Laser lithographic approach to micro-optical freeform elements with extremely large sag heights

doi:10.1364/OE.20.004763

Laser lithographic approach to micro-optical freeform elements with extremely large sag heights

Jens Dunkel, Frank Wippermann, Andreas Brückner, Andreas Bräuer, and Andreas Tünnermann »View Author Affiliations

Optics Express, Vol. 20, Issue 4, pp. 4763-4775 (2012)
http://dx.doi.org/10.1364/OE.20.004763

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Abstract
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Abstract

Artificial compound eye cameras are an attractive approach to generate imaging systems of maximum miniaturization. Their thickness can be reduced by a factor of two in comparison to miniaturized single aperture cameras with the same pixel size and resolution. The imaging performance of these systems can be improved significantly by the use of micro-optical refractive freeform arrays (RFFA). Due to the complexity of these non-symmetric surface profiles with sag heights larger than 50 µm in combination with extreme profile accuracies better than λ/14 (rms), there is no dedicated fabrication technology currently available. In the presented research, significant improvements in the fabrication of these elements with laser lithography were reached. Therefore, a laser lithographic process based on several coating steps in combination with a multiple exposure strategy was developed that is suitable for the fabrication of arbitrary freeform structures with sag heights up to 60 µm. In order to minimize surface deviations caused by unavoidable process nonlinearities, a compensation strategy based on an empirical process model is used. The achievable accuracy of the proposed method and its limitations were investigated by fabricating a spherical micro lens array for demonstration. The fabricated elements possess a shape deviation of less than 1.3 µm (rms) and can be used as master structures for a subsequent replication process in order to realize a cost efficient mass production of artificial compound eye optics on wafer level.

OCIS Codes
(110.0110) Imaging systems : Imaging systems
(220.3740) Optical design and fabrication : Lithography
(220.4000) Optical design and fabrication : Microstructure fabrication
(330.1720) Vision, color, and visual optics : Color vision
(350.3950) Other areas of optics : Micro-optics

ToC Category:
Optical Design and Fabrication

History
Original Manuscript: November 22, 2011
Revised Manuscript: February 3, 2012
Manuscript Accepted: February 3, 2012
Published: February 10, 2012

Virtual Issues
Vol. 7, Iss. 4 Virtual Journal for Biomedical Optics

Citation
Jens Dunkel, Frank Wippermann, Andreas Brückner, Andreas Bräuer, and Andreas Tünnermann, "Laser lithographic approach to micro-optical freeform elements with extremely large sag heights," Opt. Express 20, 4763-4775 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-4-4763

