A miniaturized thermopneumatic infrared detector with capacitive read-out circuit

摘要

In this paper we present an improved design of a miniaturized thermopneumatic infrared detector withrncapacitive read-out circuit. The hybrid assembly basically consists of a sealed cavity and a capacitiverndisplacement transducer fabricated with silicon micromachining. The IR absorber is placed on a thin,rnfree-standing silicon nitride membrane centrally arranged in the cavity. The very small capacitancernchanges are measured with an extremely sensitive 24-bit sigma-delta converter capable of detectingrncapacitance changes of a few aF. As a result, a responsivity of 714 aF/μW and a specific detectivity ofrn1.3 · 10~6 cm Hz~(1/2) W~(-1) were attained. Further improvements in performance can mainly be achieved byrnreducing the electrode gap of the capacitive displacement transducer.