A BEAM DRIFT REDUCTION DEVICE FOR THE X-RAY MASK E-BEAM WRITER, EB-X2

A new drift reduction device for the X-ray mask e-beam writer, EB-X2, has been designed to keep reflected electrons (REs) and secondary elec trons (SEs), which can charge the inner surface of the column, from re -entering the column. First, two electrodes, which have a circular ope ning in the center through which the incident beam passes, are placed between the column and the specimen. They keep REs re-entering the col umn. Second, a voltage of -50 V is applied between the two electrodes to prevent SEs from re-entering the column. Electron trajectory calcul ations revealed that the device keeps 84% of REs and 100% of SEs from re-entering the column. The effects of this device on the EB-X2's elec tron optical characteristics that is, beam shape distortion, deflectio n distortion, and beam shift caused by electric-field leakage from the electrodes-were also estimated numerically. The calculated results sh ow that the device can reduce beam drift without degrading the pattern ing accuracy.