Resist-based polarization monitoring with phase-shift masks at 1.35 numerical aperture: Tool-to-tool comparison

Abstract

Experimental results of tool-to-tool polarization comparison at hyper numerical aperture with POLARISTM PSM Polarimetry (Polarization Affected Resist Image Sensor) are presented. Measurements of tool-to-tool variation of the Intensity in the Preferred Polarization State (IPS) are shown with two modes of operation: 1) measurement of relative IPS difference between tools, which does not require calibration with on-board metrology and 2) estimate of actual IPS measurement, which requires calibration with on-board technique. Relative tool-to-tool variation is generally more important, as it, rather than actual IPS values, determines any induced tool-to-tool CD variation. Monitoring single tool stability has been shown in previous work to remain stable to within a fraction of 1%. Tool-to-tool monitoring has additional sources of variation. The example shown illustrates matching with on-board metrology generally within 2%, but up to 4% at a maximum. Some causes of these potential variations are discussed as well as strategies to improve accuracy. The impact of metrology-induced resist burning is assessed and believed to cause uncertainty in the measurement less than 1%. Finally, a set of measurements comparing azimuthal and horizontal-vertical polarization states are shown, illustrating the capability of POLARISTM to report the polarization behavior at arbitrary locations within the pupil. Although pupil-averaged IPS values match to the on-board technique within 1.2%, the angular resolved measurements do not necessarily match theoretical values and vary by up to 10%. © 2010 Copyright SPIE - The International Society for Optical Engineering.