Surface profile measuring apparatus and method

A surface profile measuring apparatus comprising:

• a light source operable to emit a light beam having a plurality of wavelengths;
• a splitter unit operable to split the light beam into a reference beam and a measuring beam;
• a first diffraction grating operable to diffract the reference beam;
• a second diffraction grating operable to diffract the reference beam diffracted by the first diffraction grating and cause the diffracted reference beam to be incident on the first diffraction grating again;
• a detection unit operable to receive an interference beam in which the reference beam, which is incident again on the first diffraction grating and diffracted again by the first diffraction grating, and the measuring beam, which is reflected by a sample surface, optically interfere with each other, and operable to detect an interference intensity signal for each wavelength in the interference beam;
• a plurality of parallel grating grooves provided in a surface of the second diffraction grating;
• a shifting unit operable to shift the second diffraction grating in a direction perpendicular to the plurality of parallel grating grooves in the second diffaction grating surface;
• a calculation unit operable to calculate a phase of the interference intensity signal for each wavelength in the interference beam on a basis of the interference intensity signal for each wavelength varying with a degree of shift of the second diffraction grating caused by the shifting unit;
• and
• a measurement unit operable to measure the sample surface on a basis of the phase of the interference intensity signal for each wavelength.

A surface profile measuring method comprising:

• emitting a light beam having a plurality of wavelengths;
• splitting the light beam into a reference beam to enter a first diffraction grating and a measuring beam to enter a sample surface, wherein a plurality of parallel grating grooves are provided in a surface of the first diffraction grating;
• reflecting the reference beam diffracted by the first diffraction grating and causing the reflected reference beam to be diffracted again by the first diffraction grating;
• detecting an interference intensity signal for each wavelength in an interference beam through the use of a detection unit by receiving the interference beam in which the reference beam diffracted again by the first diffraction grating and the measuring beam reflected by the sample surface optically interfere with each other;
• shifting the first diffraction grating in a direction perpendicular to the plurality of parallel grating grooves in the first diffraction grating surface;
• calculating a phase of the interference intensity signal for each wavelength in the interference beam on a basis of the interference intensity signal for each wavelength varying with a degree of shift of the first diffraction grating performed by the shifting;
• and
• measuring the sample surface on a basis of the phase of the interference intensity signal for each wavelength.