On the solution of a metrology problem in semiconductor manufacturing using shape analysis

This paper presents an efficient numerical technique to reconstruct the profile of one-dimensional gratings from ellipsometry measurements, that is, the ratio of reflection coefficients between the two basic polarizations. The basic idea is to use gradient-based optimization methods to create a minimizing sequence of profiles by iteratively changing its geometric parameters. The gradients with respect to the parameters are computed efficiently using adjoints of the electromagnetic fields. One possible application of this technique is in semiconductor metrology.