Method and Apparatus For Maintaining Depth of Focus

摘要

A method includes directing a beam of radiation along an optical axis toward a workpiece support, measuring a spectrum of the beam at a first time to obtain a first profile, measuring the spectrum of the beam at a second time to obtain a second profile, determining a spectral difference between the two profiles, and adjusting a position of the workpiece support along the optical axis based on the difference. A different aspect involves an apparatus having a workpiece support, beam directing structure that directs a beam of radiation along an optical axis toward the workpiece support, spectrum measuring structure that measures a spectrum of the beam at first and second times to obtain respective first and second profiles, processing structure that determines a difference between the two profiles, and support adjusting structure that adjusts a position of the workpiece support along the optical axis based on the difference.

主权项

1. A method comprising:
aligning a first exposure field along an optical axis, the first exposure field being supported by a workpiece support; directing a first beam of radiation, with optics of a lithography tool, along the optical axis toward the first exposure field, the optics of the lithography tool having a longitudinal aberration; measuring a spectrum of the first beam to obtain a first spectral profile; aligning a second exposure field along the optical axis, the second exposure field being supported by the workpiece support; directing a second beam of radiation, with optics of the lithography tool, along the optical axis toward the second exposure field; measuring the spectrum of the second beam to obtain a second spectral profile; calculating a spectral offset between the first and second spectral profiles; calculating an adjustment amount based on the spectral offset and the longitudinal aberration; and adjusting a position of the workpiece support along the optical axis by the adjustment amount.