High accuracy, high throughput, and non-destructive optical critical dimension (OCD) metrology has become mainstream in the last several generations of semiconductor development. Its measurements are based on scatterometry to derive shape, dimension and composition information from the scattering patterns observed in light that has interacted with the sample. Onto Innovation’s OCD technology offers powerful and advanced metrology modeling capability, as well as next-generation real-time regression, offline sensitivity analysis, and comprehensive GUI and structure input for true multi-variant modeling. In this talk, the basic concepts of OCD technique will be introduced. The key factors that enable high quality modeling will be discussed. Following this, examples of critical control steps in the manufacturing of Logic, 3DNAND and DRAM devices will be given to demonstrate Onto’s full OCD capability to measure complex three-dimensional structures and challenging process steps with highly repeatable and accurate measurements, and production worthy throughput.