Importance

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Abstract

In a method for the projection printing of masks onto a wafer coated with a photosensitive layer, said mask and said wafer being aligned by imaging alignment patterns of said mask onto said wafer by means of alignment light. In order to obtain a high-intensity and high-contrast alignment signal generated by plotting said alignment light reflected from said wafer, said alignment light comprises at least two narrow wavelength ranges spaced from each other on the wave length scale, in said ranges said photosensitive layer of said workpiece being non-sensitive or low-sensitive, determining the intensity of said alignment light reflected from said workpiece and generating an alignment signal from the wavelength range of said alignment light having highest intensity.

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First Claim