Optical measurement apparatus and optical measurement method
An optical measurement apparatus includes an irradiation optical system which linearly irradiates a measurement target with measurement light having a certain wavelength range, a measurement optical system which receives linear measurement interference light which is transmitted light or reflected light originating from the measurement target as a result of irradiation with the measurement light, and a processing device. The processing device includes a first calculation module that calculates a modification factor depending on with an angle of incidence on the measurement optical system from each measurement point in association with a region in the two-dimensional image corresponding to each measurement point in the measurement target irradiated with the measurement light and a second calculation module that calculates optical characteristics of the measurement target by applying the corresponding modification factor to a value for each pixel included in the two-dimensional image.
1. An optical measurement apparatus comprising:
an irradiation optical system configured to linearly irradiate a measurement target with measurement light having a certain wavelength range;
a measurement optical system which receives linear measurement interference light which is transmitted light or reflected light originating from the measurement target as a result of irradiation with the measurement light; and
a processing device, wherein
the measurement optical system comprises
a diffraction grating which expands the measurement interference light in a wavelength direction orthogonal to a longitudinal direction of the measurement interference light, and
an imaging portion which outputs a two-dimensional image by receiving the measurement interference light expanded in the wavelength direction by the diffraction grating, and
the processing device comprises
a first calculation module that calculates a modification factor depending on an angle of incidence on the measurement optical system from each measurement point in association with a region in the two-dimensional image corresponding to each measurement point in the measurement target irradiated with the measurement light, and
a second calculation module that calculates optical characteristics of the measurement target by applying a corresponding modification factor to each pixel value included in the two-dimensional image.
2. The optical measurement apparatus according to claim 1 , wherein
the modification factor includes a wave number representing a parameter including a wavelength of the measurement light and a refractive index of the measurement target, and
the wave number is calculated in consideration of magnitude of a corresponding angle of incidence, for each pixel position in the two-dimensional image.
3. The optical measurement apparatus according to claim 2 , wherein
the second calculation module is configured to
subject a row of values resulting from conversion in accordance with a relational expression for linearizing the pixel value in the two-dimensional image corresponding to a measurement point of interest with respect to a phase factor, to Fourier transform with respect to a row of corresponding wave numbers,
determine a film thickness at the measurement point of interest based on a peak position which appears in a power spectrum obtained through the Fourier transform, and
aggregate film thicknesses determined for a plurality of the measurement points and outputting a resultant aggregate as a film thickness distribution.
4. The optical measurement apparatus according to claim 2 , wherein
the wave number is calculated in consideration of wavelength-dependency of a refractive index of the measurement target.
5. The optical measurement apparatus according to claim 1 , wherein
the modification factor includes a value representing magnitude of an angle of incidence corresponding to each measurement point, and
the second calculation module is configured to
adopt a film thickness at each measurement point as a fluctuating parameter and calculate a theoretical value of each pixel corresponding to the two-dimensional image based on a refractive index of the measurement target, a value representing magnitude of the angle of incidence corresponding to each measurement point, and correspondence between each measurement point and a pixel position in the two-dimensional image, and
determine a film thickness at each measurement point by adjusting the fluctuating parameter such that a similarity between the calculated theoretical value of each pixel and each pixel value of the two-dimensional image is higher.
6. An optical measurement method comprising:
linearly irradiating a measurement target with measurement light having a certain wavelength range and receiving linear measurement interference light which is transmitted light or reflected light originating from the measurement target as a result of irradiation with the measurement light;
expanding the measurement interference light in a wavelength direction orthogonal to a longitudinal direction of the measurement interference light and outputting a two-dimensional image by receiving the measurement interference light expanded in the wavelength direction;
calculating a modification factor depending on an angle of incidence from each measurement point in association with a region in the two-dimensional image corresponding to each measurement point in the measurement target irradiated with the measurement light; and
calculating optical characteristics of the measurement target by applying a corresponding modification factor to each pixel value included in the two-dimensional image.
7. The optical measurement method according to claim 6 , wherein
the modification factor includes a wave number representing a parameter including a wavelength of the measurement light and a refractive index of the measurement target, and
the wave number is calculated in consideration of magnitude of a corresponding angle of incidence, for each pixel position in the two-dimensional image.
8. The optical measurement method according to claim 7 , wherein
the calculating optical characteristics includes
subjecting a row of values resulting from conversion in accordance with a relational expression for linearizing the pixel value of the two-dimensional image corresponding to a measurement point of interest with respect to a phase factor, to Fourier transform with respect to a row of corresponding wave numbers,
determining a film thickness at the measurement point of interest based on a peak position which appears in a power spectrum obtained through the Fourier transform, and
aggregating film thicknesses determined for a plurality of the measurement points and outputting a resultant aggregate as a film thickness distribution.
9. The optical measurement method according to claim 7 , wherein
the wave number is calculated in consideration of wavelength-dependency of a refractive index of the measurement target.
10. The optical measurement method according to claim 6 , wherein
the modification factor includes a value representing magnitude of an angle of incidence corresponding to each measurement point, and
the calculating optical characteristics includes
adopting a film thickness at each measurement point as a fluctuating parameter and calculating a theoretical value of each pixel corresponding to the two-dimensional image based on a refractive index of the measurement target, a value representing magnitude of the angle of incidence corresponding to each measurement point, and correspondence between each measurement point and a pixel position in the two-dimensional image, and
determining a film thickness at each measurement point by adjusting the fluctuating parameter such that a similarity between the calculated theoretical value of each pixel and each pixel value of the two-dimensional image is higher.