Multiple wavelength linear zone plate alignment apparatus and method
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United States of America Patent
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Nov 3, 1987
Grant Date -
N/A
app pub date -
Mar 6, 1986
filing date -
Mar 6, 1986
priority date (Note) -
Expired
status (Latency Note)
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Abstract
An optical alignment apparatus and method for a semiconductor lithography mask and wafer utilizes two monochromatic light sources of different wavelengths. The mask contains targets in the form of linear Fresnel zone plates and the wafer contains a reflecting grating. Incident illumination from the two light sources illuminates the mask targets and is reflected from the wafer gratings in various intensity depending on the physical characteristics of the wafer and mask layers and thicknesses and by the targets. A detector detects the strongest of the diffracted return beams from each of the monochromatic light sources and uses the strongest to align the targets and grating on the mask and wafer for more accurate printing of mask patterns on the wafer.
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