It is important to understand how a photomask will polarize incident radiation. This paper presents data collected on binary mask and various attenuated phase shifting mask materials, feature sizes, duty ratios, and illumination schemes via rigorous coupled wave analysis, extinction spectroscopy, and 193nm lithographic evaluation. Additionally, the result of polarization effects due to the photomask on imaging has been studied. It was found that in the majority of the cases, higher NA led to greater polarization effects. All mask materials predominantly pass the TM polarization state for the 0 order, whereas different materials and duty ratios affect the polarization of the first diffracted orders differently. The polarization effects contributed by mask materials being considered for use in high NA imaging systems need to be examined. The degree of polarization as a function of n and k is presented, providing an introduction to the desirable properties of future mask materials. Materials with higher refractive indices and lower extinction coefficients tend to pass more of the TM polarization state, which is undesirable. Materials with lower indices and relatively wide range of extinction coefficients pass more TE polarized radiation. The duty ratio, critical dimension, mask material, material thickness, and illumination scheme all influence mask induced polarization effects.
Date of creation, presentation, or exhibit
Department, Program, or Center
Mechanical Engineering (KGCOE)
Andrew Estroff, Yongfa Fan, Anatoly Bourov, Bruce William Smith, "Mask-induced polarization effects at high numerical aperture," Journal of Micro/Nanolithography, MEMS, and MOEMS 4(3), 031107 (1 July 2005). https://doi.org/10.1117/1.2037507
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