Patent ID: 7411665

Claim:
A method for wavelength calibration of an optical measurement system having a spectrophotometer and a ellipsometer, comprising the steps of: calibrating the spectrophotometer and the ellipsometer being independently of one another in an initial calibration, ascertaining upon calibration of the spectrophotometer, an allocation of the wavelength (λ) incident onto a CCD chip to the position of the pixels of the CCD chip, determining a layer thickness (d elli ) of a specimen using the ellipsometer, as a reference measured value; determining a spectrophotometer layer thickness (d vis photo ) in the visual spectral region and a spectrophotometer layer thickness (d UV photo ) in the UV region, at an initial angle of incidence (θ init ); modifying coefficients of a wavelength-dependent function until the absolute value of the difference between a re-measured visual spectrophotometer layer thickness (d vis photo ) and a re-measured UV spectrophotometer layer thickness (d UV photo ) is less than a predefined absolute value; and varying the initial angle of incidence (θ init ) until the absolute value of the difference between the visual spectrophotometer layer thickness (d vis photo ) and the ellipsometer layer thickness (d elli ), and the absolute value of the difference between the UV spectrophotometer layer thickness (d UV photo ) and the ellipsometer layer thickness (d elli ), are less than a predefined absolute value.