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An effective repeating defect detection program is essential for a successful stepper-based photolithography process. Repeating defects caused by problems with the reticle or stepper optics have a direct and dramatic impact on wafer yield. As die sizes increase and the number of die per field decrease, the importance of this inspection program increases to a critical level in manufacturing. To protect against yield-impacting repeating defects, a variety of automated inspection strategies have been implemented in lithography processes, including particle inspection of the reticle, metal on glass wafer inspection, and single layer resist on silicon inspection. Each of these techniques have limitations in the manufacturing area. A new technology, resist on quartz inspection, has recently emerged for the detection of repeating defects in high volume wafer fabrication. Production reticles are stepped onto resist-coated, transparent quartz wafers. After development, a repeating defect inspection can be automatically performed using transmitted light which provides optimum defect detection sensitivity and throughput. This novel technique uses standard wafer fabrication processes to produce the resist images. This paper discusses the implementation of resist on quartz inspection in a manufacturing environment. Focus/exposure matrices were run to determine the process window for generating resist images on quartz substrates and to confirm inspection performance on typical production resist images. The resist on quartz inspection strategy implemented in the production area is explained. Examples of repeating defects detected by the inspection program are shown. To confirm the capability of processing quartz wafers with an existing production lithography process, a 5X VeriMaskTm 1045 test reticle was used to generate resist images. The reticle has programmed defects of varying sizes, types and locations on one micron geometries. Test images were created with various exposure and focus conditions, and the programmed defects measured using a low voltage SEM. The resist images were inspected on a KLA-259 Resist Image Inspection System. Capture rate curves generated from the inspection and measurement data are shown.
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