Design and fabrication of a novel crystal SiGeC far infrared sensor with wavelength 8-14 micrometer

In this paper, we report the design, fabrication, and performance of a novel crystal SiGeC infrared sensor with wavelength 8-14 μm by bulk micromachining technology for portable far infrared ray (FIR) in rehabilitation system application. The working principle of the sensor is based on the change of thermistor´s resistance under the irradiation FIR light. The thermistor in the IR detector is made of Si_0.68Ge_0.31C_0.01 thin films for its large activation energy of 0.21 ev and the temperature coefficient (TCR) of -2.74%, respectively. Finite element method package ANSYS has been employed for analyze of the thermal isolation and stress distribution in the IR detector. The dimension of the microbridge fabricated by anisotropic wet etching is 2000 × 2000 × 25 μm³. The developed FIR sensor exhibits the thermal conductance of 1.85 × 10^-1 WK^-1 and the heat capacity as 7.4 × 10^-7 JK^-1 under air ambient at room temperature. The responsivity is 523 VW^-1 in the waveband 8-14 μm with nickel absorber under a bias voltage 1.5 V.