A Millimeter-wave Image Sensor using Antenna Coupled Micro Thermocouple

Summary

A newly developed millimeter wave detector that adopts a micro dipole antenna as a millimeter wave receiver and a micro thermocouple as a bolometer is presented. The micro-thermocouple and a micro heater were designed to be placed between the two arms of dipole antenna. The incident millimeter wave is converted to a voltage signal by the Seebeck effect of the micro-thermocouple. The thermocouple made of aluminum and polysilicon and the heater made of polysilicon were fabricated on the low stress silicon nitride diaphragm to reduce the surface wave loss and to enhance the thermal isolation. A micromachined silicon reflector was used to improve the gain of the antenna. Also for the better impedance matching, the distance from the antenna to reflector was optimized by simulation and measurement technique. The thermal conductance of the device was measured to be 7.9×10^{− 5}W/K at 10mTorr. The measured resonance frequency was 44GHz and the maximum responsivity was 7.5V/W. The device showed the operating bandwidth of 40∼50GHz for 3dB sensitivity.