Abstract

Immersion interference lithography was used to pattern gratings with 22-nm half pitch. This ultrahigh resolution was made possible by using 157-nm light, a sapphire coupling prism with index 2.09, and a 30-nm-thick immersion fluid with index 1.82. The thickness was controlled precisely by spin-casting the fluid rather than through mechanical means. The photoresist was a diluted version of a 193-nm material, which had a 157-nm index of 1.74. An analysis of the trade-off between fluid index, absorption coefficient, gap size and throughput indicated that, among the currently available materials, employing a high-index but absorbing fluid is preferable to using a highly transparent but low-index immersion media.

© 2006 Optical Society of America

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References

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  1. B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).
  2. H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
    [CrossRef]
  3. M. Switkes and M. Rothschild, "Immersion lithography at 157 nm," J. Vac. Sci. Technol. B 19, 2353 (2001).
    [CrossRef]
  4. M. Switkes, T. M. Bloomstein, and M. Rothschild, "Patterning of sub-50 nm dense features with space-invariant 157 nm interference lithography," Appl. Phys. Lett. 20,3149 (2000).
    [CrossRef]
  5. W. J. Tropf and M. E. Thomas, "Aluminum Oxide (Al2O3) Revisited," in Handbook of Optical Constants of Solids III, E. D. Palik, ed. (Academic Press, New York, 1998) pp. 653-682.
  6. M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
    [CrossRef]
  7. P. H. Berning, "Theory and Calculations of Optical Thin Films," in Physics of Thin Films, G. Hass, ed. (Academic Press, New York, 1963), Vol. 1, pp. 69-121.

2006 (2)

B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

2004 (1)

M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
[CrossRef]

2001 (1)

M. Switkes and M. Rothschild, "Immersion lithography at 157 nm," J. Vac. Sci. Technol. B 19, 2353 (2001).
[CrossRef]

2000 (1)

M. Switkes, T. M. Bloomstein, and M. Rothschild, "Patterning of sub-50 nm dense features with space-invariant 157 nm interference lithography," Appl. Phys. Lett. 20,3149 (2000).
[CrossRef]

Bloomstein, T. M.

M. Switkes, T. M. Bloomstein, and M. Rothschild, "Patterning of sub-50 nm dense features with space-invariant 157 nm interference lithography," Appl. Phys. Lett. 20,3149 (2000).
[CrossRef]

Bonnecaze, R. T.

M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
[CrossRef]

Choi, B. J.

M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
[CrossRef]

Colburn, M.

M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
[CrossRef]

Estroff, A.

B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).

Fan, Y.

B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).

Gräupner, P.

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

Lafferty, N.

B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).

Markoya, L.

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

McCafferty, D.

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

Mulkens, J.

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

Rothschild, M.

M. Switkes and M. Rothschild, "Immersion lithography at 157 nm," J. Vac. Sci. Technol. B 19, 2353 (2001).
[CrossRef]

M. Switkes, T. M. Bloomstein, and M. Rothschild, "Patterning of sub-50 nm dense features with space-invariant 157 nm interference lithography," Appl. Phys. Lett. 20,3149 (2000).
[CrossRef]

Sewell, H.

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

Smith, B. W.

B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).

Sreenivasan, S. V.

M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
[CrossRef]

Streefkerk, B.

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

Switkes, M.

M. Switkes and M. Rothschild, "Immersion lithography at 157 nm," J. Vac. Sci. Technol. B 19, 2353 (2001).
[CrossRef]

M. Switkes, T. M. Bloomstein, and M. Rothschild, "Patterning of sub-50 nm dense features with space-invariant 157 nm interference lithography," Appl. Phys. Lett. 20,3149 (2000).
[CrossRef]

Willson, C. G.

M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
[CrossRef]

Zhou, J.

B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).

