Patent ID: 7812966

Claim:
A method of determining a depth profile of a surface structure, the method comprising: irradiating the surface structure with irradiation light comprising light components of different wavelengths; and determining the depth profile of the surface structure in dependence on interferometric effects caused by reflection of the irradiation light at the surface structure, wherein intensities of the light components of the reflection of the irradiation light are weighted in dependence on corresponding light component weighting factors, wherein the light component weighting factors are determined by: a) generating an auxiliary surface structure that is identical or similar to the surface structure to be measured, b) irradiating the auxiliary surface structure during its formation with light having a fixed wavelength, c) measuring light reflected by the auxiliary surface structure, d) generating a corresponding auxiliary trend curve in dependence on the measured reflected light, e) carrying out steps b) to d) several times, each time using light having a different fixed wavelength, and f) determining the light component weighting factors in dependence on the auxiliary trend curves determined.