Abstract: A method of irradiating to pattern a photosensitive layer such as a resist (L2) immersed in a fluid (L3), involves applying a removable transparent layer (L4, L5), projecting the radiation onto the resist through the immersion fluid and through the transparent layer, such that imperfections in the fluid are out of focus as projected on the surface, and subsequently removing the transparent layer. The transparent layer can help distance such imperfections from the focus of the radiation on the surface and so can reduce or eliminate shadowing. Hence the irradiation can be more complete, and defects reduced. It can be particularly effective for imperfections in the form of small bubbles or particles in the immersion fluid especially at the fluid/surface interface for example. The radiation can be for any purpose including inspection, processing, patterning and so on. The removal of the transparent layer can be combined with a step of developing the resist layer.

Abstract: The minimal feature width (CD) of a pattern of device features configured in a substrate layer by means of a lithographic process can be reduced considerably, without reducing process latitudes (DOF), by substantially extending the post-exposure bake step and reducing the exposure dose. By the same measures the isofocal CD can be tuned to the design CD so that for an arbitrary CD process latitudes are enlarged.