Embodiments of the present disclosure generally relate to apparatus and methods for performing photolithography processes. In one embodiment, a system including multiple interferometers for accurately measuring the location of a substrate during operation is provided. The system may include two chucks, and the two chucks are aligned in a first direction. The interferometers are placed along the first direction to measure the location of the substrate with respect to the first direction. The reduced distance between the interferometers and the chuck improves the accuracy of the measurement of the location of the substrate. In another embodiment, mask pattern data is provided to the system, and the mask pattern data is modified based on location and position information of the substrate. By controlling the mask pattern data with the location and position information of the substrate, less positional errors of the pattern formed on the substrate can be achieved.