Abstract This paper proposes a lithography process control system to handle sub half micron patterning. The system consists of a stepper, coater, and developer. The stepper uses image processing in pattern inspection mode. Through application of the stepper's image processing alignment, the system provides precise apparatus control, including the measurement of positional accuracy, resist sensitivity, resist thickness, focus offset, and development uniformity. Since the stepper controls the overall system, the system itself is relatively inexpensive and extremely simple.