Patent ID: 8520189
Filing Date: 2013-08-27
Classification: G02B,G03F

Abstract:
1. A method comprising: directing a beam of radiation, with optics of a lithography tool, along an optical axis toward a workpiece support; determining a longitudinal aberration imparted to the beam by the optics along the optical axis of the lithography tool; measuring a spectrum of the beam at a first time to obtain a first spectral profile; measuring the spectrum of the beam at a second time subsequent to the first time to obtain a second spectral profile; determining a first intensity center of the first spectral profile, determining a second intensity center of the second spectral profile, and determining a spectral offset between the intensity centers; calculating an adjustment amount by multiplying the spectral offset by the longitudinal aberration; and adjusting a position of the workpiece support along the optical axis by the adjustment amount.