PCB Design Considerations and Temperature Sensing for Cryo-CMOS

This work presents the design considerations of printed circuit board (PCB) and temperature sensing for cryogenic CMOS (Cryo-CMOS) applications. The PCB operates as expected at cryogenic temperatures showing that its structural design and selected materials build a useful support for using it in Cryo-CMOS. The PCB structure includes a thermal bridge made of oxygen-free high conductivity (OFHC) copper, which has demonstrated high efficiency in thermal transfer. For measuring the temperature of the surface of interest a commercial PT100 temperature sensor was used. The electrical test of an on-chip poly-silicon (poly) resistor is assessed for their possible use as a temperature sensor. From experimental results both, the PT100 and poly-resistor, present a residual resistance that was subtracted from the temperature-dependent resistance model in order to know the resistance value at 4 K. For modeling purposes the PT100 sensor was modeled as a series conection of three resistors by following a piecewise linear approach, while the poly-resistor can be described using a second-order polynomial regression.