Recently, extremely-high-quality-quartz substrates have been demanded for advancing ArF-lithography. HOYA has
developed a novel inspection method for interior defects as well as surface defects. The total internal reflection of the
substrate is employed to produce an ideal dark field illumination. The novel inspection method can detect a "nano-pit" of
12nm-EDS, the Equivalent of the Diameter of a Sphere (EDS). It will meet the sensitivity for 32nm node and beyond.
Moreover, a type of unique defect is detected, which induces Serious Transmittance Error for Arf-LiTHography. We call it
the "STEALTH" defect. It is a killer defect in wafer printing; but it cannot be detected with any conventional inspection in
the mask-making process so far.
In this paper, the performance of the novel inspection method for quartz substrates and the investigation of "STEALTH" are reported.