JPS5646533A - Detection of mark position for exposing electron beam - Google Patents

Abstract

PURPOSE:To accurately match an electron beam with a material to be exposed by reciprocatingly scanning the electron beam across a mark over its width at a distance L, measuring the distances A, B and C, D from the starting and the turning points of scanning to both ends of the mark and calculating the position of the mark. CONSTITUTION:The electron beam is reciprocatingly scanned by a scanner 4 from a computer 5 between the points P and Q across the mark M1 on the material. The variation of the reflected electrons is detected by the detector 8 at the end of the mark, is amplified by an amplifier 9, a negative signal is then inverted, and is differentiated by a differentiator 10. When the differentiated signal is at zero level, a pulse is produced, the counting of the pulses 11 by a counter 12 is stopped as produced upon starting scanning from the point P, a counter 13 is stopped by the second pulse, and the counted values A, B are applied to the computer 5. When the mark is scanned to the point Q, the counted values are cleared, counting is again started, and the counted values C, D are similarly obtained. Thus, the distance R between the point P to the center of the marks can be obtained by R=[A+B+(L-C)+(L-D)]/4. The same operation is conducted in Y direction. In this manner, the position of the mark can be accurately detected, and an accurate position matching can be consequently conducted.