Electron Optics of Electron Beam Lithography System with Multi-Micro Columns

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Electron beam lithography with multi-micro columns is a quite promising method in the next node of lithography when the minimum line width becomes less than 50 nm. EB lithography has a great advantage that we can directly expose the wafers without masks. I investigated the key factors when multi-micro columns are arranged in a row or like a grid. The electric field in columns is numerically calculated with the surface charge method which can be applied in 3D space.Individual column has to control independently in maskless operation, but the neighboring columns do not permit with any coupling. Beam turn-on and turn-off is basic control in multi-micro system and there are two usual methods for ON/OFF operation: beam cut-off by the gate voltage of electron guns and beam blanking out by a deflector and an aperture. After the 3D-field analysis and the trajectory simulation, it is found that the beam blanking method is much advantageous because weak influence in the adjacent column. It is caused that deflector has a dipole field and this field decrease much sharp than Coulomb potential field. The trajectory shift by the leakage field is calculated in a few models quantitatively and the ability and the prospect of multi-micro column lithography system are discussed.