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The work reviewed will describe a particular effort in the area of overlay matching based on the BaseLiner™ package marketed by ASML. BaseLiner relies on the concept of Scanner Baseline Constants (SBCs). Traditionally, optical lithography systems are controlled by many numerical parameters known as Machine Constants (MCs). MCs are typically generated by a lithography system during in situ or other system based tests that generate and optimize the MCs for a very specific test condition set. The concept of SBCs introduces a “middle layer” of offsets that forces tools to be closely matched to one another under general lithography conditions, not just the specific test conditions used for MC generation. The methodology is designed to handle specific product layouts.