Shot noise effect on LER and throughput in LEEPL system - art. no. 65172J

LEEPL (Low Energy Electron-Beam Proximity Projection Lithography) uses low energy of electrons of 2 KV. In such a low energy, electrons behaves quite differently in the resist to higher energy electrons even such as in 10 KV. Under these conditions the statistical variations of electrons known as shot noise and its effect to LER is known to be much smaller than a simple consideration of shot noise variation due to the primary electrons alone. In order to estimate how much smaller the effective LER in LEEPL, we introduce a reduction factor: f which is the ratio of the shot noise component of the observed LER against the shot noise factor due to the statistical variation of primary electrons alone. The value of f was estimated as 0.38 from two independent methods, namely one of from experimental result and other from the computer simulation. Furthermore the analysis is extended to taking account of the effect of the acid diffusion in the case of CAR resist. Then the value of f is further reduced to 0.25. Finally, as consequence of this analysis, we obtain the throughput of LEEPL tool as approximately 80, 60, 40 W/Hr for 65, 45, 32 nm device nodes respectively. As conclusion, CoO of LEEPL is several times smaller than that of ArF Immersion and EUV systems.