Underlayer dependent local wafer deformation during EUV exposure

Abstract

In optical lithography process, a critical step involves projecting the optimal dose of energy onto the photoresist to fabricate the patterns of integrated circuits. These precise energy doses utilized for pattern projection across the wafer unavoidably induce local temperature increases, resulting in nano-level thermal deformation. The industry attempted to mitigate the effects of wafer heating by applying thermal actuators on the wafer chuck system. However, the criticality of wafer heating issue lies in the variation of thermal deformation across die and wafer, contingent upon the underlayer structures and materials employed. Even with equivalent dose, the gap of thermal deformation stemming from the underlayer configurations could contribute significantly to overlay budget constraints. Thermal deformation could constitute a large portion of the entire overlay budget when the same application is used for different underlayer structures without deformation correction.