Study of heating effect on CAR in electron beam mask writing

Abstract

Heating effect was evaluated for EBM-6000 which is operated at high current density of 70A/cm² and acceleration voltage of 50kV. FEP171 as widely used for current productions and lower sensitivity resists are tested. Lower sensitivity resist is one of key items to achieve highly accurate Local critical dimension uniformity (LCDU) because of shot noise reduction. CD variations in experiment are compared with simulated temperature changes induced by heating effect. Then, the ratio, ΔCD/ΔT, is found mostly constant for every resist, 0.1 nm/C°. Writing conditions are estimated to meet CDU spec of hp45 generation for a worst case pattern, i.e. 100% density pattern. For FEP171, the maximum shot size of 0.85 μm shot size at 2pass writing mode is sufficient. It should be reduced to 0.5 μm at 2pass writing mode for every lower sensitivity resist. When 4pass writing mode is used, the maximum shot size of 0.85 μm is available. Writing conditions and writing time for realistic patterns are also discussed.