Marks and method for multi-layer alignment

摘要

Marks and a method for multi-layer alignment. A first layer with first alignment marks is formed on a semiconductor substrate, wherein the first alignment marks are separated parallelly by a predetermined distance. A second layer with second alignment marks is formed on the first layer, wherein the second alignment marks are separated parallelly by a predetermined distance. The shift distance of each first alignment mark is measured to calculate a first midpoint between the first alignments. The shift distance of each second alignment mark is measured to calculate a second midpoint between the second alignments. A third midpoint acting as a datum point between the fist midpoint and the second midpoint is calculated.