24 March 2006 Investigation on polarization monitoring mask: pattern design and experimental verification
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Since numerical aperture (NA) becomes greater than 1.0 in immersion lithography, polarization effect will be one of the critical issues in imaging performance. In patterning 40nm or smaller node with 193nm wavelength, transverse magnetic (TM) polarized beam does not contribute to image contrast. Hence most layers will require polarization controlled illumination to prevent the contrast degradation. For this reason, polarization controllability of illumination becomes one of considerable budget of critical dimension (CD) variation. For CD uniformity control of exposure tool and CD budget analysis, it is necessary to measure the polarization performance of illumination system. In-situ or special measurement tools are currently being developed to measure the polarization state of illumination and projection optics. However, each tool maker has its own measurement tool, and consequently in order to compare the polarization performance across different tools, a common measurement method is required. In this paper, a special mask pattern for monitoring polarization state of illumination has been designed. The polarization degrees have been measured for polarized illuminations of 193nm high NA tool. The pattern shape has been designed based on electric magnetic field (EMF) simulation utilizing the diffraction efficiency difference. The actual mask pattern sizes are measured to correct the measurement error. Differences between the EMF simulation and the real exposure results have been investigated for several illumination shapes and for different polarization status.
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Chan Hwang, Chan Hwang, Dong-Woon Park, Dong-Woon Park, Jang-Ho Shin, Jang-Ho Shin, Dong-Seok Nam, Dong-Seok Nam, Suk-Joo Lee, Suk-Joo Lee, Sang-Gyun Woo, Sang-Gyun Woo, Han-Ku Cho, Han-Ku Cho, Joo-Tae Moon, Joo-Tae Moon, "Investigation on polarization monitoring mask: pattern design and experimental verification", Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61521M (24 March 2006); doi: 10.1117/12.657054; https://doi.org/10.1117/12.657054


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