Fabrication of low-stress silicon stencil masks for ion beam lithography

This paper describes the fabrication of stencil masks in large area, low-stress (10 MPa), n-type silicon membranes for demagnifying (4×) ion projection lithography (IPL) and proximity printing. The projection masks have a silicon foil area 95 mm in diameter, thicknesses between 2 and 5 μm, and resolution of 0.6 μm. Proximity printing masks have a 1 cm square membrane area, 0.8 μm thickness, and 80 nm resolution. Measured distortion (3σ) in the IPL masks ranges between 0.23 and 0.65 μm, with an experimental error of 0.20 μm.