Thermal Effects on the Performance Degradation of On-Chip Coplanar Waveguide-Based Passive Semiconductor Devices

The constitutive parameters of most semiconductors, such as silicon and GaAs, are functions of temperature. Hence, the performance of passive and active device fabricated on silicon or GaAs substrate strongly depends on the operating temperature. Although passive devices are not so sensitive to the variation in temperature as active devices do, it is still necessary to examine the thermal effects on the performance degradation of microstripor coplanar waveguide-based passive devices in the injection of high-power signal. To accurately capture the thermal effects on the performance degradation of an onchip passive semiconductor device, the distributed parameters, such as series impedance and shunt admittance, should be modified to be both frequencyand temperature-dependent. In the case of silicon substrate, the doping concentration is a function of temperature, and the temperature coefficient TR C of silicon resistivity varies over a wide range. On the other hand, it should be noted that even the thermal conductivities of silicon, GaAs and InP are temperaturedependent. In this paper, we study the increase in temperature on the performance degradation of some typical coplanar waveguide-based passive devices fabricated on silicon and GaAs substrates, respectively. Over the temperature from C o 25 to as high as C o 145 , and based on the modified frequencyand temperaturedependent distributed circuit models, numerical and experimental results are presented to show: (a) the increase in conductive loss of metallization plane, which further results in the increase in mode attenuation coefficient for uniform finite-ground ground coplanar waveguides; (b) the increase in conductive losses of some coplanar waveguides-based interconnects; and (c) the decrease in performance indicators of some passive devices, such as Q-factor and maximum available gain. Fortunately, the increase in temperature from C o 25 to as high as C o 145 has little effect on the performance of capacitive devices and the electromagnetic coupling between neighboring passive devices, such as two parallel open coplanar waveguides, two inductor and capacitors, etc. These are all demonstrated experimentally.