Method of measuring a thickness of a multilayered sample using ultraviolet light and light with wavelengths longer than ultraviolet

Claim 1

A method of measuring thicknesses d1, d2 and d3 of a transparent insulation film, a silicon film and a transparent film, respectively, of a multilayered sample object which is formed by disposing said transparent film on an SOI substrate which is comprised of a body, said transparent insulation film and said silicon film, said method comprising: a first step of irradiating said multilayered sample object with light of first and second wavelength ranges to thereby measure spectral reflectance, said first wavelength range being a ultraviolet range, said second wavelength range including longer wavelengths than the ultraviolet range; a second step of calculating the thickness d3 of said transparent film from the measured spectral reflectance of the first wavelength range; a third step of calculating reflectance against wave numbers at equal wave number intervals from the measured spectral reflectance of the second wavelength range, and frequency converting the calculated reflectance to thereby develop a frequency converted spectrum; a fourth step of obtaining a power spectrum from the frequency converted spectrum to find a peak which expresses interference caused by said silicon film in the power spectrum, and calculating an approximate value d2' of the thickness of said silicon film based on the location of the peak and an average refractive index of silicon in a wave number space; a fifth step of eliminating periodic components corresponding to a certain effective optical path or longer paths in the frequency converted spectrum by low-pass filtering to thereby obtain a filtered frequency converted spectrum, then calculating intermediate spectral reflectance against wavelengths at equal wavelength intervals from the filtered frequency converted spectrum, then theoretically deriving theoretical spectral reflectance of when only said transparent film of the thickness d3 is formed on a silicon layer, the thickness d3 being a value which is calculated at said second step, then subtracting the theoretical spectral reflectance from the intermediate spectral reflectance to thereby obtain final spectral reflectance for the second wavelength range and then calculating an approximate value d1' of the thickness of said transparent insulation film from the final spectral reflectance; a sixth step of changing the thicknesses d1 and d2 from said approximate values d1' and d2' each by a fixed amount and calculating deviations between the theoretical spectral reflectance and the measured spectral reflectance with respect to the thicknesses d1, d2 and d3 to thereby find a combination (d1, d2) having the minimum deviation, the thickness d3 being a value which is calculated at said second step; and a seventh step of performing nonlinear optimization on the thicknesses d1 and d2 of said combination (d1, d2) which is found at said sixth step, thereby finally determining the thicknesses d1 and d2 as the thicknesses of said transparent insulation film and said silicon film.

Claim 2

A method of measuring thicknesses d1, d2 and d3 of a transparent insulation film, a silicon film and a transparent film, respectively, of a multilayered sample object which is formed by disposing said transparent film on an SOI substrate which is comprised of a body, said transparent insulation film and said silicon film, said method comprising: a first step of irradiating said multilayered sample object with light of first and second wavelength ranges to thereby measure spectral reflectance, said first wavelength range being a ultraviolet range, said second wavelength range including longer wavelengths than the ultraviolet range; a second step of calculating the thickness d3 of said transparent film from the measured spectral reflectance of the first wavelength range; a third step of calculating reflectance against wave numbers at equal wave number intervals from the measured spectral reflectance of the second wavelength range, and frequency converting the calculated reflectance to thereby develop a frequency converted spectrum; a fourth step of obtaining a power spectrum from the frequency converted spectrum to find a peak which expresses interference caused by said silicon film in the power spectrum, and calculating an approximate value d2' of the thickness of said silicon film based on the location of the peak and an average refractive index of silicon in a wave number space; a fifth step of eliminating periodic components corresponding to a certain effective optical path or longer paths in the frequency converted spectrum by low-pass filtering to thereby obtain a filtered frequency converted spectrum, then calculating intermediate spectral reflectance against wavelengths at equal wavelength intervals from the filtered frequency converted spectrum, then theoretically deriving theoretical spectral reflectance of when only said transparent film of the thickness d3 is formed on a silicon layer, the thickness d3 being a value which is calculated at said second step, then subtracting the theoretical spectral reflectance from the intermediate spectral reflectance to thereby obtain final spectral reflectance for the second wavelength range and then calculating an approximate value d1' of the thickness of said transparent insulation film from the final spectral reflectance; a sixth step of changing the thicknesses d1 and d2 from said approximate values d1' and d2' each by a fixed amount and calculating deviations between the theoretical spectral reflectance and the measured spectral reflectance with respect to the thicknesses d1, d2 and d3 to thereby find a combination (d1, d2) having the minimum deviation, the thickness d3 being a value which is calculated at said second step; and a seventh step of performing nonlinear optimization on the thicknesses d1 and d2 of said combination (d1, d2) which is found at said sixth step, thereby finally determining the thicknesses d1 and d2 as the thicknesses of said transparent insulation film and said silicon film.

