Monitoring polarization at 193nm high-numerical aperture with phase shift masks: Experimental results and industrial outlook

This paper will provide experimental results of Phase-Shift Mask (PSM) Polarimetry, a previously introduced resist-based polarization monitoring technique that employs a specialized chromeless phase-shifting test reticle. The patterns derived from high-NA proximity effects have proven to be 2 to 3 times more sensitive to polarization than a previously reported generation of patterns. Example results in this paper show that for a numerical aperture (NA) of 0.93, this technique is likely capable of measuring the intensity in the preferred polarization state (IPS) to within about 3%. Data from a follow-on reticle for NAs up to 1.35 is expected soon and promises to measure IPS to within about 1.5%. This is expected to suffice for monitoring polarization at the 22nm node for water-based immersion tools over time or from tool to tool. This technique is extendable and likely offers even greater sensitivity for high-index immersion lithography, should NAs greater than 1.35 become available. Advantages and disadvantages of this technique will be addressed.