The Value of In-Line Metrology for Advanced Process Control

In-line metrology provides critical information for feedback and feedforward process control. In high-volume manufacturing, the fundamental question is: how fast, how frequent, and how accurate measurements should be made to satisfy control requirements. This paper develops a framework to study the tradeoff among the sampling rate, the delay, and the quality of measurements and the effect of these canonical factors on the variability of processes. As a consequence of this fundamental tradeoff, the relative value of virtual metrology with respect to real metrology can be quantified in the context of advanced process control.