<title>Metrology algorithms for machine matching in different CD SEM configurations</title>

Abstract

Within semiconductor companies, there may be many different critical dimension (CD) measurement instruments. They could be optical, electrical, confocal laser, or scanning electron microscopes (SEM). Often times, they are not only different configurations, but different brands as well. These variations of type and brand have created the need for a measurement algorithm that has the ability to deliver the same measurement between two instruments. It is possible the development group within a semiconductor company would use a CD SEM with expanded capabilities when compared to the production group's CD SEM. In this case, a measurement algorithm unaffected by the differences in signal outputs from the varying microscope designs would enhance system matching. One would believe that two identical CD systems should produce nearly the same measurement. However, when two totally different systems are compared, only a robust algorithm would give good machine to machine matching of measurements. This paper examines two measurement algorithms using two completely different CD and inspection SEMs. The purpose is to examine the algorithm's ability to deliver good machine to machine matching regardless of how the secondary waveform signal is generated.