Arrays of SiO2 substrate-free micromechanical uncooled infrared and terahertz detectors

Abstract

We describe the design, fabrication, and characterization of arrays of uncooled infrared and terahertz micromechanical detectors that utilize SiO2 as a main structural material. Materials with highly dissimilar coefficients of thermal expansion, namely, Al and SiO2, were used to form folded bimaterial regions. This approach improved the detector sensitivity by 12 times compared to SiNx-based detectors of similar shape and size. Two types of structural SiO2 layers were investigated: thermally grown and plasma-enhanced chemical-vapor-deposited SiO2. Fabrication of the detector arrays relied on a straightforward process flow that involved three photolithography steps and no wet etching. The noise equivalent temperature difference intrinsic to the detectors fabricated during this work can reach 3.8 mK when excluding any contribution from the optical readout used to interrogate the arrays.