Abstract

This paper successfully used inclined exposure technology to fabricate 45° polymer optical grade micromirrors (1.4mm thick) while applying the surface free energy minimization principle to improve sidewall indentation. This paper tests the effect of the reflow process on the surface roughness of inclined surfaces. Experimental results are considered in light of the theory of minimizing free energy. The smallest surface roughness achieved in the experiments using SU-8 material with a thickness of 1.4mm was less than 20nm. The effect of the reflow process on the surface indentation of inclined microstructures showed that the 1D WYKO profile of maximum height fell from 0.81μm to 0.08μm (Rt), which is an improvement of 90% after the reflow process. This type of micromirror can be used as a key component in Blu-Ray optical pickup heads used in portable, high-density storage systems.

© 2009 Optical Society of America

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  1. Y. J. Chuang, F. G. Tseng, J. H. Cheng, and W. K. Lin, “A novel fabrication method of embedded micro-channels by using SU-8 thick-film photoresists,” Sens. Actuators A Phys. 103, 64-69 (2003).
    [CrossRef]
  2. K. Y. Hung, F. G. Tseng, and H. P. Chou, “Application of 3D gray mask for the fabrication of curved SU-8 structures,” J. Microsyst. Technol. 11, 365-369 (2005).
    [CrossRef]
  3. M. Lindblom, H. M. Hertz, and A. Holmberg, “SU-8 plating mold for high-aspect-ratio nickel zone plates,” J. Microelectron. Eng. 84, 1136-1139 (2007).
    [CrossRef]
  4. K. Y. Hung and T. H. Liang, “Application of inclined-exposure and thick film process for high aspect-ratio micro structures on polymer optic devices,” J. Microsyst. Technol. 14, 1217-1222 (2008).
    [CrossRef]
  5. K. Y. Hung, H. T. Hu, and F. G. Tseng, “Application 3D glycerol-compensated inclined-exposure technology to integrated optical pick-up head,” J. Micromech. Microeng. 14, 975-83 (2004).
    [CrossRef]
  6. C. H. Lee, K. Jiang, and G. J. Davies, “Sidewall roughness characterization and comparison between silicon and SU-8 microcomponents,” Mater. Char. 58, 603-609 (2007).
    [CrossRef]
  7. Y. K. Yoon, J. H. Park, and M. G. Allen, “Multidirectional UV lithography for complex 3-D MEMS structures,” J. Microelectromech. Syst. 15, 1121-1130 (2006).
    [CrossRef]
  8. C. Strandman, “Fabrication of 45 mirrors together with well-defined V-grooves using wet anisotropic etching of silicon,” J. Microelectromech. Syst. 4, 213-219 (1995).
    [CrossRef]
  9. O. Powell and H. B. Harrison, “Anisotropic etching of {100} and {110} planes in (100) silicon,” J. Micromech. Microeng. 11, 217-220 (2001).
    [CrossRef]
  10. K. D. Vora, B. Y. Shew, E. C. Harvey, J. P. Hayes, and A. G. Peele, “Sidewall slopes of SU-8 HARMST using deep x-ray lithography,” J. Micromech. Microeng. 18, 035037 (2008).
    [CrossRef]
  11. K. D. Vora, B. Lochel, E. C. Harvey, J. P. Hayes, and A. G. Peele, “AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography,” J. Micromech. Microeng. 16, 1975-1983 (2006).
    [CrossRef]
  12. E. Rabe, S. Kopetz, and A. Neyer, “The generation of mould patterns for multimode optical waveguide components by direct laser writing of SU-8 at 364 nm,” J. Micromech. Microeng. 17, 1664-1670 (2007).
    [CrossRef]
  13. R. Yang and W. J. Wang, “A numerical and experimental study on gap compensation and wavelength selection in UV-lithography of ultra-high aspect ratio SU-8 microstructures,” Sens. Actuators B Chem. 110, 279-288 (2005).
    [CrossRef]
  14. E. F. Reznikova, J. Mohr, and H. Hein, “Deep photo-lithography characterization of SU-8 resist layers,” J. Microsyst. Technol. 11, 282-291 (2005).
    [CrossRef]
  15. W. J. Kang, E. Rabe, S. Kopetz, and A. Neyer, “Novel exposure methods based on reflection and refraction effects in the field of SU-8 lithography,” J. Micromech. Microeng. 16, 821-831(2006).
    [CrossRef]
  16. K. Y. Hung and J. C. Liao, “The application of Fresnel equations and anti-reflection technology to improve inclined exposure interface reflection and develop a key component needed for blu-ray dvd--micro-mirrors,” J. Micromech. Microeng. 18, 075022 (2008).
    [CrossRef]
  17. Y. J. Chuang, F. G. Tseng, and W. K. Lin “Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination,” J. Microsyst. Technol. 8, 308-313(2002).
    [CrossRef]
  18. W. W. Mullins, “Theory of thermal grooving,” J. Appl. Physi. 28, 333-339 (1957).
    [CrossRef]
  19. W. W. Mullins, “Flattening of a nearly plane solid surface due to capillarity,” J. Appl. Physi. 30, 77-83 (1959).
    [CrossRef]
  20. L. J. Friedrich, S. K. Dew, M. J. Brett, and T. Smy, “A simulation study of copper reflow characteristics in vias,” IEEE Trans. Semicond. Manuf. 12, 353-365 (1999).
    [CrossRef]
  21. C. Herring, “Surface tension as a motivation for sintering,” Physics of Powder Metallurgy (McGraw-Hill, 1951), pp. 143-179.
  22. H. F. Shih, G. D. Lin, C. S. Lu, Y. C. Lee, Y. Chiu, and K. Y. Hung, “Micro objective lens and optical pickup head design for the blue-light small form factor storage system,” in Technical Digest of 6th International Conference on Optics-Photonics Design & Fabrication (Optical Society of Japan, 2008), pp. 9-11.
  23. Partially based on the following paper presented at μTAS 2009 Conference: K. Y. Hung, et al., “Application of the surface free energy minimization principle to improve sidewall indentation of polymer inclined mirrors,” The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences (μTAS 2009), Jeju Island, Korea, 1-5 November, 2009.

