Abstract

A new illumination system for mask aligner lithography is presented. The illumination system uses two subsequent microlens-based Köhler integrators. The second Köhler integrator is located in the Fourier plane of the first. The new illumination system uncouples the illumination light from the light source and provides excellent uniformity of the light irradiance and the angular spectrum. Spatial filtering allows to freely shape the angular spectrum to minimize diffraction effects in contact and proximity lithography. Telecentric illumination and ability to precisely control the illumination light allows to introduce resolution enhancement technologies (RET) like customized illumination, optical proximity correction (OPC) and source-mask optimization (SMO) in mask aligner lithography.

© 2010 OSA

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  1. R. Voelkel, U. Vogler, A. Bich, K. J. Weible, M. Eisner, M. Hornung, P. Kaiser, R. Zoberbier, E. Cullmann, „Illumination system for a microlithographic contact and proximity exposure apparatus“, EP 09169158.4, (2009).
  2. U. Vogler, “Optimierung des Beleuchtungssystems für Proximitylithographie in Mask Alignern”, Diploma Thesis, Technische Universität Ilmenau, (2009).
  3. J. Wangler, H. Siekmann, K. J. Weible, R. Scharnweber, M. Deguenther, M. Layh, A. Scholz, U. Spengler, R. Voelkel, „Illumination system for a microlithographic projection exposure apparatus“, EP20070703454, (2007)
  4. A. Köhler, “Zeitschrift für wissenschaftliche,” Mikroskopie X, 433–440 (1893).
  5. J. C. Minano, M. Hernandez, P. Benitez, J. Blen, O. Dross, R. Mohedano, and A. Santamaria, “Free-form integrator array optics”, Proc. SPIE 5942, (2005).
  6. R. Voelkel, and K. J. Weible, “Laser beam homogenizing: limitations and constraints”, Proc. SPIE 7102, (2008)
  7. O. Dross, R. Mohedano, M. Hernández, A. Cvetkovic, P. Benítez, J. Carlos Miñano, “Illumination optics: Köhler integration optics improve illumination homogeneity”, Laser Focus World 45, (2009).
  8. F. M. Dickey, and S. C. Holswade, “Laser Beam Shaping: Theory and Techniques”, Publisher: Marcel Dekker, (2000).
  9. R. Völkel, W. Singer, H. P. Herzig, and R. Dändliker, “Imaging properties of microlens array systems”, MOC'95 Hiroshima, 1995, p. 156–159, The Japan Society of Applied Physics, Tokyo (1995).
  10. K. Räntsch, L. Bertele, H. Sauer, and A. Merz, “Illumination systems”, US Patent 2.186.123, (1938).
  11. In 1963 Karl Süss developed the first Mask Aligner for production of transistors at Siemens in Munich, Germany. Reference: SUSS MicroTec company history, www.suss.com .
  12. Lens arrangement for Köhler integrator was developed in 1978 for mask aligners from Karl SUSS KG, now SUSS MicroTec Lithography GmbH, Garching, Germany, and is referred as “A-Optics”.
  13. D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting a photoresist on a base layer,” Meas. Sci. Technol. 1(8), 759–766 (1990).
    [CrossRef]
  14. S. Haselbeck, H. Schreiber, J. Schwider, and N. Streibl, “Microlenses fabricated by melting photoresist,” Opt. Eng. 32(6), 1322–1324 (1993).
    [CrossRef]
  15. B. Meliorisz, S. Partel, T. Schnattinger, T. Fuhner, A. Erdmann, and P. Hudek, “Investigation of high-resolution contact printing”, Microelectronic Engineering, Volume 85, Issues 5–6, Proceedings of the Micro- and Nano-Engineering 2007 Conference - MNE 2007, May-June 2008, Pages 744–748, ISSN 0167–9317, (2007).
  16. R. Voelkel, H. P. Herzig, Ph. Nussbaum, P. Blattner, R. Dändliker, E. Cullmann, and W. B. Hugle, “Microlens lithography and smart masks,” in Micro-Nano-Engineering 96, Microelectronic Engineering (Elsevier, Amsterdam, 1997).
  17. E. Abbe, “Beiträge zur Theorie des Mikroskops und der Mikroskopischen Wahrnehmung,” Archiv Mikrosc. Anat. 9(1), 413–418 (1873).
    [CrossRef]
  18. T. Harzendorf, L. Stuerzebecher, U. Vogler, U. D. Zeitner, and R. Voelkel, “Half-tone proximity lithography” in Micro-Optics 2010, edited by Hugo Thienpont, Peter Van Daele, Jürgen Mohr, Hans Zappe, Proceedings of SPIE Vol. 7716 (SPIE, Bellingham, WA 2010) 77160Y (2010).
  19. K. Motzek, A. Bich, A. Erdmann, M. Hornung, M. Hennemeyer, B. Meliorisz, U. Hofmann, N. Unal, R. Voelkel, S. Partel, and P. Hudek, “Optimization of illumination pupils and mask structures for proximity printing”, Microelectronic Engineering, Volume 87, Issues 5–8, The 35th International Conference on Micro- and Nano-Engineering (MNE), May-August 2010, Pages 1164–1167, ISSN 0167–9317 (2010).
  20. L. Stuerzebecher, T. Harzendorf, U. Vogler, U. Zeitner, and R. Voelkel, “Advanced mask aligner lithography: fabrication of periodic patterns using pinhole array mask and Talbot effect,” Opt. Express 18(19), 19485–19494 (2010).
    [CrossRef] [PubMed]