Appl. Phys. Lett. (1)

M. Switkes, T. M. Bloomstein, and M. Rothschild, "Patterning of sub-50 nm dense features with space-invariant 157 nm interference lithography," Appl. Phys. Lett. 20,3149 (2000).
[CrossRef]

J. Vac. Sci. Technol. B (1)

M. Switkes and M. Rothschild, "Immersion lithography at 157 nm," J. Vac. Sci. Technol. B 19, 2353 (2001).
[CrossRef]

Micro. Eng. (1)

M. Colburn, B. J. Choi, S. V. Sreenivasan, R. T. Bonnecaze, and C. G. Willson, "Ramifications of lubrication theory on imprint lithography," Micro. Eng. 75, 321-329 (2004).
[CrossRef]

Proc. SPIE (2)

B. W. Smith, Y. Fan, J. Zhou, N. Lafferty, and A. Estroff, "Evanescent wave imaging in optical lithography," Proc. SPIE 6154 (2006) (to be published).

H. Sewell, J. Mulkens, D. McCafferty, L. Markoya, B. Streefkerk, and P. Gräupner, "The next phase for immersion lithography," Proc. SPIE 6154 (2006) (to be published).
[CrossRef]

Other (2)

W. J. Tropf and M. E. Thomas, "Aluminum Oxide (Al2O3) Revisited," in Handbook of Optical Constants of Solids III, E. D. Palik, ed. (Academic Press, New York, 1998) pp. 653-682.

P. H. Berning, "Theory and Calculations of Optical Thin Films," in Physics of Thin Films, G. Hass, ed. (Academic Press, New York, 1963), Vol. 1, pp. 69-121.

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Figures (5)

Fig. 1.
Fig. 1.

Schematic representation of the output portion of the interference system. The input beams are transverse electric (TE) polarized.

Fig. 2.
Fig. 2.

Transmission of a 6.35-mm-thick VUV grade sapphire window measured in an Acton Research Corp. vacuum ultraviolet spectrometer purged with nitrogen. The transmission is 43% at 157.6 nm.

Fig. 3.
Fig. 3.

SEM of patterned photoresist using interference lithography with a 30-nm-thick high-index absorptive immersion liquid. The pitch is 44 nm, as expected from the index of the sapphire prism, the laser wavelength and the angle of incidence of the interfering beams. The total exposure dose is 48 mJ/cm2.

Fig. 4.
Fig. 4.

Schematic representation of electric field vectors in the multilayer system under consideration.

Fig. 5.
Fig. 5.

(a) Coupling efficiency into resist as a function of liquid layer thickness using a sapphire coupling prism with index of 2.09, interfering beams intersecting at 60°, and vacuum wavelength of 157.6 nm. (b) Coupling efficiency into the photoresist for a 30-nm gap for several immersion fluids.

Tables (1)

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Table 1. Liquid Properties and Pressure Conditions

Equations (16)

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h f h o = 1 1 + t τ
τ = 3 μ R 2 16 P gauge h o 2
E i = E i e j ( k x x + k zp z ) i ̂ y + E i e j ( k x x + k zp z ) i ̂ y
= 2 E i cos ( k x x ) e j k zp z i ̂ y
E r p = 2 E r p cos ( k x x ) e j k z p z i ̂ y
E tliq = 2 E tliq cos ( k x x ) e j k zliq z i ̂ y
E rliq = 2 E rliq cos ( k x x ) e j k zliq z i ̂ y
E tr = 2 E tr cos ( k x x ) e j k zr z i ̂ y
k x = k i sin θ = ( 2 π λ ) n p sin θ
k zp = ( 2 π λ ) n p cos θ
k zliq = 2 π λ ( n liq 2 n p 2 sin 2 θ κ liq 2 ) j 2 n liq κ liq
k zr = 2 π λ ( n r 2 n p 2 sin 2 θ κ r 2 ) j 2 n r κ r
S tr = T 2 Re [ k zr * ] Re [ k zp * ] cos 2 ( k x x ) e ( 2 Im [ k zr ] ) z i ̂ z
T = 2 ( 1 + k zliq k zr k zliq + k zr ) e j k zliq t liq ( 1 + k zliq k zr k zliq + k zr e 2 j k zliq t liq ) + k zliq k zp ( 1 k zliq k zr k zliq + k zr e 2 j k zliq t liq )
Λ = ( λ 2 ) ( n p sin θ )
sin θ cr = n liq n p = 1 n p

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