Silicon-Supported Membranes for Improved Large-Area and High-Density Micro/Nanostencil Lithography

In this paper, the fabrication and use of stencils for full-wafer scale shadow mask (stencil) lithography is described. The stencils fabricated via microelectromechanical systems are mechanically stabilized and show clearly reduced stress-induced membrane deformation, which translates into a more accurate surface pattern definition. Solid-state SiN membranes 500 nm thick and up to 1 mm² in size having a 20-mum-thick silicon support rim following the outline of the stencil apertures were fabricated in a 100-mm Si wafer. The minimum aperture size presented in this paper is 3 mum. The increase of membrane stability was confirmed by depositing a highly stressed 35-nm-thick chrome layer. The results demonstrate a stability increase of the Si-supported compared to nonsupported membrane with identical shape by up to 89% as measured by the reduced out-of-plane deflection of overhanging membrane sections. Comparison by scanning electron microscopy and atomic force microscopy of the resulting micropatterns obtained by Cr deposition through both unsupported and Si-rim supported stencils shows better edge sharpness and clearer spatial details for surface patterns deposited through the stabilized stencil compared to those deposited through the nonsupported stencil. The improved stabilized stencils allow for large-area high-density surface patterning while maintaining membrane stability and pattern definition during stencil lithography