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 SE, M 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 will be 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 will be seen a high correlation result in the paper as well.