Lower Limit of Line Edge Roughness in High-Dose Exposure of Chemically Amplified Extreme Ultraviolet Resists

The line edge roughness (LER) of resist patterns is a critical issue in the high-volume production of semiconductor devices. LER is inversely proportional to the square root of exposure dose. However, LER cannot be reduced below a certain value when exposure dose is increased or when sensitivity is decreased.

In this study, the cause of this lower limit was investigated by Monte Carlo simulation. The dependences of the lower limit of LER on acid generator concentration, feature size, optical image contrast, and flare intensity were clarified. The decomposition effect of acid generators during exposure is a dominant factor for the lower limit of LER in the relationship between LER and exposure dose (or sensitivity).