PHASE-CONTROLLED MODEL-BASED OVERLAY MEASUREMENT SYSTEM AND METHOD

摘要

PROBLEM TO BE SOLVED: To provide an overlay error measurement method for measuring overlay errors precisely, even when overlay targets are substantially smaller than those currently in use and are surrounded by other patterns.SOLUTION: An overlay measurement system 100 and method are disclosed that control a relative phase between a scattered component 116 and a specular component 114 of light to amplify weak optical signals before detection. The system and method utilize model-based regression image processing to determine overlay errors accurately even in the presence of inter-pattern interference.