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Focused ion beam systems for mask repair have been built by several companies. These systems differ from each other in beam optics design (one or two lens systems) and various mechanical and electrical aspects, but all use the same Gallium ion beam from an "elemental" ion source to effect repairs at the mask surface. The disadvantage of this approach is an inherent inability to select an ion beam optimized for each task required in mask repair and the problems associated with "gallium staining" of the mask substrate. We report on an advanced focused ion beam mask repair system under development that combines a mass separator with two lenses in the ion optics. Significant advantages result from this design when used with "alloy" vs "elemental" liquid metal ion sources. For each task, the mass analyser selects the most suitable ion species from the beam emitted by the source. A beam of ions having a low sputter rate is used during imaging and critical dimension measurements, minimizing damage to the mask and eliminating "gallium staining". During repair, a beam of ions selected for the task being performed is used to optimize the defect repair process. The ion beam spot size in the NanoFix is changeable in size from 100 nanometers to 500 nanometers, with the beam voltage being variable from 4 kV to 60 kV. The x-y stage has travel for the repair of seven inch mask plates. The target and optical chambers are differentially pumped with high speed vacuum pumps allowing ion-beam-assisted chemical vapor deposition in the target chamber while maintaining a low pressure in the optical chamber. The design, performance, and additional advantages of the NanoFix in mask repair applications are described for a simple to use and reliable machine for the production environment.
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