Nanoscale lithography with visible light: optical nonlinear saturable absorption effect induced nanobump pattern structures.

Industrial approaches to improve lithographic resolution usually rely upon short-wavelength laser or charged particles of even shorter wavelengths. However, nanoscale lithography with visible light is more effective for practical applications because of its low cost, easy operation, and so on. In the current work, a technical scheme for the optical nonlinear saturable absorption effect to induce nanobump pattern structures is proposed. The theoretical simulation indicates that the spot size can be squeezed and reduced to about 1/12 the original spot size using Si thin films as a nonlinear saturable absorption material, and GaN semiconductor diode as the laser source. The high-density digital versatile disk tester was used as the direct laser writing apparatus to verify the technical scheme. Nanostructures with a size of ∼80 nm were obtained. This size is ∼1/10 the spot size at optical diffraction limit.