In situ aberration measurement technique based on multi-illumina...

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 in situ aberration measurement technique that can accurately measure all the Zernike aberrations, except for the sinusoidal 2-\theta and sinusoidal 4-\theta terms (under polar coordinates,