Investigation of polarization effects on new mask materials

Karsten Bubke; Silvio Teuber; Ingo Hoellein; Hans Becker; Holger Seitz; Ute Buttgereit

doi:10.1117/12.599688

12 May 2005 Investigation of polarization effects on new mask materials

Karsten Bubke, Silvio Teuber, Ingo Hoellein, Hans Becker, Holger Seitz, Ute Buttgereit

Proceedings Volume 5754, Optical Microlithography XVIII; (2005) https://doi.org/10.1117/12.599688
Event: Microlithography 2005, 2005, San Jose, California, United States

Abstract

As microlithography moves to smaller critical dimensions, structures on reticles reach feature sizes comparable to the operating wavelength. Furthermore, with increasing NA the angle of incidence of light illuminating the mask steadily increases. In particular for immersion lithography this will have severe consequences on the printing behavior of reticles. Polarization effects arise which have an impact on, among other things, the contrast of the printed image. Angular effects have to be considered when aggressive off-axis illumination schemes are used. Whereas numerous articles have been published on those effects and the underlying theory seems to be understood, there is a strong need for experimental verification of properties of real masks at the actinic wavelength. This paper presents measurements of polarization effects on different mask blank types produced at Schott Lithotec including chrome and alternative absorber binary mask blanks, as well as phase shift mask blanks. Thickness and optical dispersion of all layers were determined using grazing incidence x-ray reflectometry (GIXR) and variable angle spectroscopic ellipsometry (VASE). The set of mask blanks was patterned using a special design developed at the Advanced Mask Technology Center (AMTC) to allow measurements at different line width and pitch sizes. VUV Ellipsometry was then used to measure the properties of the structured materials, in particular the intensities in the 0^th and 1^st diffraction order for both polarization directions and varying angle of incidence. The degree of polarization of respective mask types is evaluated for dense lines with varying pitches and duty cycles. The results obtained experimentally are compared with simulations based on rigorous coupled wave analysis (RCWA).

Citation Download Citation

Karsten Bubke, Silvio Teuber, Ingo Hoellein, Hans Becker, Holger Seitz, and Ute Buttgereit "Investigation of polarization effects on new mask materials", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); https://doi.org/10.1117/12.599688

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