Analysis and control of thermal and structural deformation of projection optics for 22-nm EUV lithography

Thirty-five to forty percent incident power will be absorbed by the multilayers of EUV optics which causes thermal deformation of mirrors, consequently affecting the optical performance of projection optics (PO). On the other hand the gravity and mounting of mirrors introduce the structural deformation of mirrors. So the thermal and structural deformations of mirrors are critical issues for extreme ultraviolet lithography (EUVL) at the technology node of 22 nm and below. In this paper, we employ several software packages to study and control the deformation of the PO which is employed in EUVL production tool with wafer throughput of one hundred 300 mm wafers per hour for the 22 nm technology. The results show that the deformation of PO is reduced effectively and the imaging performance of the PO is improved.