Uncooled infrared detector based on silicon diode Wheatstone bridge

Abstract

In this paper, uncooled infrared detector based on silicon diode Wheatstone bridge is studied. Four identical temperature sensing elements made of several diodes in series are designed and fabricated with 2 μm feature size, among which two of them are suspended over the substrate through supporting legs, while the other two are on the substrate. By connecting these four temperature sensing elements in Wheatstone bridge's form, we expect to reduce output noise of the infrared detector for differential output. The tested noise of the infrared detector is 1.24 μV, which is reduced by 58 % comparing to the detector constructed by one suspended temperature sensing element of the Wheatstone bridge. The measured sensitivity and noise equivalent temperature difference (NETD) of the infrared detector are 7.90 μV/K and 0.16 K, respectively. This infrared detector has potential of reaching a NETD in the milli-Kelvin range by using CMOS process with better feature size and pixels containing two supporting legs instead of four supporting legs.