Temperature Stability and Reliability Aspects of 77 GHz Voltage Controlled Oscillators in a SiGe:C BiCMOS Technology

The factors determining the temperature stability of a 77 GHz voltage controlled oscillator (VCO) and reliability issues of the SiGe:C hetero bipolar transistors (HBT) used in the VCO are studied. The VCO with output buffer and NMOS varactors shows an output power of +14.6 dBm at 77 GHz. In the temperature range up to 125degC we get a low oscillation frequency shift Deltaf_osc = -1.2 GHz/100 K. Although the HBTs used for the VCO show significant base current degradation during high and low temperature stress, their rf and low-frequency noise behavior, relevant for VCO reliability, is not affected.