SEMATECH's infrastructure for defect metrology and failure analysis to support its EUV mask defect reduction program

Mask blank defects have been one of the top challenges in the commercialization of extreme ultraviolet (EUV) lithography. To determine defect sources and devise mitigation solutions, detailed characterization of defects is critical. However, small defects pose challenges in metrology scale-up. SEMATECH has a comprehensive metrology strategy to address any defect larger than a 20 nm core size to obtain solutions for defect-free EUV mask blanks. This paper will outline challenges in the metrology of current defects on EUV mask blanks and metrology issues that arise with increasingly smaller defects. Further, we will illustrate SEMATECH's approach and existing capabilities, including a state-of-the-art metrology toolset to analyze EUV mask blank defects. These capabilities include, but are not limited to, Auger spectroscopy and high resolution transmission electron microscopy (TEM) analysis, which enables SEMATECH to study nanoscale defects. The newly established Auger tool at SEMATECH can run a standard 6-inch mask blank and is already providing important information on sub-100 nm defects on EUV blanks. Complementary to Auger analysis, TEM provides ultimate resolution in the defect imaging of sub-nanometer structures. Crystalline and phase information generated by this metrology technique also indicates the sources of defects. SEMATECH's TEM capability is further equipped with energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), which provide higher analytical power than similar techniques in traditional secondary electron microscopy (SEM).