Radio-frequency (RF) switches based on phase-change materials (PCMs) offer a disruptive alternative to conventional CMOS-based technologies. With their bistable operation (zero power static consumption) and ultra-low Figure of Merit FOM=R_ON*C_OFF (<10 fs), these devices are ideally suited for millimeter-wave (mmWave) applications. They address key challenges such as high data throughput, low power consumption and device miniaturization, making them attractive for telecommunications, IoT, automotive systems, imaging, space observation, and industrial control.

These switches use chalcogenide materials, like GeTe, which can reversibly transition between two phases: a low-resistivity crystalline phase and a high-resistivity amorphous phase. By applying controlled thermal pulses, the material can be toggled between these non-volatile states, switching the RF device between a conductive (ON) and an insulating (OFF) state.

A major milestone has been achieved at CEA-Leti, and in Europe, with the first successful integration of a PCM RF switch on a 300 mm silicon substrate. Even more significantly, this marks the first integration of a PCM RF switch into the back-end-of-line (BEOL) of a 22 nm FD-SOI CMOS industrial platform. Initial electrical tests demonstrate successful switching of the devices between ON and OFF states. Full device characterization is ongoing and will be reported by Q4 2025 as part of the FAMES project.

Until now, PCM RF switches at CEA-Leti were fabricated as standalone devices on 200 mm wafers. Moving to 300 mm wafers enables compatibility with advanced microelectronics manufacturing lines, offering improved equipment performance, increased throughput, reduced production costs and enhanced device performance. This BEOL integration within a CMOS FDSOI platform allows for a direct interconnection between the PCM switch and CMOS components, eliminating the parasitic effects resulting from hybrid assemblies. This monolithic approach significantly improves overall system performance.

The transition from a standalone PCM RF switch integration on 200 mm silicon wafers to a monolithic integration within 300 mm FD-SOI CMOS wafers was enabled by the FAMES pilot line. This breakthrough paves the way for new generations of reconfigurable circuit architectures based on FD-SOI CMOS, particularly to address future communication needs in the sub-THz frequency range.