A double-sacrificial-layer uncooled infrared microbolometer in a standard CMOS process

This paper reports the implementation of a low-cost double-sacrificial-layer uncooled infrared microbolometer in a standard 0.5 µm CMOS process, where the CMOS metal interconnect layer is used as the infrared sensitive material. The microbolometer can be created by simple surface sacrificial layer technology after the CMOS fabrication, without any additional lithography and infrared sensitive material deposition. Two surface sacrificial layers are employed by the CMOS metal interconnect and the metal plug. The CMOS metal interconnect is composed of Aluminum material which has a TCR of 0.385%/K. The low-cost microbolometer has a pixel size of 65 µm×65 µm and a fill factor of 29%. Measurements show that the thermal conductance is 1.95×10−6 J/K, the thermal time is 5.27 ms, and the responsivity is 1536 V/W at 10Hz chopper frequency. The total measured rms noise of the microbolometer is 0.732µV for a 10 kHz bandwidth, resulting in a detectivity D* of 8.37×108 cmHz1/2/W.