SUBMICROMETER DEFECT DETECTION IN PERIODIC STRUCTURES BY PHOTOREFRACTIVE HOLOGRAPHY - SYSTEM-DESIGN AND PERFORMANCE

We have built an adaptive system capable of detecting submicrometer de fects in periodic structures by using real-time holography in photoref ractive crystals. We summarize the design and optimization of the defe ct-enhancement system. We present representative results of 0.2- to 0. 5-mum diameter defect detection on two different periodic substrates: chrome-on-glass masks and patterned silicon wafers. On patterned silic on we detect 94% of the 0.5-mum diameter defects with three false posi tives, while inspecting an area greater than 1 mm2 in 20 s or less. Th e throughput on the glass masks is somewhat less. To the best of our k nowledge, these defects have an area 100 times smaller than those prev iously detected with any real-time holographic technique.