Inspection apparatus to detect a target located within a pattern for lithography

摘要

The invention relates to detecting targets located within patterns. The invention operates in the pupil plane by filtering the fourier transform from the surrounding pattern. In particular the method includes performing a fourier transform on reflected radiation data to form fourier transform data; removing portions of the fourier transform data which correspond to the target to form reduced fourier transform data; interpolating the portions of the reduced fourier transform data which were removed, to form product fourier transform data; and subtracting the product fourier transform data from the fourier transform data.

主权项

1. A method of measuring a target on a substrate, wherein the target is located within a surrounding pattern on the substrate, the method comprising:
illuminating the target and the surrounding pattern with radiation; detecting the radiation reflected by the target and the surrounding pattern and forming a set of Fourier transform data based on the detected radiation; removing portions of the Fourier transform data which correspond to the target to form reduced Fourier transform data; interpolating the reduced Fourier transform data over the removed portions to form product Fourier transform data; and subtracting the product Fourier transform data from the Fourier transform data to form target data.