Method for reducing the resolution of an aerial image of a photolithography mask without reducing a signal-to-noise ratio and corresponding optical system

Abstract

The present invention relates to an optical system and method for reducing the resolution of an aerial image of a lithography mask (14) without reducing the signal-to-noise ratio. The method comprises: acquiring an aerial image of the lithography mask (14) using an optical system (10, 10'), wherein the structure of the lithography mask (14) is illuminated by a light source (12) and projected onto an image sensor (20) of a camera by a projection optics element (17) to generate an aerial image, wherein the pixel size of the image sensor (20) of the camera is smaller than the Nyquist limit defined by the resolution limit of the optical system (10, 10'); applying an anti-aliasing filter to the acquired aerial image; and downsampling the filtered aerial image to obtain an aerial image with reduced resolution. The invention relates to an optical system and a method for reducing the resolution of an aerial image of a photolithography mask (14) without reducing a signal-to-noise ratio, the method comprising: acquiring an aerial image of the photolithography mask (14) using an optical system (10’), in which structures of the photolithography mask (14) are illuminated by a light source (12) and projected onto an image sensor (20) of a camera by means of projection optics (17), thereby generating an aerial image, wherein a pixel size of the image sensor (20) of the camera is below a Nyquist limit defined by the resolution limit of the optical system (10’); applying an anti-aliasing filter to the acquired aerial image; and downsampling the filtered aerial image to obtain an aerial image of reduced resolution.

Images