System-level line-edge roughness limits in extreme ultraviolet lithography

As critical dimensions shrink, line-edge roughness (LER) and linewidth roughness become of increasing concern. Traditionally, LER is viewed as a resist-limited effect; however, as critical dimensions shrink and LER requirements become proportionally more stringent, system-level effects begin to play an important role. Recent advanced extreme-ultraviolet resist testing results have demonstrated lower bounds on achievable LER at the level of approximately 2–3nm. Here, the authors use modeling to demonstrate that a significant portion of this low bound may, in fact, be do to system-level effects and, in particular, the mask. Of concern are both LER on the mask as well as roughness of the multilayer reflector. Modeling also shows roughness (flare) in the projection optics not to be of concern.

[1]  D. Stearns,et al.  Practical approach for modeling extreme ultraviolet lithography mask defects , 2002 .

[2]  H. Solak,et al.  Observation of speckle patterns in extreme ultraviolet imaging , 2001 .

[3]  Daniel G. Stearns,et al.  Stochastic model for thin film growth and erosion , 1993 .

[4]  K. Goldberg,et al.  Lithographic characterization of the field dependent astigmatism and alignment stability of a 0.3 numerical aperture extreme ultraviolet microfield optic , 2005 .

[5]  J. Underwood,et al.  Layered synthetic microstructures as Bragg diffractors for X rays and extreme ultraviolet: theory and predicted performance. , 1981, Applied optics.

[6]  J. Goodman.  Statistical Optics , 1985 .

[7]  Kenneth A. Goldberg,et al.  Recent results from the Berkeley 0.3-NA EUV microfield exposure tool , 2007, SPIE Advanced Lithography.

[8]  Patrick P Naulleau.  Relevance of mask-roughness-induced printed line-edge roughness in recent and future extreme-ultraviolet lithography tests. , 2004, Applied optics.

[9]  Gregg M Gallatin,et al.  Line-edge roughness transfer function and its application to determining mask effects in EUV resist characterization. , 2003, Applied optics.

[10]  Kenneth A. Goldberg,et al.  At-wavelength alignment and testing of the 0.3 NA MET optic , 2004 .

[11]  Thomas Schmoeller,et al.  Efficient simulation of light diffraction from three-dimensional EUV masks using field decomposition techniques , 2003, SPIE Advanced Lithography.

[12]  Patrick P Naulleau,et al.  Lithographic characterization of the spherical error in an extreme-ultraviolet optic by use of a programmable pupil-fill illuminator. , 2006, Applied optics.

[13]  P. Naulleau.  The role of temporal coherence in imaging with extreme ultraviolet lithography optics , 2003 .

[14]  D. Stearns,et al.  Nonspecular scattering from extreme ultraviolet multilayer coatings , 2000 .

[15]  Kenneth A. Goldberg,et al.  Status of EUV micro-exposure capabilities at the ALS using the 0.3-NA MET optic , 2004, SPIE Advanced Lithography.

[16]  Costas J. Spanos,et al.  Lithographic characterization of the flare in the Berkeley 0.3 numerical aperture extreme ultraviolet microfield optic , 2006 .

[17]  Zhengrong Zhu,et al.  Rigorous EUV mask simulator using 2D and 3D waveguide methods , 2003, SPIE Advanced Lithography.

[18]  Yunfei Deng,et al.  Extreme ultraviolet mask defect simulation: Low-profile defects , 2000 .