Theoretical study on fabrication of sub-wavelength structures via combining low-order guided mode interference lithography with sample rotation

Guided mode interference lithography based on a symmetric metal-cladding dielectric waveguide structure (a resist between two metal layers), is studied. The low-order guided modes in the waveguide structure excited by 325 nm laser, and then sub-wavelength gratings with half-periods of 47 nm ( λ /6.91) and 60 nm ( λ /5.42) can be obtained by excited TM0 and TE0 guided modes, respectively. Among them, the period of the sub-wavelength grating fabricated by TM0 guided mode interference is smaller, but it is limited by the thickness of resist. TE0 guided mode interference is more suitable for thick resist. On this basis, taking TM0 guided mode as an example, periodic sub-wavelength structures, such as square lattice and quasi-hexagonally close-packed structure, can be obtained by rotating and exposing the sample in different ways. The proposed method of combining guided mode interference lithography with sample rotation has simple operation and low cost, and provides a theoretical reference for fabricating two-dimensional sub-wavelength structures.