PURPOSE: To achieve a quick position measurement by providing a reference reflection surface obliquely to a surface crossing the traveling direction and then constituting a detector with an area sensor.
CONSTITUTION: Radiation beams from a white color light source 21 are split into two fluxes of light by a beam splitter 23 and one flux of light 24 is applied to a mask M and a wafer W and the other flux of light 25 is applied to a reference reflection surface 27 of a reflection mirror 26 which can travel freely in Y-axis direction. The fluxes of reflection light of the mask M and wafer W and the flux of reflection light of the reflection surface 27 are matched by the splitter 23 and the flux of light is detected by a detector 28. Then, based on the position of the reflection surface 27 and the interference position of the detector 28 when both reflection lights interfere with each other, the position of a sample surface is measured. In this case, the reflection surface 27 is formed on the surface which is inclined by an angle of θ to the surface crossing the Y axis which is the traveling direction and the angle θ is set to an angle where the reflection light passes the same inverse path as the incidence path. Also, the detector 28 is constituted by, for example, a CCD area sensor, thus simultaneously measuring the spacing length between a mask and a wafer without traveling on the reflection surface 27.
ISHIBASHI YORIYUKI
TOUKI TATSUHIKO
NAGAHAMA HIROYUKI
TOPCON CORP