Enabling the 45nm node by hyper-NA polarized lithography

The introduction of immersion step and scan systems has opened the road for hyper-NA lenses (NA > 1). At these NA's polarization control becomes a key parameter in imaging. Application of polarized illumination leads to an increase of contrast and exposure latitude. The resulting resolution enhancement offered by polarized illumination enables 45nm node lithography with an ArF, NA=1.2 system. Hyper-NA systems utilizing polarized illumination must be fully compatible with all requirements for a volume production tool: maintaining imaging performance at full throughput, overlay and focus control; flexibility and ease-of-use are essential features. Adequate polarization control is realized by employing polarization-preserving optics, and by automated in-line metrology to optimize the system for any selected polarization state. In this paper we address the improvements of polarization for the 65nm and 45nm imaging node applications. Experimental results describing the imaging effects while using polarized illumination on high-NA (NA=0.93) and hyper-NA (NA=1.2) exposure tools will be shown. These data will also be compared to simulations. In addition, this paper includes a short section that deals with the issues of reticle birefringence. Finally, system control and in-line metrology under high-volume production conditions will be discussed.