Abstract: The investigation of x-ray mask fabrication distortions was initiated in an effort to identify the fabrication parameters responsible for the final x-ray mask shape and configuration. The investigation has identified the sources of fabrication-induced distortion in x-ray mask blank manufacture. The extraction of distortions at each process step allows for mask flatness control via distortion compensation as the mask fabrication process evolves. Interferometric characterization of the final mask blank configuration guarantees the mask flatness. Mask blanks with alignment windows are mapped to determine the locations of the alignment windows relative to the membrane. An additional interferometric wedge test is performed to determine the membrane tilt magnitude and orientation relative to the backside of the mask ring. With proper selection of mask blank materials and control of membrane material deposition and bonding parameters, x-ray masks up to 100 mm in diameter have been fabricated routinely with less than 5 $mu@m of bow. Fine-tuning of the x-ray mask configuration may be controlled by variations in the anodic bonding process parameters. Optimization of the anodic bonding process is currently in progress. !4
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