Apparatus and method for measuring thickness of thin semiconductor multi-layer film

Claim 1

An apparatus for measuring thicknesses of layers in a thin semiconductor multi-layer film comprising: a first memory for storing refractive index distribution and wavenumber dispersion data for respective layers of a multi-layer film; a spectrometer for continuously measuring spectral distribution of light reflected from an underlying layer of the multi-layer film over a range from visible light to far infrared light; film interference spectrum operating means for eliminating optical transmission characteristics of the spectrometer from the spectral distribution measured by the spectrometer and producing an interference spectrum including only multi-layer film interference components; a second memory for storing the interference spectrum including only multi-layer film interference components produced by the film interference spectrum operating means; Spatialgram calculating means for reverse Fourier transforming a wavenumber range of an interference spectrum excluding the optical transmission characteristics of the spectrometer and calculating a Spatialgram; a third memory for storing the Spatialgram calculated by the Spatialgram calculating means; layer thickness approximate value calculating means for reading out side burst peaks of the Spatialgram and the refractive index distribution of respective layers stored in the first memory and calculating approximate respective layer thicknesses; a fourth memory for storing the approximate respective layer thicknesses calculated by the film thickness approximate value calculating means; theoretical interference spectrum calculating means for obtaining a theoretical interference spectrum from a characteristic matrix calculation based on the approximate layer thicknesses, the refractive index distribution of respective films, and the wavenumber dispersion data stored in the first memory; and recalculating means for comparing the measured interference spectrum with the theoretical interference spectrum, changing the layer thicknesses of the respective layers to lessen differences between the measured interference spectrum and the theoretical interference spectrum and recalculating the theoretical interference spectrum to obtain layer thicknesses of high precision.

Claim 2

An apparatus for measuring thicknesses of layers in a thin semiconductor multi-layer film comprising: a first memory for storing refractive index distribution and wavenumber dispersion data for respective layers of a multi-layer film; a spectrometer for continuously measuring spectral distribution of light reflected from an underlying layer of the multi-layer film over a range from visible light to far infrared light; film interference spectrum operating means for eliminating optical transmission characteristics of the spectrometer from the spectral distribution measured by the spectrometer and producing an interference spectrum including only multi-layer film interference components; a second memory for storing the interference spectrum including only multi-layer film interference components produced by the film interference spectrum operating means; Spatialgram calculating means for reverse Fourier transforming a wavenumber range of an interference spectrum excluding the optical transmission characteristics of the spectrometer and calculating a Spatialgram; a third memory for storing the Spatialgram calculated by the Spatialgram calculating means; layer thickness approximate value calculating means for reading out side burst peaks of the Spatialgram and the refractive index distribution of respective layers stored in the first memory and calculating approximate respective layer thicknesses; a fourth memory for storing the approximate respective layer thicknesses calculated by the film thickness approximate value calculating means; theoretical interference spectrum calculating means for obtaining a theoretical interference spectrum from a characteristic matrix calculation based on the approximate layer thicknesses, the refractive index distribution of respective films, and the wavenumber dispersion data stored in the first memory; and recalculating means for comparing the measured interference spectrum with the theoretical interference spectrum, changing the layer thicknesses of the respective layers to lessen differences between the measured interference spectrum and the theoretical interference spectrum and recalculating the theoretical interference spectrum to obtain layer thicknesses of high precision.

Claim 5

A method for measuring the thicknesses of the layers of a thin semiconductor multi-layer film comprising: storing refractive index distribution and wavenumber dispersion data for respective layers of a multi-layer film; continuously spectrally analyzing light reflected from an underlying layer of the multi-layer film over a range from visible light to far infrared light with a spectrometer; producing an interference spectrum by eliminating an optical transmission characteristic of the spectrometer from the spectrally analyzed light, leaving only multi-layer film interference components; storing the interference spectrum of only the multi-layer interference components; calculating a Spatialgram from a reverse Fourier transformation for a limited wavenumber range of the interference spectrum from which the optical transmission characteristic has been eliminated; storing the Spatialgram; reading out side burst peaks of the Spatialgram and refractive index distribution of respective layers and calculating approximate respective layer thicknesses; storing the approximate respective layer thicknesses; calculating a theoretical interference spectrum from a characteristic matrix based on the approximate layer thicknesses, the refractive index distribution, and wavenumber dispersion data of respective layers; and comparing the interference spectrum with the theoretical interference spectrum, changing the layer thicknesses of the respective layers to lessen differences between the measured interference spectrum and the theoretical interference spectrum and recalculating the theoretical interference spectrum to obtain a high precision measurement of the layer thicknesses.

Claim 6

A method for measuring the thicknesses of the layers of a thin semiconductor multi-layer film comprising: storing refractive index distribution and wavenumber dispersion data for respective layers of a multi-layer film; continuously spectrally analyzing light reflected from an underlying layer of the multi-layer film over a range from visible light to far infrared light with a spectrometer; producing an interference spectrum by eliminating an optical transmission characteristic of the spectrometer from the spectrally analyzed light, leaving only multi-layer film interference components; storing the interference spectrum of only the multi-layer interference components; calculating a Spatialgram from a reverse Fourier transformation for a limited wavenumber range of the interference spectrum from which the optical transmission characteristic has been eliminated; storing the Spatialgram; reading out side burst peaks of the Spatialgram and refractive index distribution of respective layers and calculating approximate respective layer thicknesses; storing the approximate respective layer thicknesses; calculating a theoretical interference spectrum from a characteristic matrix based on the approximate layer thicknesses, the refractive index distribution, and wavenumber dispersion data of respective layers; and comparing the interference spectrum with the theoretical interference spectrum, changing the layer thicknesses of the respective layers to lessen differences between the measured interference spectrum and the theoretical interference spectrum and recalculating the theoretical interference spectrum to obtain a high precision measurement of the layer thicknesses.