Unpackaged infrared thermoelectric microsensor realised on suspended membrane by silicon technology

In this article, infrared thermoelectric microsensors manufactured by CMOS technology with an original design are presented. Packaging is not required because absorbing and reflecting superficial zones, laid on a single membrane, are symmetrically structured with regard to the thermal disturbances of the surrounding gas. An analytical model was developed to determine the geometrical parameters of these microsensors in the aim to optimise the sensitivity to the radiation and the immunity to the ambient air temperature variations. Some sensors with membranes areas varying from 3 mm × 3 mm to 10 mm × 10 mm and 3 × 3 and 5 × 2 unpackaged arrays of microsensors were fabricated. A prototype of imager equipped with a polyethylene Fresnel lens was realised. Such devices open the way to a wide range of low resolution–low cost imager applications.