Provided is an integrated circuit (IC) manufacturing method. The method includes receiving a design layout of an IC, the design layout having a main feature; performing a process correction to the main feature thereby generating a modified main feature; using a computer, generating a simulated contour of the modified main feature, the simulated contour having a plurality of points; generating a plurality of assistant data in computer readable format, wherein each assistant data includes at least one process performance factor associated with one of the points; and keeping the simulated contour and the assistant data for use by a further process stage, such as mask making, mask inspection, mask repairing, wafer direct writing, wafer inspection, and wafer repairing.