Mask bias requirement for 0.13 mu m e-beam block exposure lithography

Coulomb interactions have been discussed as an obstacle for 0.13 mu m line and space (L/S) resolutions in the block exposure or the cell projection li thography. In this article, effects of the Coulomb interactions are experim entally analyzed in the 50 kV block exposure lithography system. Blurs of t he e-beam profiles, which characterize the Coulomb interactions, were obtai ned by knife-edge experiments. From the results, the following theoreticall y predicted facts have been clarified. The blur increases with the increasi ng current monotonously. We have obtained Linear relationships, delta=0.03x I(b)+0.05(mu m) between the blurs and an a-beam current. The dynamic refocu sing technique can suppress the Coulomb interactions only partially. In ord er to resolve 0.13 mu m L/S, practical methods to reduce the Coulomb intera ctions by reducing the current are needed. It is clarified that mask biasin g, where widths of the mask openings are narrowed, is more effective to ach ieve high contrast than current density reduction or shot size reduction. I t is also clarified that the mask biasing is effective to resolve 0.13 and 0.10 mu m L/S patterns. We have applied the current reduction techniques an d have successfully obtained fine 0.13, 0.12 and 0.10 mu m L/S patterns. (C ) 1998 American Vacuum Society. [S0734-211X(98)04906-3].