Elimination of stress-induced curvature in microbolometer focal plane arrays

The paper reports a disruptive engineering approach to eliminating stress-induced curvature in cantilever-based microbolometer focal plane arrays (FPAs). Using a combination of ion beam machining and rapid thermal annealing (RTA), we successfully modified the curvatures of free-standing SiN_x/Al bimaterial cantilever structures for microbolometer applications. The ion beam machining changes the surface, either by ion implantation or surface sputter etching; the RTA changes the residual stresses in bimaterials and thus modifies the FPA curvatures. Proof-of-concept experiments have shown that it is possible to achieve "flat" microbolometer structures by using these two techniques.