We have evaluated patterning accuracy during stage acceleration of EX-8D in which a beam deflection control system has been installed to compensate a beam positional shift depending on both the stage velocity and position. From the fact that there is no difference in patterning accuracy between stage acceleration phase and constant velocity phase, it was found that the control system functions accurately. We have also analyzed beam position deviation. The analysis results showed that improvement of the laser interferometer resolution, stabilization of the objection lens, and elimination of the ambient magnetic field change are necessary to achieve 1 Gbit class ultra-large-scale integrated patterning of 0.15 mu m within 10% beam position fluctuation. By adopting continuous writing during stage acceleration and deceleration while turning, the improvement of the throughput was also confirmed without reducing the patterning accuracy.