A method of forming a dielectric stack on a pre-treated surface. The hole in the boat hull may be tapered prior to bonding. The filter transmits radiation at a wavelength of 157 nm for exposing an image of a mask pattern on a resist-coated substrate whilst attenuating radiation resulting from fluorescence in optical components of the lithographic projection apparatus, caused by the imaging radiation, and which if not attenuated would reduce the contrast of the image exposed in the resist. The second top edge has a point closest to a geometric center of the first bottom.