| 摘要 |
PURPOSE: To accurately determine a focal point and to quantitatively measure the size and direction of a deviation in a focal point by a method wherein light is changed in phase by an angle of certain degrees other than 180 deg. to light which passes through a substrate, and a phase-changed pattern is optically projected onto the surface of an object through a projection-type image formation system. CONSTITUTION: A projection image forming system 10 is equipped with a light source device 12 composed of a mirror 14, a mercury arc lamp 16, a light filter 18, and a condensing lens system 20. The light source device 12 irradiates a mask structure 22 with light. Light passing through the mask structure 22 intersects a reduction lens 24, and the reduction lens 24 aligns the focal point of a mask pattern with a specific lens field formed on a semiconductor wafer 28. When the phase change angle of a phase changing matter 44 is other than 180 deg. and the focal point is incomplete, a measurable deviation in the focal point is represented on a projected test pattern, so that phase changing matters are alternately used. By this setup, focal point errors are lessened, and a focal point can be accurately measured. |
