistance of AI
