Solid immersion interference lithography with conformable phase mask

• We propose a simple and cost-effective method of immersion interference lithography.
• It allows close contact with the solid coupling medium without index matching liquid.
• The photoresist is kept free from the contamination of liquid.
• The solid coupling medium improves the resolution by a factor of its refractive index.
• We obtained a 58-nm half-pitch grating, which corresponds to a feature size of 0.18λ.

This study proposes a simple and cost-effective method of solid immersion interference lithography that uses a conformable phase mask. Perfluoropolyether based polymer was used as the material of the elastomeric phase mask. The proposed method requires no liquid layer to function as the coupling medium or the index matching layer and keeps the photoresist free from the contamination of liquid. The solid coupling medium improves the resolution of interference fringes by a factor of its refractive index. This study presents an exposed interference fringe with a half-pitch of 58 nm using a He-Cd laser with λ = 325 nm, which corresponds to a feature size of λ/5.6.

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