Patent ID: 7046379

Claim:
A characterisation or control method for preparation of a thin layer component according to optical methods wherein: signals S 1 and S 2 related to the thickness x and to the complex optical index of the component for a wavelength λ are measured and acquired, the signals S 1 and S 2 thus acquired are processed in order to obtain parameters x, ∈ of the layers deposited, characterised in that: the stacking is represented by the product of two Abeles matrices for each polarisation direction s (perpendicular to the plane of incidence) and p (parallel to the plane of incidence): a matrix Mo s,p known representing the support, a matrix dM s,p representing a thin transparent layer being deposited, the inversion of the variations of the measured signals dS 1 , dS 2 enables to get the thickness x and the dielectric constant ∈ of the thin layer using the following operations: Taylor development in relation to the variation dx of the thickness x of the thin layer of the coefficients of the matrix dM, calculation of the coefficients of the matrix M s,p each in the form A(∈ ±2 )dx 2 +B(∈ ±1 )dx+C deducing therefrom the relation S 1,2 =A 1,2 (∈ ±2 ) dx 2 +B 1,2 (∈ ±1 ) dx+C 1,2 linking the signals S 1 and S 2 to the parameters ∈ and dx, eliminating dx, deducing therefrom a master function P (∈ ±4 )=0 solving the equation using an appropriate method, selecting the solutions of this equation corresponding to values physically plausible, to measure ∈, using the value ∈ obtained to determine dx.