Device for measuring overlay

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, comprising:

• 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;
• a second color filter configured to adjust a center wavelength and a band width of the other of the beams split by the first beam splitter so that the center wavelength and the band width of the other of the beams become suitable for acquiring an image of the second overlay mark;
• a beam combiner configured to combine the beams passed through the first color filter and the second color filter;
• an objective lens configured to condense the beam combined by the beam combiner at a measurement position on the wafer and collect the beam reflected from the measurement position;
• a second beam splitter configured to split the beam collected by the objective lens into two beams;
• a first detector configured to acquire an image of the first overlay mark by detecting one of the beams split by the second beam splitter;
• and
• a second detector configured to acquire an image of the second overlay mark by detecting the other of the beams split by the second beam splitter.