Position Calibration of Alignment Heads in a Multi-Head Alignment System

摘要

A calibration method is disclosed, for the position calibration of secondary alignment heads with a primary alignment head in a multi-head alignment system, such as that used for the measurement of markers on the surface of a wafer, as carried out during a lithographic process in the formation of circuits in or on the wafer. A plurality of offset measurements are made for at least one of the secondary alignment heads, so that the offset of the secondary alignment heads with respect to the primary alignment head can be measured, and used as correction data in subsequent wafer measurement calculations.