Photolithography, typically taking about one- third of the total wafer manufacturing costs, is one of the most complex operations and is the most critical process in semiconductor manufacturing. Three most important parameters that determine the final performance of devices are critical dimension (CD), alignment accuracy and photoresist (PR) thickness. Process yield, a common criterion used in the manufacturing industry for measuring process performance, can be applied to examine the photolithography process. In this paper, we solve the photolithography production control problem based on the yield index S PK. The critical values required for the hypothesis testing, using the standard simulation technique, for various commonly used performance requirements, are obtained. Extensive simulation results are provided and analyzed. The investigation is useful to the practitioners for making reliable decisions in either testing process performance or examining quality of an engineering lot in photolithography.