  This article presents the extension of the one-dimensional Stoney algorithm
to a two-dimensional case. The proposed extension consists in modifying the
method of curvature estimation. The surface profile of the wafer before
deposition of the thin film and after its deposition was locally approximated
by the quadric. From this quadric, a quadratic form and the first degree
surface were separated. An eigenproblem was solved for the matrix of this
quadratic form. From eigenvectors a new coordinate system was created in which
a new formula of the quadric was found. In this new coordinate system, the
two-dimensional problem of estimating the curvature tensor has been solved by
solving two independent one-dimensional problems of curvature estimation.
Returning to the primary coordinate system, in this primary coordinate system,
a solution to the two-dimensional problem was obtained. The article proposed
five versions of the two-dimensional Stoney algorithm, with diverse complexity
and accuracy. The recommendation for the version of the algorithm that could be
practically used was also presented.
