On the Fly Ellipsometry Imaging for Process Deviation Detection

Spectroscopic ellipsometry is a very sensitive optical metrology technique commonly used in semiconductor manufacturing lines to accurately measure the thickness and refractive index of different layers present on specific dedicated metrology targets on the wafers. In parallel, optical defectivity techniques are widely implemented in production lines to inspect a significant amount of dies representative of the full wafer and detect physical and patterning defects. A new approach can then simply emerge which is to apply ellipsometry metrology techniques at a full or die wafer scale. This strategy, at the frontier between metrology and defectivity field is expected to bring solutions for certain types of process deviation. In our case, ellipsometry's optical response was collected on large areas of product wafers to capture specific deviations such as film properties, thickness, and patterning variation. This is an innovative strategy that relies on a model-less approach to detect process drifts, using ellipsometry's sensitivity to material properties and design architecture variations. In this paper, we will present this approach on three industrial cases.