2010 (1)

1993 (1)

S. Haselbeck, H. Schreiber, J. Schwider, and N. Streibl, “Microlenses fabricated by melting photoresist,” Opt. Eng. 32(6), 1322–1324 (1993).
[CrossRef]

1990 (1)

D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting a photoresist on a base layer,” Meas. Sci. Technol. 1(8), 759–766 (1990).
[CrossRef]

1893 (1)

A. Köhler, “Zeitschrift für wissenschaftliche,” Mikroskopie X, 433–440 (1893).

1873 (1)

E. Abbe, “Beiträge zur Theorie des Mikroskops und der Mikroskopischen Wahrnehmung,” Archiv Mikrosc. Anat. 9(1), 413–418 (1873).
[CrossRef]

Abbe, E.

E. Abbe, “Beiträge zur Theorie des Mikroskops und der Mikroskopischen Wahrnehmung,” Archiv Mikrosc. Anat. 9(1), 413–418 (1873).
[CrossRef]

Daly, D.

D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting a photoresist on a base layer,” Meas. Sci. Technol. 1(8), 759–766 (1990).
[CrossRef]

Davies, N.

D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting a photoresist on a base layer,” Meas. Sci. Technol. 1(8), 759–766 (1990).
[CrossRef]

Harzendorf, T.

Haselbeck, S.

S. Haselbeck, H. Schreiber, J. Schwider, and N. Streibl, “Microlenses fabricated by melting photoresist,” Opt. Eng. 32(6), 1322–1324 (1993).
[CrossRef]

Hutley, M. C.

D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting a photoresist on a base layer,” Meas. Sci. Technol. 1(8), 759–766 (1990).
[CrossRef]

Köhler, A.

A. Köhler, “Zeitschrift für wissenschaftliche,” Mikroskopie X, 433–440 (1893).

Schreiber, H.

S. Haselbeck, H. Schreiber, J. Schwider, and N. Streibl, “Microlenses fabricated by melting photoresist,” Opt. Eng. 32(6), 1322–1324 (1993).
[CrossRef]

Schwider, J.

S. Haselbeck, H. Schreiber, J. Schwider, and N. Streibl, “Microlenses fabricated by melting photoresist,” Opt. Eng. 32(6), 1322–1324 (1993).
[CrossRef]

Stevens, R. F.

D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting a photoresist on a base layer,” Meas. Sci. Technol. 1(8), 759–766 (1990).
[CrossRef]

Streibl, N.

S. Haselbeck, H. Schreiber, J. Schwider, and N. Streibl, “Microlenses fabricated by melting photoresist,” Opt. Eng. 32(6), 1322–1324 (1993).
[CrossRef]

Stuerzebecher, L.

Voelkel, R.

Vogler, U.

Zeitner, U.

