Extraction of critical dimension reference feature CDs from new test structure using HRTEM imaging

The National Institute of Standards and Technology (NIST) is completing a project to provide the semiconductor industry with critical dimension CD reference materials, using the silicon (111) lattice spacing as a reference to establish the linewidth. Recent developments include both a new test structure design as well as changes to the high-resolution transmission electron microscopy (HRTEM) sample preparation and fringe counting procedures. These changes contribute to an improvement over earlier work, in which overall uncertainties of 10 nm to 15 nm were observed for approximately 100 nm wide features; in the current work, overall uncertainties of less than 2 nm have been observed for features as narrow as 40 nm.