Tower Semiconductor is using phase-change materials to make non-volatile RF switches – therefore consuming no power to hold open or closed suiting them to battery-powered IoT use.

Tower-Semi

“This switch technology demonstrates a figure-of-merit Ron x Coff <10fs,” according to the company. “The switch performs over frequencies spanning MHz to all frequency bands discussed for 5G, and further into the mmWave.”

Built in a back-end process and intended for high-volume manufacturing, the switches have been integrated onto SiGe BiCMOS and power CMOS – Multi-project wafer runs (MPWs) are planned in 2021.

Little information is public right now – the switches are to be presented at the virtual International Microwave Symposium (IMS 2020) this week as sessions Tu1G-2 and Tu1G-5.

Tu1G-2 will cover a 25THz FCO (6.3fs Ron x Coff) phase-change RF switch that have been cycled over a billion times – built on a 200mm silicon process.

There are two:

• 2.3Ω Ron

       2.7fF Coff
       >6fs FoM
       cycled 1bn times

• 0.82Ω Ron

       7.7fF Coff
       >6fs FoM

“Both layouts show minimal changes to Ron or actuation voltage when cycled 10 million times,” according to the conference abstract.

Tu1G-5 will cover phase-change RF switches on a production SiGe BiCMOS process with RF circuits.

“The monolithic integration of phase-change material RF switches did not impact the performance of the BiCMOS process components, such as FETs and bipolar devices,” according to this papers abstract.

By adding phase-change switches to its SBC18H3B process, Tower built:

• 5bit 32state switched capacitor covering 33fF to 6.75pF in ~215fF steps
• 24.25 to 33.4GHz switched filter using two SPDTs
• 400MHz to 6GHz tunable band-pass filter with seven phase change switches

Applications for the phase change material RF switches are foreseen in mobiles, base-stations and mmWave communications.