Archiv Mikrosc. Anat. (1)

E. Abbe, “Beiträge zur Theorie des Mikroskops und der Mikroskopischen Wahrnehmung,” Archiv Mikrosc. Anat. 9(1), 413–418 (1873).
[CrossRef]

Meas. Sci. Technol. (1)

D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting a photoresist on a base layer,” Meas. Sci. Technol. 1(8), 759–766 (1990).
[CrossRef]

Mikroskopie (1)

A. Köhler, “Zeitschrift für wissenschaftliche,” Mikroskopie X, 433–440 (1893).

Opt. Eng. (1)

S. Haselbeck, H. Schreiber, J. Schwider, and N. Streibl, “Microlenses fabricated by melting photoresist,” Opt. Eng. 32(6), 1322–1324 (1993).
[CrossRef]

Opt. Express (1)

Other (15)

B. Meliorisz, S. Partel, T. Schnattinger, T. Fuhner, A. Erdmann, and P. Hudek, “Investigation of high-resolution contact printing”, Microelectronic Engineering, Volume 85, Issues 5–6, Proceedings of the Micro- and Nano-Engineering 2007 Conference - MNE 2007, May-June 2008, Pages 744–748, ISSN 0167–9317, (2007).

R. Voelkel, H. P. Herzig, Ph. Nussbaum, P. Blattner, R. Dändliker, E. Cullmann, and W. B. Hugle, “Microlens lithography and smart masks,” in Micro-Nano-Engineering 96, Microelectronic Engineering (Elsevier, Amsterdam, 1997).

T. Harzendorf, L. Stuerzebecher, U. Vogler, U. D. Zeitner, and R. Voelkel, “Half-tone proximity lithography” in Micro-Optics 2010, edited by Hugo Thienpont, Peter Van Daele, Jürgen Mohr, Hans Zappe, Proceedings of SPIE Vol. 7716 (SPIE, Bellingham, WA 2010) 77160Y (2010).

K. Motzek, A. Bich, A. Erdmann, M. Hornung, M. Hennemeyer, B. Meliorisz, U. Hofmann, N. Unal, R. Voelkel, S. Partel, and P. Hudek, “Optimization of illumination pupils and mask structures for proximity printing”, Microelectronic Engineering, Volume 87, Issues 5–8, The 35th International Conference on Micro- and Nano-Engineering (MNE), May-August 2010, Pages 1164–1167, ISSN 0167–9317 (2010).

R. Voelkel, U. Vogler, A. Bich, K. J. Weible, M. Eisner, M. Hornung, P. Kaiser, R. Zoberbier, E. Cullmann, „Illumination system for a microlithographic contact and proximity exposure apparatus“, EP 09169158.4, (2009).

U. Vogler, “Optimierung des Beleuchtungssystems für Proximitylithographie in Mask Alignern”, Diploma Thesis, Technische Universität Ilmenau, (2009).

J. Wangler, H. Siekmann, K. J. Weible, R. Scharnweber, M. Deguenther, M. Layh, A. Scholz, U. Spengler, R. Voelkel, „Illumination system for a microlithographic projection exposure apparatus“, EP20070703454, (2007)

J. C. Minano, M. Hernandez, P. Benitez, J. Blen, O. Dross, R. Mohedano, and A. Santamaria, “Free-form integrator array optics”, Proc. SPIE 5942, (2005).

R. Voelkel, and K. J. Weible, “Laser beam homogenizing: limitations and constraints”, Proc. SPIE 7102, (2008)

O. Dross, R. Mohedano, M. Hernández, A. Cvetkovic, P. Benítez, J. Carlos Miñano, “Illumination optics: Köhler integration optics improve illumination homogeneity”, Laser Focus World 45, (2009).

F. M. Dickey, and S. C. Holswade, “Laser Beam Shaping: Theory and Techniques”, Publisher: Marcel Dekker, (2000).

R. Völkel, W. Singer, H. P. Herzig, and R. Dändliker, “Imaging properties of microlens array systems”, MOC'95 Hiroshima, 1995, p. 156–159, The Japan Society of Applied Physics, Tokyo (1995).

K. Räntsch, L. Bertele, H. Sauer, and A. Merz, “Illumination systems”, US Patent 2.186.123, (1938).

In 1963 Karl Süss developed the first Mask Aligner for production of transistors at Siemens in Munich, Germany. Reference: SUSS MicroTec company history, www.suss.com .

