Alignment method and apparatus using previous layer calculation data to solve critical alignment problems

摘要

An method and apparatus for aligning a mask to a wafer for photolithographic processing steps which does not use optical alignment. Each wafer is provided a unique identification code, such as a bar code. As wafers are processed through photolithographic steps where optical detection of an alignment mark can be easily accomplished the alignment data for each wafer is stored in a memory unit. At the next photolithographic step a detector reads the identification code and identifies the wafer being processed. The wafer identification is fed to a data processing unit which retrieves the alignment data for that wafer fro the memory unit. The data processing unit then feed alignment data to a mechanical controller which positions the wafer relative to the mask image being used in the photolithographic step.