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References

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A. Brueckner, J. Duparré, R. Leitel, P. Dannberg, A. Bräuer, and A. Tünnermann, “Thin wafer-level camera lenses inspired by insect compound eyes,” Opt. Express18(24), 24379–24394 (2010). [CrossRef] [PubMed]
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F. Wippermann, J. Duparré, P. Schreiber, and P. Dannberg, “Design and fabrication of a chirped array of refractive ellipsoidal micro-lenses for an apposition eye camera objective,” Proc. SPIE5962, 59622C, 59622C-11 (2005). [CrossRef]
F. Wippermann, J. Duparré, and P. Schreiber, “Applications of chirped microlens arrays for aberration compensation and improved system integration,” Proc. SPIE6289, 628915, 628915-9 (2006). [CrossRef]
D. Daly, R. F. Stevens, M. C. Hutley, and N. Davies, “The manufacture of microlenses by melting photoresist,” Meas. Sci. Technol.1(8), 759–766 (1990). [CrossRef]
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E. Kley, M. Cumme, L.-C. Wittig, and A. Tünnermann, “Fabrication and properties of refractive micro-optical profiles for lenses, lens arrays and beam shaping elements,” Proc. SPIE4231, 144–152 (2000). [CrossRef]
P. Allen, “Laser scanning for semiconductor mask pattern generation,” in Proceedings of the IEEE, vol.90, no.10, pp. 1653- 1669 (2002).
T. Dresel and J. Schwider, “Fabrication of optical components by laser lithography,” Appl. Surf. Sci.106, 379–382 (1996). [CrossRef]
M. T. Gale, G. K. Lang, T. M. Rayner, and H. Schültz, “Fabrication of micro-optical components by laser beam writing in photoresist,” Proc. SPIE1506, 65–70 (1991). [CrossRef]
D. Radtke and U. D. Zeitner, “Laser-lithography on non-planar surfaces,” Opt. Express15(3), 1167–1174 (2007). [CrossRef] [PubMed]
E. Kley, “Continuous profile writing by electron and optical lithography,” Microelectron. Eng.34(3-4), 261–298 (1997). [CrossRef]
M. T. Gale, M. Rossi, and J. Pedersen, “Fabrication of continuous-relief micro-optical elements by direct laser writing in photoresists,” Opt. Eng.33(11), 3556–3566 (1994). [CrossRef]
T. Hessler, M. Rossi, J. Pedersen, M. T. Gale, M. Wegner, D. Steudle, and H. J. Tiziani, “Microlens arrays with spatial variation of the optical functions,” Pure Appl. Opt.6(6), 673–681 (1997). [CrossRef]
T. Hessler, M. Rossi, R. E. Kunz, and M. T. Gale, “Analysis and optimization of fabrication of continuous-relief diffractive optical elements,” Appl. Opt.37(19), 4069–4079 (1998). [CrossRef] [PubMed]
V. P. Korolkov, R. K. Nasyrov, and R. V. Shimansky, “Optimization for direct laser writing of continuous-relief diffractive optical elements,” Proc. SPIE6732, 6292 (2007).
D. Asselin, P. Topart, L. Sheng, F. Cayer, S. Leclair, and M. Wang, “On-chip replication of high-sag micro-optical components fabricated by direct laser writing,” Proc. SPIE5720, 222–232 (2005). [CrossRef]
T. R. M. Sales, “Structured microlens arrays for beam shaping,” Opt. Eng.42(11), 3084–3085 (2003). [CrossRef]
F. Wippermann, D. Radtke, U. Zeitner, J. W. Duparre, A. Tünnermann, M. Amberg, S. Sinzinger, C. Reinhardt, A. Ovsianikov, and B. N. Chichkov, “Fabrication technologies for chirped refractive microlens arrays,” Proc. SPIE6288, 62880O (2006). [CrossRef]
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V. Kohlmeier, S. Seidemann, Büttgenbach, and H. H. Gatzen, “An investigation on technologies to fabricate microcoils for miniaturized actuator systems,” Microsyst. Technol.10(3), 175–181 (2004).
M. Kubenz, U. Ostrzinski, F. Reuther, and G. Gruetzner, “Effective baking of thick and ultra-thick photoresist layers by infrared radiation,” Microelectron. Eng.67–68, 495–501 (2003). [CrossRef]
M. Cumme, H. Hartung, L. Wittig, and E. B. Kley, “Thick refractive beam shaping elements applied to laser diodes,” Proc. SPIE4440, 25–33 (2001). [CrossRef]
F. Dill, “Optical lithography,” IEEE Trans. Electron. Dev.22(7), 440–444 (1975). [CrossRef]
F. Dill, W. Hornberger, P. Hauge, and J. Shaw, “Characterization of positive photoresist,” IEEE Trans. Electron. Dev.22(7), 445–452 (1975). [CrossRef]
C. Du, X. Dong, C. Qiu, Q. Deng, and C. Zhou, “Profile control technology for high-performance microlens array,” Opt. Eng.43(11), 2595 (2004). [CrossRef]
X. Dong, C. Du, S. Li, C. Wang, and Y. Fu, “Control approach for form accuracy of microlenses with continuous relief,” Opt. Express13(5), 1353–1360 (2005). [CrossRef] [PubMed]
Y. Hirai, K. Inamoto, T. Sugano, Tsuchiya, and O. Tabata, “Moving mask UV lithography for three-dimensional structuring,” J. Micromech. Microeng.17(2), 199–206 (2007). [CrossRef]
K. Hirai, T. Sugano, Tsuchiya, and O. Tabata, “A three-dimensional microstructuring technique exploiting the positive photoresist property,” J. Micromech. Microeng.20(6), 065005 (2010). [CrossRef]
R. E. Jewett, P. I. Hagouel, A. R. Neureuther, and T. van Duzer, “Line-Profile resist development simulation techniques,” Polym. Eng. Sci.17(6), 381–384 (1977). [CrossRef]
K. Toh, A. Neureuther, and E. Scheckler, “Algorithms for simulation of three-dimensional etching,” IEEE Trans. Comput.- Aided Des. Integr. Circuits Syst13(5), 616–624 (1994). [CrossRef]
A. Maréchal, PhD Thesis “Etude des influences conjuguées des aberrations et de la diffraction sur l’image d’unpoint,” Faculté des Sciences de Paris, (1947).

