Abstract: Multiple scanner or stepper machines are provided. A photoresist layer is coated on a monitor wafer. The photoresist layer is exposed through a mask pattern on a first of the multiple machines. The mask pattern is shifted by an offset and the photoresist layer is exposed through the mask pattern on another of the multiple machines. The shifting and exposing steps are continued for each of the multiple machines. A pattern on the monitor wafer is measured using an overlay measurement tool. Machine constants for each machine except the first machine of the multiple machines are updated based on results of the measuring to provide overlay control machine matching.