Wafer exposure method using wafer models and wafer fabrication assembly

For a wafer exposure method, critical dimension values are obtained from wafer structures at predefined measurement sites. Position-dependent process parameters of an exposure process used for forming the wafer structures are obtained. From the critical dimension values at the measurement sites, coefficients of a preset model and at least one further model are determined. Each further model differs in at least one term from the preset model and from the other models. The models approximate the critical dimension values, the process parameters and/or correction values of the process parameters as a function of at least two position coordinates. Residuals between approximated critical dimension values obtained from the models and the critical dimension values obtained at the measurement sites are determined. Among the preset model and the at least one further model an updated model is selected. The selection is based on a criterion weighting the residuals, the number of terms of the model and/or the order of th