A 100-GHz CMOS-Compatible RIS-on-Chip Based on Phase-Delay Lines for 6G Applications

On-chip reconfigurable intelligent surfaces (RIS) are expected to play a vital role in future 6G communication systems. This work proposed a CMOS-compatible on-chip RIS capable of achieving beam steering for the first time. The proposed unit cell design is a combination of a slot, a phase-delay line with VO2, and a ground. Under the two states of the VO2, the unit cell has a 180 deg phase difference at the center frequency, while maintaining reflection magnitudes better than -1.2 dB. Moreover, a 60by60 RIS array based on the present novel unit is designed, demonstrating the beam-steering capability. Finally, to validate the design concept, a prototype is fabricated, and the detailed fabrication process is presented. The measurement result demonstrates a 27.1 dB enhancement between ON and OFF states. The proposed RIS has the advantages of low loss, CMOS-compatibility, providing a foundation for future 6G applications.