Near-field Optical Nanolithography Research Articles

Continuous phase-shift lithography with a roll-type mask and application to transparent conductor fabrication

We report the development of a near-field optical nanolithography method using a roll-type phase-shift mask. Sub-wavelength resolution is achieved using near-field exposure of photoresist through a cylindrical phase mask, allowing dynamic and high throughput continuous patterning. As an application, we present the fabrication of a transparent electrode in the form of a metallic wire grid by using the roller-based optical lithography method. To fabricate a mesh-type metal pattern, a specific phase-shift mask was designed and critical experimental parameters were also studied. As a result, a transparent conductor with suitable properties was achieved with a recently built cylindrical phase-shift lithography prototype designed to pattern on 100 mm2 of substrate area.

Simulation study of ‘perfect lenses’ for near-field optical nanolithography

Simulation results exploring the use of near field ‘perfect lenses’ (NFPLs) in optical nanolithography are presented. A 40 nm thick silver NFPL 20 nm beneath a chrome amplitude mask is studied using vector electromagnetic field modelling. For a 140 nm period grating mask illuminated at 341 nm, a sub-diffraction-limited image is obtained 23 nm below the NFPL. This opens up the possibility of proximity near field optical nanolithography. Resolution below 50 nm is predicted, which requires NFPL materials with very low loss. It is also found that the position of the image is a function of both mask period and the loss in the NFPL.

Near-field optical effects inside a photosensitive sample coupled with a SNOM tip

In this paper, we report a series of two-dimensional computerized simulations to gain more insight in the mechanisms responsible for near-field optical nanolithography (NFONL). Several significant factors are considered successively, e.g., the kind of tip used to illuminate the photosensitive sample (purely dielectric or coated tips), and the polarization of the incident electromagnetic field. A comparative study of the near fields generated by bulk dielectric and metallized tips is important to determine their relative capability as efficient tools for nanoindentation. In the same manner, the role of the tip–sample spacing during the exposure of the sample has also to be assessed to get a better control of the resulting nanoindentation patterns. Finally, a simultaneous study of both s- and p-polarizations is mandatory if we want to interpret recent experimental data issued from standard three-dimensional devices. With the help of these simulations, we explain some typical effects encountered during nanoindentation experiments realized with a reflection SNOM architecture.