| 摘要 |
PURPOSE:To always realize draft with optimum amount of irradiation and high accuracy of pattern dimension by controlling automatically the amount of irradiation of electron beam in accordance with difference of pattern density. CONSTITUTION:When a circuit pattern data of photo mask 5 enters a control computer 6 from a MT reader 8 and is then input to an irradiation amount control circuit 12, a pattern density calculating circuit 13 immediately calculates the pattern density of photo mask and also calcultes a ratio. Thereby, an electron amount control circuit 14 sets a coefficient data corresponding to such ratio, an emission current of electron gun 2 and a driver circuit of electron optical lens 3 are controlled on the basis of such setting value and thereby amount of electron irradiated to photo mask 5 is controlled. Namely, amount of irradiation increases when the area ratio is high but decreases when the ratio is low. Simultaneously, the photo mask 5 is irradiated with electron beam in the specified pattern for drafting by controlling the electron beam blanking electrode 4 with pattern information stored in the design data storing memory 11. |
