Uncooled Thermoelectric Infrared Sensor With Advanced Micromachining

A simple mass producible uncooled thermoelectric infrared microsensor has been designed and fabricated. To improve the cost-efficiency, an advanced micromachining process, which combines wet anisotropic pre-etching and XeF₂ dry isotropic post-etching, is adopted for the sensor fabrication. The wet anisotropic pre-etching removes bulk silicon from back-side and forms a thin silicon membrane for device fabrication, the XeF₂ dry isotropic post-etching undercuts silicon membrane and releases the microstructure. Experimental results show that the sensor with advanced micromachining exhibits a two times higher responsivity and detectivity than the sensor with only XeF₂ front-side etching. In air at room temperature, the sensor with advanced micromachining has a responsivity of 71.57 V W^-1, noise equivalent power of 0.64 nW Hz^-1/2, detectivity of 6.21×10⁷ cm Hz^1/2 W^-1 and a time constant of 13.2 ms. The effect of back-side etch window size on sensor performance is also characterized by finite-element method simulation.