**9. References**


Irradiation Effects on EUV Nanolithography Collector Mirrors 395

Henke, B. L.; Gullikson, E. M.; Davis, J.C. (1993). *X-ray interactions: photoabsorption, scattering,* 

Jurczyk, B. E.; Vargas-Lopez, E.; Neumann, M. N.; & Ruzic, D. N. (2005). *Illinois debris-*

Madi, C. S.; Anzenberg, E.; Ludwig, K.; Aziz M.J. (2011). *Mass Redistribution Causes the Structural Richness of Ion-Irradiated Surfaces,* Physical review letters 106.6, 66101. Möller, W.; Eckstein, W.; Biersack, J.P. (1988). *Tridyn-binary collision simulation of atomic* 

Muñoz-Garcia, J; Vazquez, L.; Cuerno, R.; Sanchez-Garcia, J.; Castro, M.; Gago, R. (2009).

Nieto, M.; Allain, J.P.; Titov, V.; Hendricks, Matthew R.; Hassanein, A.; Rokusek, D.;

O'Connor, A.; Dunne, P.; Morris, O.; O'Reilly, F.; O'Sullivan, G.; & Sokell, E. (2009).

Tarrio, C. & Grantham S. (2005). *Synchrotron beamline for extreme-ultraviolet multilayer mirror* 

Thompson, K. C.; Antonsen, E. L.; Hendricks, M. R.; Jurczyk, B. E.; Williams, M.; &

Van der Velden, M; Lorenz, M. (2008). *Radiation Generated Plasmas: a challenge in modern* 

Van der Velden, M. H. L.; Brok, W. J. M.; van der Mullen, J. J. A. M.; & Banine, V. (2006).

van Herpena, M.M.J.W.; Klundera, D.J.W.; Soera, W.A.; Moorsb, R.; & Banineb, V. (2010). *Sn* 

Vargas López, E.; Jurczyk, B. E.; Jaworski, M.A.; Neumann, M. J.; & Ruzic, D. N. (2005).

multilayer mirror, J. Appl. Phys. 100 (7) 073303, ISSN 1089-7550

Iss. 4-6, Pp. 197-199, (January 2010), ISSN 0009-2614

Tables, Vol. 54, 181-342, Available from: http://henke.lbl.gov/optical\_constants

355-368.

p053510, ISSN: 00218979

Conf. Ser. 163 012116

4

(March 2006), ISSN 0167-9317

(February 2005), ISSN 0167-9317

Issue 2, February 2005, Pages 103-109, ISSN 0167-9317

(Ed.), Springer-Verlag, pp. 323 – 398, ISBN 978-0-387-77716-0

*endurance testing*, Rev. Sci. Instrum. 76, 056101, ISSN 0034-6748

*transmission, and reflection at E=50-30000 eV, Z=1-92*, Atomic Data and Nuclear Data

*mitigation EUV applications laboratory*, Microelectronic Engineering, Volume 77,

*collisions and dynamic composition changes in solids,* Computer Phys. Comm. 51, No. 3,

*Self-Organized Surface Nanopatterning by Ion Beam Sputtering,* in Toward Functional Nanomaterials: Lecture Notes in Nanoscale Science and Technology, Whang, Z

Chrobak, C.; Tarrio, Charles; Barad, Y.; Grantham, S.; Lucatorto, T.B.; Rice, B. (2006). *Effect of xenon bombardment on ruthenium-coated grazing incidence collector mirror lifetime for extreme ultraviolet lithography*, J. of Appl. Phys., Vol. 100 Issue 5,

*Investigation of ions emitted from a tin fuelled laser produced plasma source*, J. Phys.:

Ruzic, D. N. (2006). *Experimental test chamber design for optics exposure testing and debris characterization of a xenon discharge produced plasma source for extreme ultraviolet lithography*, Microelectronic Engineering, Vol. 83, Iss. 3, pp. 476-484,

*lithography,* Technische Universeit Eindohoven, Proefshcrift, ISBN: 978-90-386-1258-

Kinetic simulation of an extreme ultraviolet radiation driven plasma near a

*etching with hydrogen radicals to clean EUV optics*, Chemical Physics Letters, Vol. 484,

*Origins of debris and mitigation through a secondary RF plasma system for dischargeproduced EUV sources*, Microelectronic Engineering, Vol. 77, Iss. 2, pp. 95-102,


Allain, J.P.; Nieto-Perez, M.; Hendricks, M.R.; Zink, P.; Metzmacher, C.; & Bergmann, K.

Aziz, M. J. (2006). *Nanoscale Morphology Control Using Ion Beams*, Proceeding in Ion Beam

Bakshi, V. Editor (2006). *EUV Sources for Lithography*, SPIE, Bellingham, WA, ISBN

Bakshi, V. Editor (2009). *EUV Lithography*, SPIE and John Wiley & Sons, Hoboken, New

Banine, V. & Moors R. (2004). *Plasma sources for EUV lithography exposure tools*, J. Phys. D:

Banine, V.; Koshelev, K.N.; Swinkels G.H.P.M. (2011) *Physical processes in EUV sources for* 

Benschop, J.; Banine, B.; Lok, S.; & Loopstra, E. (2008). *Extreme ultraviolet lithography: Status* 

Campos, D.; Harilal, S. S.; & Hassanein, A. (2010). *The effect of laser wavelength on emission and particle dynamics of Sn plasma*, J. Appl. Phys. 108, 113305, ISSN 1089-7550 Carter, G., (2001). *The physics and applications of ion beam erosion.* Journal of physics. D,

