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Abstract

An in-situ spectrograph having a spectrometer module positioned at a reticle plane or at a wafer plane of a photolithography projection system is disclosed. The spectrometer module disperses light projected from an illumination source, and the produced spectrum may be recorded. The spectrum may be recorded using a photodetector or a layer of photoresist. The recorded spectrums produced by illumination sources of a plurality of steppers may be compared, thus providing a comparison of the wavelength characteristics, particularly the wavelength spread and intensity of the light of the illumination sources. A plurality of spectrometer modules may be used to provide a comparison of the central wavelength of light produced by the illumination sources. The absolute wavelength of light produced by an illumination source may be determined using a spectrometer module having a spectrometer grating.

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First Claim