Multilayer bottom antireflective coatings for high numerical aperture and modified illumination exposure systems

To achieve increasing resolution of optical lithography, exposure systems with a high numerical aperture (NA) are essential. The efficiency of the conventional single-layer bottom antireflective coating (BARC) structure will degrade as the incidence angle increases. This is because the reflectance at the resist/substrate interface increases in the large incident-angle regime. Here we demonstrate a multilayer BARC structure for high-NA and modified illumination exposure systems in ArF and F₂ lithographies. The multilayer antireflective structure is composed of conventional silicon oxynitride films. By adding an optimized structure, the reflectance can be maintained below 1% at a resist/high reflective substrate interface for the incident angles from 0 to 53 des (i.e. numerical aperture ∼0.8). The swing effect, in the resist is also shown to be significantly reduced.