| 摘要 |
PURPOSE:To avoid an erroneous detection due to dirt, etc. by a method wherein, in a photoelectric detector for relative alignment device of two items such as mask and wafer in a semiconductor baking device, the photoreceiving surface of a photodetector is divided into two surfaces i.e. for detecting pattern and for receiving scattering light. CONSTITUTION:A photodetector 18 is composed of the photoreceiving surfaces 18a, 18b1-b4, 18c1-c4, 18d1-d4, 18e1-e4 respectively divided to receive signals independently. The central photoreceiving surface 18a receives the normal reflecting light of photoscanning beams. In such a constitution, it is recognized that photoscanning beams are scanning the detecting region while enabling synchroneous signals to be transmitted from a postprocessing circuit and reflecting power of a detected item to be measured. When a mark pattern 12a is detected, the sum of signals transmitted from the photoreceiving surfaces 18b1, 18c1, 18d1, 18b3, 18c3, 18d3, 18e3 will become the mark signals while the sum of signals transmitted from the photoreceiving surfaces 18b2, 18c2, 18d2, 18e2, 18b4, 18c4, 18d4, 18e4 will become the noise signals. When the mark signals and the noise signals are detected by said procedures, any noise signal synchronized with the amount almost similar to that of scattering light due to dirt, etc. contained in the mark signals may be detected easily. |
