  This paper presents the characterization of microwave passive components,
including metal-oxide-metal (MoM) capacitors, transformers, and resonators, at
deep cryogenic temperature (4.2 K). The variations in capacitance, inductance
and quality factor are explained in relation to the temperature dependence of
the physical parameters and the resulting insights on modeling of passives at
cryogenic temperatures are provided. Both characterization and modeling,
reported for the first time down to 4.2 K, are essential in designing cryogenic
CMOS radio-frequency integrated circuits, a promising candidate to build the
electronic interface for scalable quantum computers.
