Abstract: Aberrations are determined from wafers exposed using atest reticle having blazed gratings with orientationsfrom 0 to 337.5 degrees in increments of 22.5 degrees.The image of the phase grating is micro steppedthorough focus on the surface of high absorptionphotoresist. A second blanket exposure is applied tothe latent images to make the developed resist imageshave a surface relief linearly related to the aerialimage intensity. The first order diffraction efficiencyof this surface grating is directly propagational tothe first harmonic of the surface relief. Thisdiffraction efficiency is recorded as a digitized dark-field image and processed to evalute the aberrations.These images are simulated and matched to thoserecorded in the photoresist by adjusting theaberrations to achieve a best match. The primaryazimuthal aberration contributions are separated byFourier analysis into coma, astigmatism, 3 leaf clover,etc. and laser used to indicate lens quality. Severalgrating frequencies are required to separate higherorder components of each azimuthal aberration. Only onegrating frequency is used in the data reported here andall orders of each azimuthal aberration are lumped intoequivalent primary azimuthal aberrations. !5
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