Spectrophotometry and beam profile reflectometry measurement of six layers in an SOI film stack

We developed a robust measurement recipe for six layer SOI film stack. Both spectrometer and BPR were combined to characterize the plate and storage polysilicons. A new global optimization method was developed to find the best solution in parameter spaces with up to 12 parameters. Such a recipe was applied to production wafers with over 50 site die mapping. The 5 day repeatability shows the measurements were stable and robust.