(Color online) Schematic outline of the process flow: (a) Deposition of the mask layers for lithography and etching, (b) pattern definition by lithography and removing of developed photoresist, (c) pattern transfer into first and ARC layers by RIE, (d) definition of hole diameter by plasma ashing of the ARC, (e) pattern transfer into the second and Cr hard mask by RIE, (f) final etching of Ta by DRIE.
Scanning electron micrographs of the fabrication steps for the Ta PhC: (a) developed photoresist after IL, (b) lithography layers ( and ARC) etched by RIE, (c) and (d) definition of hole diameter by plasma ashing of the ARC, (e) and (f) pattern transfer into Cr hard mask by RIE. (Cross sections are taken of a cleaved Si control sample for the presented fabrication steps, which do not depend on the substrate material.)
(Color online) (a) and (b) Scanning electron micrographs of fabricated Ta PhC obtained by chemical wet etch and dry etch (RIE) of the Cr mask, respectively. (c) Simulation of the emissivity for a Ta PhC with perfect structure (solid line) and increasing sidewall roughness characterized by the maximum deviation (dashed-dotted line) comparable to the PhC fabricated by wet etch with the measured emissivity (crosses), and simulation with (dashed line) resulting in breaking sidewalls.
Scanning electron micrographs of fabricated Ta PhC showing excellent fabrication accuracy and long range fabrication uniformity. Left insets: Close-up of etched cavities (with remaining Cr mask on top). Right inset: Cross-sectional view of the etched Ta PhC.
(Color online) Measured room temperature emissivity of fabricated Ta PhC on 2 in. substrate measured in the center and towards the edge of the sample (solid lines) as compared to simulation (dashed line) and measured emissivity of flat Ta. Left inset: Schematic PhC structure. Right inset: Digital photo of the full 2 in. diameter sample after etching of the Cr hard mask; crosses indicate approximate measurement positions (scale is in cm).
Parameters used in RIE etch steps.
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