Simulation of fine structures and defects in EUV etched multilayer masks

摘要

Rigorous electromagnetic scattering simulation is used to characterize mask diffraction for fine structures of various types of EUVL masks. The Cr/SiO_2 absorber mask, the etched multilayer mask and the new refilled multilayer mask are studied for lithography performance for line and space features for 32 nm node. The combined process window of 25 nm ISO line, 50 nm METAL1 line and 30 nm POLY line in a 90 nm pitch, are compared at σ of 0.6. The biased Cr/SiO_2 absorber masks have 182 nm DOF, while the biased etched binary mask has a higher DOF of 190 nm and the biased etched refilled binary mask has a DOF of 192 nm. The biased Cr/SiO_2 absorber masks show twice of CD variation and process window degradation due to variations in sidewall profiles than the etched and refilled multilayer binary masks. The void defect in the reflection region of multilayer structures can be repaired via deposition of transparent materials instead of absorbing materials when patterning the refilled multilayer masks. Simulations show that target CD and process window can be fully restored when the depth and width of repairing materials deposited for repair is optimized.