Patent ID: 10416569

Abstract:
An attenuation filter is configured to define attenuation of the intensity of ultraviolet radiation with a specified working wavelength from a wavelength range of 150-370 nm according to a specifiable local distribution in a projection lens of a microlithographic projection exposure apparatus. The attenuation filter has a substrate and an absorption layer on the substrate. The substrate is sufficiently transparent at the working wavelength. The absorption absorbs incident ultraviolet radiation of the working wavelength according to the specifiable local distribution at different locations of a used area to varying degrees. The attenuation filter reduces or avoids a thermally induced wavefront variation error in the ultraviolet radiation which has passed through the attenuation filter owing to locally varying heating of the substrate, which is caused by the absorption of the ultraviolet radiation that varies locally over the substrate. A thickness of the substrate is less than 100 μm.