RF performance of Standard, High-Resistivity and Trap-Rich Silicon substrates down to cryogenic temperature

We investigate the temperature-dependent RF response of different types of silicon substrates (standard, high-resistivity and trap-rich) through measurements performed on BEOL-embedded inductors from room temperature down to 7K. For the first time, we observe that the performance ranking between substrates, well known at 300K, is altered in cryogenic conditions (T<50K). Based on a parametric analysis of the Q-factor, we attribute this behavior to the heightened importance at low T of counteracting a parasitic surface conduction (PSC) forming at the interface between the substrate and the dielectric.