Study of μDBO overlay target size reduction for application broadening

With these proceedings we present mu-diffraction-based overlay (mu DBO) targets that are well below the currently supported minimum size of 10 x 10 mu m(2). We have been capable of measuring overlay targets as small as 4 x 4 mu m(2) with our latest generation YieldStar system. Furthermore we find an excellent precision (TMU < 0.33 nm for 6 x 6 mu m(2)) without any compromise on throughput (MAM time < 30 ms). At last a study that compares four generations of YieldStar systems show clearly that the latest generation YieldStar systems is much better capable of reading small overlay targets such that the performance of a 16 x 16 mu m(2) on an early generation YieldStar 2nd-gen is comparable to that of a 8 x 8 mu m(2) on the latest YieldStar 5th-gen. This work enables a smaller metrology footprint, more placement flexibility and in-die overlay metrology solutions.