Patent ID: 8338194

Claim:
A method for in situ determination of a material composition of optically thin layers that are deposited from a vapor phase onto a substrate, there being an interferometrically analyzable correlation among optical layer parameters, the optical layer parameters including a wavelength-independent real layer thickness and a complex refractive index having as a real part a refractive index and as an imaginary part an absorption coefficient, the method comprising: irradiating the substrate on a deposition side with incoherent light of at least three different wavelengths in a visible optical region during a deposition process; optically detecting in a spatially resolved manner a reflection intensity of a diffuse or a direct light scattering emanating from a deposited layer outside of a total reflection in the at least three different wavelengths; concurrently with the optically detecting, providing numerical values of the detected reflection intensity to an optical layer model based on a general line transmission theory in which the deposited layer is interpreted as being an electromagnetic conductor having a variable field wave impedance, a propagation constant and the wavelength-independent real layer thickness that is equivalent to the conductor length; ascertaining values for the optical layer parameters of the deposited layer front the optical layer model for the at least three different wavelengths by numerically adapting the optical layer model to a time characteristic of the detected reflection intensities, the wavelength-independent real layer thickness being used as a reference value; and quantitatively determining a material composition of the deposited layer front the ascertained values of the optical layer parameters by comparing the ascertained values to standard values for optical layer parameters of known material compositions.