Lens arrangement for Köhler integrator was developed in 1978 for mask aligners from Karl SUSS KG, now SUSS MicroTec Lithography GmbH, Garching, Germany, and is referred as “A-Optics”.

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Figures (11)

Fig. 1
Fig. 1

Scheme of an ellipsoidal reflector as used for Mask aligner illumination.

Fig. 2
Fig. 2

Scheme of a Köhler integrator collecting light from an extended light source within an integration zone and providing uniform irradiance in the Fourier plane of the Fourier lens. Two symmetrical lens arrays located at a focal length distance (f1 = f2) are used for light mixing. The aperture splitting of the lens array provides a plurality of parallel Köhler illumination systems perfectly decoupling illumination in the Fourier plane from the light source.

Fig. 3
Fig. 3

(a) Schematic view of a standard illumination system for mask aligner lithography comprising an ellipsoidal reflector, 2 optical integrators, a condenser and a front lens. (b) First optical integrator: An array of pyramids used in secondary focus of ellipsoid reflector to redistribute the light. (c) Second optical integrator: Lens array comprising single lenses mounted in multi-aperture metal holder as used for Köhler integration (Fig. 2).

Fig. 4
Fig. 4

Simplified view of a mask aligner illumination system comprising two subsequent Köhler integrators. A first Köhler integrator is located near the secondary focal point of the ellipsoidal reflector. A second Köhler integrator is located in the Fourier plane of the first integrator.

Fig. 5
Fig. 5

(a) Flat-top irradiance distribution in the far-field of a microlens array manufactured in Fused Silica by resist melting and reactive ion etching technology measured in a goniometer. (b) Schematic drawings of the microlens arrays used as Köhler integrator elements.

Fig. 6
Fig. 6

Illumination of photomask with (a) non-telecentric and (b) telecentric light. Telecentricity error of mask illumination light bundle leads to lateral displacement errors also referred as “run-out errors” of the printing pattern on the wafer for shadow lithography in mask aligner using proximity mode.

Fig. 7
Fig. 7

(a) Köhler integrator with a large-area microlens arrays as used in the new illumination system. (b) Metal mask used as exchangeable illumination filter plate (IFP) providing a similar angular spectrum of mask illuminating light than the standard “A-Optics” mask aligner illumination shown in Fig. 3. (c) The illumination filter plate is placed in front of the first microlens array of the second Köhler integrator.

Fig. 8
Fig. 8

Angular spectrum of the illumination light impinging the photomask for (a) standard mask aligner illumination system (Fig. 3) in the mask center, (b) at the mask rim. (c) Angular spectrum using the new illumination system (Fig. 4) and an identical spatial filter configuration (Fig. 7), observed at the mask rim. The angular spectrum expressed in color graduation (arbitray units) was measured by recording the Fourier image of a single lens located in the mask plane.

Fig. 9
Fig. 9

Simplified lithography model for the use of the new illumination system in proximity lithography. (a) For a single opening in the mask the illumination filter pattern is imaged to the wafer plane. (b) The illumination filter plane is assumed to be subdivided in a multitude of coherent areas, where each is considered to be an ideal coherent source, but no coherence between different areas is assumed. The geometry of the illumination filter plate defines which of the coherent areas are transmitted and can contribute to the mask illumination.

Fig. 10
Fig. 10

Experimental results for mask aligner lithography using the new illumination system and customized illumination. Photographs of (a) of 10 x 10 microns squares holes with 10 microns pitch on a photomask and (b) to (d) the resulting prints in 1.2 micron thick photoresist exposed at a proximity gap of 100 microns behind the photomask using different illumination filters.

Fig. 11
Fig. 11

Experimental results for mask aligner lithography using the new illumination system, customized illumination and optical proximity correction (OPC). Photographs of resist prints (AZ 4110, 1.2 micron thick) obtained for a proximity gap of 50 microns. The resist image in the upper left corner shows the print result for a 10 x 10 microns square, similar to Fig. 10 (a), illuminated with a circular illumination filter and no OPC correction. The influence of OPC assist features (serifs) of different size (columns) and at a different position (row) are shown in a matrix.

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