METHODS OF DETERMINING A MECHANICAL PROPERTY OF A LAYER APPLIED TO A SUBSTRATE, CONTROL SYSTEM FOR A LITHOGRAPHIC APPARATUS AND LITHOGRAPHIC APPARATUS

Disclosed is a method for determining a mechanical property of a layer applied to a substrate and associated control system for controlling a lithographic process. The method comprises measuring out-of-plane deformation of the substrate, the out-of-plane deformation comprising deformation normal to a substrate plane defined by, or parallel to, the substrate surface. The measured out-of-plane deformation is fitted to a second order polynomial in two coordinates associated with the substrate plane and the mechanical property (e.g. anisotropic Young's moduli) of the layer is determined based on characteristics of the fitted second order polynomial. The mechanical property of the layer can be used to calibrate an in-plane distortion model of the substrate for predicting in-plane distortion based on the measured out-of-plane deformation.