| 摘要 |
PURPOSE:To enable the maintenance of a space between a wafer and a mask at a fixed value in any process by a construction wherein a rotary and non-symmetrical means of altering a luminous flux width is provided in optical paths through which luminous fluxes from two substances spaced from each other reach an interference fringe forming means. CONSTITUTION:A space between a central peak Fc and a side peak Fs detected by a photodetector 30 such as a photodiode is compared with a reference value in a signal processing circuit 36, and based on the result of this comparison, an actuator control circuit 37 drives actuator rods 35, 35' and 35'' vertically. Transferring the relative positions of a mask and a measuring optical system, or measuring a space between a plurality of points, the result of the measurement and a reference value are compared with each other in a signal processing circuit 30. Based on the result of this comparison, the rods 35, 35' and 35'' are controlled vertically through the intermediary of the actuator control circuit 37, and thereby a space between a mask and a wafer can be controlled at a value tobe prescribed. |