Chan, W; Chason E (2007). *Making waves: Kinetic processes controlling surface evolution during low energy ion sputtering*, J. Appl. Phys. 101, 121301, DOI:10.1063/1.2749198 Eckstein, W. Comp*uter simulation of ion-solid interactions,* Springer Series in Materials Science,

Fahy, K.; O'Reilly, F.; Scally, E.; & Sheridan, P. (2010). *Robust liquid metal collector mirror for* 

Ghaly, M.; Nordlund, N.; Averback, R.S. (1999). *Molecular dynamics investigations of surface* 

Harilal, S. S.; O'Shay, B.; Tillack, M. S.; Tao, Y.; Paguio, R.; Nikroo, A.; & Back, C. A. (2006).

Hassanein, A.; Sizyuk, V.; and Sizyuk, T. (2008). *Multidimensional simulation and optimization* 

Heinig, K.H.; Muller, T; Schmidt, B; Strobel, M.; Moller, W. (2003). *Interfaces under ion* 

A, vol. 79, Iss. 4, p.795-820, doi: 10.1080/01418619908210332

*EUV and soft x-ray plasma sources*, Proceedings Vol. 7802 in Advances in X-Ray/EUV Optics and Components V, Goto, S.; Khounsary, A. M.; & Morawe, C., Editors (2010). 78020K, 27 August 2010, Proc. SPIE 7802, 78020K (2010);

*damage produced by kiloelectronvolt self-bombardment of solids*, Philosophical Magazine

*Spectral control of emissions from tin doped targets for extreme ultraviolet lithography*, J.

*of hybrid laser and discharge plasma devices for EUV lithography,* Proc. SPIE 6921,

*irradiation: growth and taming of nanostructures,* Appl. Phys. A, vol. 77, iss. 1, pp. 17-

*nm.* Applied Physics A, 100, 1, pp. 231-237, (July 2010), ISSN 0947-8396 Allain, J.P.; Nieto, M.; & Hassanein, A. (2008). *Specular reflectivity of 13.5-nm light from Sn* 

16, (April 2008), ISSN 0947-8396

Jersey, ISBN 978081946949

Appl. Phys. 37 3207

doi:10.1117/12.860747

Phys. D: Appl. Phys. 39 484

25, ISSN: 0947-8396

692113-1-15, DOI:10.1117/12.771218

0819458457

Sigmund, P. (editor), ISBN: 87-7304-330-3

*microlithography*, J. Phys. D: Appl. Phys. 44 253001

*and prospects*, J. Vac. Sci. Technol. B 26, 2204, ISSN 1520-8567

Applied physics 34.3, doi: 10.1088/0022-3727/34/3/201

Vol. 10, Springer, Berlin, 1991, ISBN 3-540-190570-0

(2010). *Energetic Sn+ irradiation effects on ruthenium mirror specular reflectivity at 13.5-*

*islands deposited on grazing incidence mirror surfaces. Applied Physics A*, 91, 1, pp. 13-

Science: Solved and Unsolved Problems, Matematisk-fysiske Meddelelser 52,


**20** 

Keita Sakai *Canon Inc. Japan* 

**High-Index Immersion Lithography** 

The resolution capability of photolithography is given by Rayleigh's equation.

 R=k1·λ/NA , (1) where R is the half-pitch resolution of the image, k1 is a constant that depends on the resist process and exposure method, λ is the exposure wavelength, and NA is the numerical aperture of the projection optic. According to Rayleigh's equation, there are three ways to enhance the resolution. The first is to shorten the exposure wavelength such as extreme ultraviolet lithography (EUVL). The second is to improve the k1 value, for example, using the double-patterning technique. The third is to increase the numerical aperture (NA) as ArF immersion lithography. It has already realized the NA up to 1.35 and moreover can increase the NA using high-index materials. In this chapter, high-index immersion lithography with

The NA is actually determined by the acceptance angle of the lens and the refractive index

 NA=n·sinθ , (2) where n is the refractive index of the medium surrounding the lens and θ is the acceptance angle of the lens. Therefore, the NA can be enlarged by replacing the air (n=1) with a fluid (n>1) as a medium. In this immersion lithography, the film stack consists of a lens, a fluid layer, and a resist layer. The value of n·sinθ is invariant through the film stack because it obeys Snell's Law. Since sinθ is smaller than 1, the maximum NA (=n·sinθ) is limited by the layer with the minimum refractive index. For example, the refractive index of water is 1.44 at 193.4 nm, thus the NA over 1.44 cannot be established as shown in Fig. 1 (a) because of the total reflection. To realize the NA over 1.44, the water must be replaced with a fluid which has a higher refractive index than water (Fig. 1 (b)). In Fig. 1 (b), fused silica has the smallest refractive index in the film stack and it limits the maximum NA. For further increasing the NA, a high-index lens material must be used as

As described above, high-index lens materials and high-index immersion fluids are indispensable to realize high-index immersion lithography. One of the candidates of a highindex lens material is lutetium aluminium garnet (LuAG), which has a refractive index of 2.14. Second-generation (G2) and third-generation (G3) fluids are saturated hydrocarbon

fluids whose refractive indices are approximately 1.64 and 1.80, respectively.

**1. Introduction** 

the NA over 1.45 is focused.

a lens material.

of the medium surrounding the lens and is given by eq. (2).

