The Fundamentals of Overlay Metrology

摘要

Overlay metrology equipment historically has had little difficulty meeting state-of-the-art process error budgets through the 0.25 μm technology node. In fact, typical overlay measurement equipment performance has been better than metrology error budget allocations by 20-30%. This can be ascribed to several factors. First is the lavish error budget, compared with critical dimension (CD) metrology (3% of minimum design rule vs. < 1% for CD metrology).