Metal Layer Monitoring in DRAM Production by use of Spectroscopic Ellipsometry-based Scatterometry

Current available metrology methods for metal layer line monitoring could include atomic force microscopic (AFM) scanning for trench depth measurement and top-down secondary electron microscope for CD measurement (CD-SEM). However, they both suffer from incomplete information outputs and repeatability issue. Transmission electron microscope (TEM) cross-sections and SEM cross-sections are the two major techniques for obtaining detailed profile information. However, both they are destructive and time-consuming. Scatterometry comes in as a potential process-monitoring candidate for the metal layer process. In this work, we use SE-based scatterometry to demonstrate a two-dimensional profile of the metal trench profile with post-etched structure, as well as CD and depth measurements of the trench. Theory and measurement results of dense structure are briefly discussed. These results are correlated to SEM cross-sections, AFM measurements and CD-SEM measurements. The data shows high correlation between them. Moreover, WAT data were seen a high correlation result in the paper as well