Design of an Embedded Broadband Thermoelectric Power Sensor in the InP DHBT Process

Abstract

The thermopile-based thermoelectric sensor has emerged as an important approach for microwave power measurement. It employs the Seebeck effect, which converts the microwave power into the heat and generates the thermovoltage. However, the output thermovoltage generally exhibits a frequency-dependent feature, which affects measurement accuracy. Besides, the low sensitivity of the current existed planar thermopile-based sensor constrains its further application. This is mainly caused by the heat loss of the substrate in the conversion process of microwave power-heat-electricity. In this paper, a novel embedded power sensor based on the indium phosphide (InP) double heterojunction bipolar transistor (DHBT) process is presented. The thermopile is embedded in the benzocyclobutene (BCB) to prevent the heat loss, and the embedded structure also enables this sensor to eliminate the need for microelectromechanical system (MEMS) technology. The electromagnetic simulation by ANSYS high frequency structure simulator (HFSS) and thermal simulation by ANSYS Steady-State Thermal are combined to evaluate the sensor performance. The result shows that the output voltage increases with the input power linearly, and the proposed sensor is almost independent of the microwave frequency. A sensitivity of l.07 mV/mW has been achieved up to 200 GHz, with the port return loss lower than −15.8 dB.