Method and system for increasing alignment target contrast

摘要

A semiconductor wafer is aligned using a double patterning process. A first resist layer having a first optical characteristic is deposited and foams at least one alignment mark. The first resist layer is developed. A second resist layer having a second optical characteristic is deposited over the first resist layer. The combination of first and second resist layers and alignment mark has a characteristic such that radiation of a pre-determined wavelength incident on the alignment mark produces a first or higher order diffraction as a function of the first and second optical characteristics.