When projected with a scanner, the latent image intensity in the photoresist has a slope that can be much lower than
with an interferometer. To study finely the lithographic process and to be predictive, the Normalized image slope of 193
nm immersion interferometer built at LETI has to be controlled. The exposure latitude (EL), the Normalized Image Log
Slope (NILS) and the interference contrast are closely related.
In this paper, we present an immersion interferometer specially designed to be used with a commercial ArF excimer laser. Different configurations are presented enabling the printing of dense lines with a pitch down to 65 nm with an acceptable depth-of-focus. Photoresist patterns are shown at a half-pitch down to 40 nm with nice squared profiles. First polarization studies at high-numerical aperture (NA) have been performed and we noticed a good correlation between roughness and polarization variation at high NA.