Wavelength-tunable fiber optic light source and overlay measurement device with same

An overlay measurement device for measuring an interlayer overlay error of a sample on which overlay marks, which include a first overlay mark and a second overlay mark respectively formed on different layers, are formed, the overlay measurement device comprising:

• an illumination optical system configured to illuminate the overlay marks on the sample;
• a main beam splitter configured to split light reflecting off the overlay marks into a first beam and a second beam;
• a first detector configured to receive the first beam and generate a first overlay mark image in which the first overlay mark is in focus;
• a second detector configured to receive the second beam and generate a second overlay mark image in which the second overlay mark is in focus;
• a first imaging optical system configured to image the first beam on the first detector;
• and
• a second imaging optical system configured to image the second beam on the second detector,
• wherein the illumination optical system comprises the wavelength-tunable fiber optic light source, and
• wherein the wavelength-tunable fiber optic light source comprises:
• a broadband light source configured to emit light;
• a light source housing including an interior space to accommodate the broadband light source, a first window through which light emitted from the broadband light passes to form a first illumination, and a second window through which light emitted from the broadband light source passes to form a second illumination;
• a first variable filter placed in an optical path of the first illumination that has passed through the first window, and configured to adjust a wavelength band of the first illumination;
• a second variable filter placed in an optical path of the second illumination that has passed through the second window, and configured to adjust a wavelength band of the second illumination;
• and
• a fiber combiner including a first input port and a second input port through which the first illumination that has passed through the first variable filter and the second illumination that has passed through the second variable filter are input, respectively;
• and an output port through which a combination of the first illumination and the second illumination is output.