Appl. Opt.

T. Hessler, M. Rossi, R. E. Kunz, and M. T. Gale, “Analysis and optimization of fabrication of continuous-relief diffractive optical elements,” Appl. Opt.37(19), 4069–4079 (1998). [CrossRef] [PubMed]

Appl. Surf. Sci.

T. Dresel and J. Schwider, “Fabrication of optical components by laser lithography,” Appl. Surf. Sci.106, 379–382 (1996). [CrossRef]

IEEE Trans. Comput.- Aided Des. Integr. Circuits Syst

K. Toh, A. Neureuther, and E. Scheckler, “Algorithms for simulation of three-dimensional etching,” IEEE Trans. Comput.- Aided Des. Integr. Circuits Syst13(5), 616–624 (1994). [CrossRef]

IEEE Trans. Electron. Dev.

F. Dill, “Optical lithography,” IEEE Trans. Electron. Dev.22(7), 440–444 (1975). [CrossRef]
F. Dill, W. Hornberger, P. Hauge, and J. Shaw, “Characterization of positive photoresist,” IEEE Trans. Electron. Dev.22(7), 445–452 (1975). [CrossRef]

J. Micromech. Microeng.

Y. Hirai, K. Inamoto, T. Sugano, Tsuchiya, and O. Tabata, “Moving mask UV lithography for three-dimensional structuring,” J. Micromech. Microeng.17(2), 199–206 (2007). [CrossRef]
K. Hirai, T. Sugano, Tsuchiya, and O. Tabata, “A three-dimensional microstructuring technique exploiting the positive photoresist property,” J. Micromech. Microeng.20(6), 065005 (2010). [CrossRef]

Meas. Sci. Technol.

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

Microelectron. Eng.

R. Völkel, M. Eisner, and K. J. Weible, “Miniaturized imaging systems,” Microelectron. Eng.67–68, 461–472 (2003). [CrossRef]
E. Kley, “Continuous profile writing by electron and optical lithography,” Microelectron. Eng.34(3-4), 261–298 (1997). [CrossRef]
M. Kubenz, U. Ostrzinski, F. Reuther, and G. Gruetzner, “Effective baking of thick and ultra-thick photoresist layers by infrared radiation,” Microelectron. Eng.67–68, 495–501 (2003). [CrossRef]

Microsyst. Technol.

V. Kohlmeier, S. Seidemann, Büttgenbach, and H. H. Gatzen, “An investigation on technologies to fabricate microcoils for miniaturized actuator systems,” Microsyst. Technol.10(3), 175–181 (2004).

Opt. Eng.

