Abstract
The impact of lens aberrations becomes severe when the critical dimensions (CDs) shrink.
The accurate measurement of both low- and high-order Zernike aberrations is important during a
photolithographic process. Based on the multi-illumination settings and principal component analysis
of aerial images, a novel <i>in situ</i> aberration measurement technique that can accurately measure all
the Zernike aberrations, except for the sinusoidal 2-θ and sinusoidal 4-θ terms (under
polar coordinates, and Z<sub>1</sub> to Z<sub>4</sub> are not considered) is proposed in this letter. The estimated
maximum error of the Zernike aberrations ranges from 0.43 to 0.78 mλ when the amplitudes of
the Zernike coefficients range from -20 to 20 mλ. The standard and root mean square errors are
both in the range from 0.14 to 0.4 mλ.
© 2012 Chinese Optics Letters
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