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.