C. Du, X. Dong, C. Qiu, Q. Deng, and C. Zhou, “Profile control technology for high-performance microlens array,” Opt. Eng.43(11), 2595 (2004). [CrossRef]
M. T. Gale, M. Rossi, and J. Pedersen, “Fabrication of continuous-relief micro-optical elements by direct laser writing in photoresists,” Opt. Eng.33(11), 3556–3566 (1994). [CrossRef]
T. R. M. Sales, “Structured microlens arrays for beam shaping,” Opt. Eng.42(11), 3084–3085 (2003). [CrossRef]

Opt. Express

Polym. Eng. Sci.

R. E. Jewett, P. I. Hagouel, A. R. Neureuther, and T. van Duzer, “Line-Profile resist development simulation techniques,” Polym. Eng. Sci.17(6), 381–384 (1977). [CrossRef]

Proc. SPIE

J. Brown and C. Hamel, “Thick resist for MEMS processing,” Proc. SPIE4592, 334–346 (2001). [CrossRef]
M. Cumme, H. Hartung, L. Wittig, and E. B. Kley, “Thick refractive beam shaping elements applied to laser diodes,” Proc. SPIE4440, 25–33 (2001). [CrossRef]
F. Wippermann, J. Duparré, P. Schreiber, and P. Dannberg, “Design and fabrication of a chirped array of refractive ellipsoidal micro-lenses for an apposition eye camera objective,” Proc. SPIE5962, 59622C, 59622C-11 (2005). [CrossRef]
F. Wippermann, J. Duparré, and P. Schreiber, “Applications of chirped microlens arrays for aberration compensation and improved system integration,” Proc. SPIE6289, 628915, 628915-9 (2006). [CrossRef]
E. Kley, M. Cumme, L.-C. Wittig, and A. Tünnermann, “Fabrication and properties of refractive micro-optical profiles for lenses, lens arrays and beam shaping elements,” Proc. SPIE4231, 144–152 (2000). [CrossRef]
F. Wippermann, D. Radtke, U. Zeitner, J. W. Duparre, A. Tünnermann, M. Amberg, S. Sinzinger, C. Reinhardt, A. Ovsianikov, and B. N. Chichkov, “Fabrication technologies for chirped refractive microlens arrays,” Proc. SPIE6288, 62880O (2006). [CrossRef]
V. P. Korolkov, R. K. Nasyrov, and R. V. Shimansky, “Optimization for direct laser writing of continuous-relief diffractive optical elements,” Proc. SPIE6732, 6292 (2007).
D. Asselin, P. Topart, L. Sheng, F. Cayer, S. Leclair, and M. Wang, “On-chip replication of high-sag micro-optical components fabricated by direct laser writing,” Proc. SPIE5720, 222–232 (2005). [CrossRef]
M. T. Gale, G. K. Lang, T. M. Rayner, and H. Schültz, “Fabrication of micro-optical components by laser beam writing in photoresist,” Proc. SPIE1506, 65–70 (1991). [CrossRef]

Pure Appl. Opt.

T. Hessler, M. Rossi, J. Pedersen, M. T. Gale, M. Wegner, D. Steudle, and H. J. Tiziani, “Microlens arrays with spatial variation of the optical functions,” Pure Appl. Opt.6(6), 673–681 (1997). [CrossRef]

Other

R. Dammel, Diazonaphthoquinone-Based Resists (SPIE Optical Engineering Press, 1993).
P. Allen, “Laser scanning for semiconductor mask pattern generation,” in Proceedings of the IEEE, vol.90, no.10, pp. 1653- 1669 (2002).
S. Scheiding, R. Steinkopf, A. Gebhardt, P. Dannberg, S. Risse, R. Eberhardt, and A. Tünnermann, “Aspheric Lens Array Machining and Replication”, EOS Conference at the World of Photonics Congress 2009 - Session: “High Volume Manufacturing of Optical Components”, 15.-17.6.2009, Munich, Germany Proceedings EOS Conference at the World of Photonics Congress 2009 on CD-ROM.
A. Maréchal, PhD Thesis “Etude des influences conjuguées des aberrations et de la diffraction sur l’image d’unpoint,” Faculté des Sciences de Paris, (1947).

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