In this paper, we propose a method named as AMAI-PCA to extract aberration levels using aerial image measurements
and present its experimental results on lithographic tools. Based on physical simulation and statistical analysis, a linear
regression matrix is obtained establishing a connection between principal component coefficients of specific aerial
images and Zernike coefficients. In the application phase, the aberrations of the projection lens are solved via the use of
this regression matrix. An engineering model is established based on an extension of theoretical model that incorporates
all the significant systematic errors. The performance of the engineering model applied on a 0.75 NA ArF scanner is
reported. In the experiment, measurement marks oriented in orthogonal directions are used and aerial images on 9 field
points are measured. To verify the repeatability of this technique, every point is measured 20 times. By inputting the
aerial images into the engineering model, Zernike coefficients are solved and the results are analyzed. The wafer
exposures were performed to evaluate the results of aberration correction.
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