Large isolated Cr photomask defects (>=20 um) have become difficult to repair due to the fact that advanced repair tool capabilities are aimed almost exclusively at repairing very small defects at high magnification. Advanced focused ion beam (FIB) repair of large Cr defects is not only time-consuming, but in the end, only changes it into a transmission defect due to ion deposition (gallium staining). Current laser repair tools also have problems in that they generate a large amount of debris (splatter) due to the ablation mechanism being thermal. To avoid these problems and still repair the large chrome defect, we have developed a new method using a localized exposure technique to remove large isolated Cr defects. The mask was coated with optical resist and the defective area was exposed using white light. The mask was then sent through standard develop, wet Cr etch, and resist strip processes to remove the Cr spots. Initial results were very promising as the Cr spots were removed completely, and the repaired area showed no sign of glass damage. This repair technique has also been applied to both large and small Cr spots on MoSi phase-shift mask patterns. Future work will include aperture shape/size control and line edge repair will be investigated.
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