  Solid-state qubit manipulation and read-out fidelities are reaching
fault-tolerance, but quantum error correction requires millions of physical
qubits and thus a scalable quantum computer architecture. To solve signal-line
bandwidth and fan-out problems, microwave sources required for qubit
manipulation might be embedded close to the qubit chip, typically operating at
temperatures below 4 K. Here, we perform the first low temperature measurements
of a 130 nm BiCMOS based SiGe voltage controlled oscillator. The device
maintains its functionality from 300 K to 4 K. We determined the dependence of
frequency and output power on temperature and magnetic field up to 5 T and
measured the temperature influence on noise performance. While the output power
tends to increase, the frequency shift is 3 % for temperature and 0.02 % for
the field dependence, respectively, both relevant for highly coherent spin
qubit applications. We observe no improvement on output noise, but increased
output flickering.
