Determining maximum positional errors of structures on wafers employs virtual wafer and wafer parameter model to differentiate between rejection and rework

摘要

Positional errors on wafers of a batch are determined. They are transferred onto the same positions of a virtual wafer (8). Parameter- and probability distributions of the error positions are determined using a wafer parameter model (WPM), with which the positional error is described as a function of position on the wafer. An optimization algorithm, using positional errors and their allocation to the respective wafer positions, aims for minimum residual error. Systematic and random distribution errors are separated in accordance with algorithms expressed as a series of equations. Results are taken to give the maximum positional errors and the parameter distributions of the entire batch. They are further employed for classification into batches of wafers: not to be corrected, correctable, and incapable of correction. Correctable wafers are re-worked.