Scatterometry with nanometer sensitivity for non-destructive quality inspection of gratings and thin films

Maintaining structural uniformity in nano-gratings is essential for high production yields, as minor deviations can degrade device performance. Traditional inspection methods like scanning electron microscopy and atomic force microscopy offer precise nanoscale measurements but are hindered by low throughput and the need to destroy samples for cross-sectional analysis, making them unsuitable for large-scale production. To overcome these limitations, an innovative scatterometry technique using Fourier microscopy is introduced. This non-destructive, high-throughput method achieves single-nanometer precision in critical dimension (CD) metrology by illuminating the sample with a controlled incidence angle via a back-focal plane-focused light beam. By analyzing the diffracted light orders at various angles, the technique accurately extracts optical performance and geometrical characteristics of gratings or films, such as line width, height, spacing, and residual layer thickness. Demonstrated through dense scanning of grating patches, this method enables rapid mapping of structural uniformity across wafers, enhancing production yields by identifying fabrication defects.