Evidence of Tunneling Driven Random Telegraph Noise in Cryo-CMOS

CMOS technologies operating at cryogenic temperatures play a key role in the successful deployment of quantum computers. While tremendous efforts have been devoted to understanding the device electrostatics, there is a lack of studies on the device performance degradation mechanisms, as for instance bias temperature instability (BTI), in cryogenic environments. To study BTI, typically large-area devices are characterized. However, as we demonstrate, when approaching the cyrogenic temperature regime, the investigation of single defects becomes necessary. Using single defect measurements, we show that even at 4 K, there are active defects causing random telegraph noise (RTN). We can explain the temperature dependence of the charge transfer mechanism by nuclear tunneling in the framework of the nonradiative multi-phonon (NMP) model. Our measurements and simulations indicate that interface defects are responsible for RTN at cryogenic temperatures. Due to their small relaxation energies and displacements during charge transitions, interface traps have high charge transition rates and do not freeze out, thus playing a crucial role for a high-performance operation of noise-sensitive circuits in cryogenic environments.