Standalone alignment technology enabling feed-forward compensation of on-product overlay errors

A standalone alignment technology was developed as a fundamental solution to improve on-product overlay (OPO). It enables high performance alignment measurements, and delivers state-of-the-art feed-forward corrections to exposure scanners. Dense alignment sampling and high order alignment correction is effective for scanner fingerprint matching and for correcting heavy distortion at a wafer edge. A mark asymmetry correction is detailed as effective solution which improves the OPO performance for heavily processed wafers. An OPO test result showed significant improvement using its feed-forward corrections. A high accuracy topography sensor is described as a new metrology innovation. The standalone alignment technology provides critical metrology tool functions such as process monitoring as well.