Characterization of mutual heating inside a SiGe ring oscillator

This paper reports on the electrical and thermal characterization of a state of the art SiGe ring oscillator (RO) with 2.2 ps gate delay fabricated in a Si/SiGe:C technology featuring f_T and f_max of ~300 GHz and ~400 GHz, respectively. The transistor model is verified through DC and RF characteristics taken from the same die as the circuit measurements. Excellent agreement between measurements and compact model simulation is shown. A simple method is presented that calculates the nonlinear circuit temperature rise in the local circuit area resulting from mutual heating of all active and passive components. Once taken into account the circuit temperature, the accuracy of circuit simulation is significantly improved.