Fabrication of long-range surface plasmon hydrogen sensors on Cytop membranes integrating grating couplers

The fabrication process for a long-range surface plasmon polariton hydrogen sensor is presented. The device, referred to as the cladded membrane waveguide, features a 5 mu m wide and 20 nm thick gold stripe embedded in a 160 nm free standing Cytop membrane. Broadside excitation and output are achieved with integrated grating couplers. Hydrogen sensitivity is provided by an overlaid 5 nm thick palladium patch, which acts as a transduction medium. The device is fabricated by integrating several process techniques including blind through-wafer alignment, optical photolithography, overlaid electron beam lithography, metal lift-off, and through-substrate silicon wet etching. Fabricated results are presented along with a detailed discussion. The devices are characterized optically via a cutback measurement with the measured waveguide attenuation being consistent with simulated values. (C) 2015 American Vacuum Society.