Abstract: An overlay measurement device measures an error between a first overlay mark and a second overlay mark respectively formed on different layers formed on a wafer. The device is configured to detect a height of the first overlay mark based on a change in the signal of the first detector according to a change in the relative position of the objective lens with respect to the wafer in the optical axis direction and detect a height of the second overlay mark based on a change in the signal of the second detector according to a change in the relative position of the objective lens with respect to the wafer in the optical axis direction.

Abstract: An overlay measurement device for measuring an error between a first overlay mark and a second overlay mark respectively formed on different layers formed on a wafer is proposed. The device includes a light source, a first beam splitter configured to split a beam emitted from the light source into two beams, a first color filter configured to adjust a center wavelength and a band width of one of the beams split by the first beam splitter so that the center wavelength and the band width of one of the beams become suitable for acquiring an image of the first overlay mark.