Claim 5

A method of measuring thicknesses d1, d2, d3 and d4 of a transparent insulation film, a silicon film and first and second transparent films, respectively, of a multilayered sample object which is formed by disposing said first and said second transparent films in this order on an SOI substrate which is comprised of a body, said transparent insulation film and said silicon film, said method comprising: a first step of irradiating said multilayered sample object with light of first and second wavelength ranges to thereby measure spectral reflectance, said first wavelength range being a ultraviolet range, said second wavelength range including longer wavelengths than the ultraviolet range; a second step of calculating the sum of effective optical path lengths of said first and said second transparent films from the measured spectral reflectance of said first wavelength range to find the maximum values d3max and d4max of the thicknesses d3 and d4, then tentatively determining the thicknesses d1 and d2 both as zero, then changing the thicknesses d3 and d4 each by a fixed amount from zero to said maximum values d3max and d4max to calculate deviations between theoretical spectral reflectance and the measured spectral reflectance with respect to the thicknesses d1, d2, d3 and d4, then finding a combination (d3, d4) having the minimum deviation, and thereafter performing nonlinear optimization on the thicknesses d3 and d4 of said combination (d3, d4) and finally determining the thicknesses d3 and d4 as the thicknesses of said first and said second transparent films; a third step of calculating reflectance against wave numbers at equal wave number intervals from the measured spectral reflectance of said second wavelength range and frequency converting the calculated reflectance to thereby develop a frequency converted spectrum; a fourth step of obtaining a power spectrum from the frequency converted spectrum to find a peak which expresses interference caused by said silicon film in the power spectrum, and calculating an approximate value d2' of the thickness of said silicon film based on the location of the peak and an average refractive index of silicon in a wave number space; a fifth step of eliminating periodic components corresponding to a certain effective optical path or longer paths in the frequency converted spectrum by low-pass filtering to thereby obtain a filtered frequency converted spectrum, then calculating intermediate spectral reflectance against wavelengths at equal wavelength intervals from the filtered frequency converted spectrum, then theoretically deriving theoretical spectral reflectance of when only said transparent film of the thickness d3 is formed on a silicon layer, the thickness d3 being a value which is calculated at said second step, then subtracting the theoretical spectral reflectance from the intermediate spectral reflectance to thereby obtain final spectral reflectance for the second wavelength range and then calculating an approximate value d1' of the thickness of said transparent insulation film from the final spectral reflectance; a sixth step of changing the thicknesses d1 and d2 from said approximate values d1' and d2' each by a fixed amount, and calculating deviations between the theoretical spectral reflectance and the measured spectral reflectance with respect to the thicknesses d1, d2, d3 and d4 to thereby find a combination (d1, d2) having the minimum deviation; and a seventh step of performing nonlinear optimization on the thicknesses d1 and d2 of said combination (d1, d2) which is found at said sixth step, thereby finally determining the thicknesses d1 and d2 as the thicknesses of said transparent insulation film and said silicon film.

Claim 6

A method of measuring thicknesses d1, d2, d3 and d4 of a transparent insulation film, a silicon film and first and second transparent films, respectively, of a multilayered sample object which is formed by disposing said first and said second transparent films in this order on an SOI substrate which is comprised of a body, said transparent insulation film and said silicon film, said method comprising: a first step of irradiating said multilayered sample object with light of first and second wavelength ranges to thereby measure spectral reflectance, said first wavelength range being a ultraviolet range, said second wavelength range including longer wavelengths than the ultraviolet range; a second step of calculating the sum of effective optical path lengths of said first and said second transparent films from the measured spectral reflectance of said first wavelength range to find the maximum values d3max and d4max of the thicknesses d3 and d4, then tentatively determining the thicknesses d1 and d2 both as zero, then changing the thicknesses d3 and d4 each by a fixed amount from zero to said maximum values d3max and d4max to calculate deviations between theoretical spectral reflectance and the measured spectral reflectance with respect to the thicknesses d1, d2, d3 and d4, then finding a combination (d3, d4) having the minimum deviation, and thereafter performing nonlinear optimization on the thicknesses d3 and d4 of said combination (d3, d4) and finally determining the thicknesses d3 and d4 as the thicknesses of said first and said second transparent films; a third step of calculating reflectance against wave numbers at equal wave number intervals from the measured spectral reflectance of said second wavelength range and frequency converting the calculated reflectance to thereby develop a frequency converted spectrum; a fourth step of obtaining a power spectrum from the frequency converted spectrum to find a peak which expresses interference caused by said silicon film in the power spectrum, and calculating an approximate value d2' of the thickness of said silicon film based on the location of the peak and an average refractive index of silicon in a wave number space; a fifth step of eliminating periodic components corresponding to a certain effective optical path or longer paths in the frequency converted spectrum by low-pass filtering to thereby obtain a filtered frequency converted spectrum, then calculating intermediate spectral reflectance against wavelengths at equal wavelength intervals from the filtered frequency converted spectrum, then theoretically deriving theoretical spectral reflectance of when only said transparent film of the thickness d3 is formed on a silicon layer, the thickness d3 being a value which is calculated at said second step, then subtracting the theoretical spectral reflectance from the intermediate spectral reflectance to thereby obtain final spectral reflectance for the second wavelength range and then calculating an approximate value d1' of the thickness of said transparent insulation film from the final spectral reflectance; a sixth step of changing the thicknesses d1 and d2 from said approximate values d1' and d2' each by a fixed amount, and calculating deviations between the theoretical spectral reflectance and the measured spectral reflectance with respect to the thicknesses d1, d2, d3 and d4 to thereby find a combination (d1, d2) having the minimum deviation; and a seventh step of performing nonlinear optimization on the thicknesses d1 and d2 of said combination (d1, d2) which is found at said sixth step, thereby finally determining the thicknesses d1 and d2 as the thicknesses of said transparent insulation film and said silicon film.