Silicon stencil masks for masked ion beam lithography proximity printing

Abstract

Silicon membranes with 2 μm to 6 μm thickness and ≈ 10×10 mm2 mask field have been fabricated with the help of electrochemical etch stop techniques. The Si foil was coated with 0.3 μm thick PECVD Si3N4. Shaped electron beam lithography was done in ARCH (OCG) positive resist. RIE etching into the nitride layer was done with CHF3/Ar/SF6. Silicon trench etching was based on Cl2/Ar/BCl3 plasma chemistry implementing gas chopping. Ion beam proximity printing of the Silicon stencil mask structures was done with 55 keV Helium ions into 0.4 μm thick AZ PN114 negative resist using the Alpha ion projector of the Society for the Advancements of Microelectronics in Austria in the MIBL (Masked Ion Beam Lithography) mode. Pattern transfer of a mask feature of less than 100 nm diameter (25:1 aspect ratio in the stencil mask) could be demonstrated even for a mask to wafer gap of 1 mm. The prospects of fabricating large area (> 100×100 mm2) Silicon stencil masks for MIBL printing of gate levels for FieldEmitterDisplays (FEDs) andMicro-Electro-Mechanical-Systems (MEMS) is discussed.