New process monitor for reticles and wafers: the MEEF meter

In this paper, we present experimental results with a prototype design of a 'MEEF Meter,' and investigate its sensitivity to defocus and exposure changes. We find that the results of the MEEF meter complement the results obtained through conventional CD metrology, with conventional CDs being a good indicator of exposure changes, while the MEEF meter is a good indicator of defocus changes. We also investigate two kinds of MEEF meter, a dense MEEF meter and 'Process' MEEF meter design, and find the results for MEEF similar, but that the 'Process' MEEF meter design is far more susceptible to noise and bridging.