Projecting high depth-to-width aspect ratio of nanolithography with a four-layer metallic waveguide structure

The depth-to-width aspect ratio of pattern engineering by surface plasmons is limited for its field intensity exponential attenuation property. We here report a method to enhance patterns’ aspect ratio with a mask–photoresist–dielectric–metal four-layer metallic waveguide structure. The parameters, index and thickness, of the dielectric layer are discussed and analyzed to illustrate their affection to the patterns’ resolution and aspect ratio. A small thickness of dielectric with its index higher than photoresist will enhance the resolution and aspect ratio of pattern by these proposed structures. Numerical simulation results show that 40 nm half-pitch and 100 nm depth patterns could be performed by a chromium mask with period of 160 nm at the wavelength of 365 nm.