1. A computer program for determining a corrected position of an alignment mark on a substrate to be exposed in a lithographic projection apparatus, said computer program comprising program code, when executed on a computer system, instructing the computer system to perform: controlling a measuring tool to measure the position of at least one alignment mark on said substrate overlaid with an Al layer; calculating a corrected position of the alignment mark on the basis of the measured position of the alignment mark and a model of a process apparatus involved in deposition of the Al layer.