Critical dimension control in photolithography based on the yield by a simulation program

The critical dimension (CD) of wafers in photolithography is the most important parameter that determines the final performance of devices. The sampling of CD’s, as a result, is essential and must be taken with caution. Process yield is a common criterion used in the manufacturing industry for measuring process performance. A measurement index, called Spk, has been proposed to calculate the yield for normal processes, and can be used to establish the relationship between the manufacturing specifications and the actual process performance, which provides an exact measure on process yield. In this paper, we solve the CD control problem based on the yield index Spk. 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 results indicate that a sample size greater than 145 is sufficient to ensure that the decisions made are insensitive to the process precision and the process accuracy. The investigation is useful to the practitioners for making reliable decisions in testing process performance of a stepper and quality of an engineering lot by CD control.