Deflector and correction coil calibrations in an electron beam block exposure system

Abstract

Mask deflectors and correction coils in an electron beam block exposure system are calibrated to expose 48 mask patterns in a deflection area with the same current density and at the same position on a wafer. The calibration has six measurement steps. When a mask stage changes area positions on a mask, only the last step needs to be executed during exposure. This last step takes about 2 s for measurement. Calibration results show that the current density through each mask pattern differs less than 1.6% from the mean value. Exposed position errors on a wafer are below 0.04 μm for 48 mask patterns. These position errors are corrected by additional deflections with an electrostatic minor deflector. To improve stitching accuracies between exposed patterns, we discuss another routine to adjust beam sizes and rotations of spots on a wafer.