- Central Research Laboratory, Hitachi Ltd., Kokubunji Tokyo 185, Japan
- Instruments Division, Hitachi Ltd., Katsuta Ibaraki 312, Japan
A new mark detection method has been developed using the symmetry of mark signals. The calculation of the symmetry is executed by a digital signal processor in order to reduce the detection time to less than 100 msec. Detection accuracy is estimated by a simulator. Calculated accuracy is compared with experiment results. The detection system is adopted in a new electron beam lithography system(1).