5200 XP Overlay Measurement

Overlay metrology tools measure the positional relationship between patterned layers on a wafer. Overlay measurement is used to check whether a newly formed pattern is aligned correctly to features created in earlier process steps. Overlay tools belong to the metrology stage of semiconductor manufacturing and feed alignment and process control data back to lithography and related operations.

Overlay measurement systems inspect alignment targets on patterned wafers and calculate layer-to-layer registration error from the observed target positions. Overlay measurement systems generally use optical imaging and stage motion to visit selected measurement sites across the wafer. Overlay measurement systems typically report the resulting offsets for process control and matching of lithography performance.

Overlay metrology is used after patterning steps have created measurable alignment marks on the wafer. Overlay metrology commonly follows lithographic exposure and development, and it can also be used after etch or film steps when suitable targets remain readable. Overlay results are used to monitor registration performance through repeated patterning levels and to guide corrective action in process control.

Overlay measurement tools are applied in semiconductor processes that build multiple patterned layers whose relative placement must be controlled. Overlay measurement supports logic, memory, analog, power, and mixed-signal manufacturing wherever successive masks or reticles define interacting features. Overlay measurement is also used in process monitoring, tool matching, and verification of pattern transfer alignment across the wafer.