2008

K. Y. Hung and T. H. Liang, “Application of inclined-exposure and thick film process for high aspect-ratio micro structures on polymer optic devices,” J. Microsyst. Technol. 14, 1217-1222 (2008).
[CrossRef]

K. D. Vora, B. Y. Shew, E. C. Harvey, J. P. Hayes, and A. G. Peele, “Sidewall slopes of SU-8 HARMST using deep x-ray lithography,” J. Micromech. Microeng. 18, 035037 (2008).
[CrossRef]

K. Y. Hung and J. C. Liao, “The application of Fresnel equations and anti-reflection technology to improve inclined exposure interface reflection and develop a key component needed for blu-ray dvd--micro-mirrors,” J. Micromech. Microeng. 18, 075022 (2008).
[CrossRef]

2007

E. Rabe, S. Kopetz, and A. Neyer, “The generation of mould patterns for multimode optical waveguide components by direct laser writing of SU-8 at 364 nm,” J. Micromech. Microeng. 17, 1664-1670 (2007).
[CrossRef]

C. H. Lee, K. Jiang, and G. J. Davies, “Sidewall roughness characterization and comparison between silicon and SU-8 microcomponents,” Mater. Char. 58, 603-609 (2007).
[CrossRef]

M. Lindblom, H. M. Hertz, and A. Holmberg, “SU-8 plating mold for high-aspect-ratio nickel zone plates,” J. Microelectron. Eng. 84, 1136-1139 (2007).
[CrossRef]

2006

Y. K. Yoon, J. H. Park, and M. G. Allen, “Multidirectional UV lithography for complex 3-D MEMS structures,” J. Microelectromech. Syst. 15, 1121-1130 (2006).
[CrossRef]

K. D. Vora, B. Lochel, E. C. Harvey, J. P. Hayes, and A. G. Peele, “AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography,” J. Micromech. Microeng. 16, 1975-1983 (2006).
[CrossRef]

W. J. Kang, E. Rabe, S. Kopetz, and A. Neyer, “Novel exposure methods based on reflection and refraction effects in the field of SU-8 lithography,” J. Micromech. Microeng. 16, 821-831(2006).
[CrossRef]

2005

R. Yang and W. J. Wang, “A numerical and experimental study on gap compensation and wavelength selection in UV-lithography of ultra-high aspect ratio SU-8 microstructures,” Sens. Actuators B Chem. 110, 279-288 (2005).
[CrossRef]

E. F. Reznikova, J. Mohr, and H. Hein, “Deep photo-lithography characterization of SU-8 resist layers,” J. Microsyst. Technol. 11, 282-291 (2005).
[CrossRef]

K. Y. Hung, F. G. Tseng, and H. P. Chou, “Application of 3D gray mask for the fabrication of curved SU-8 structures,” J. Microsyst. Technol. 11, 365-369 (2005).
[CrossRef]

2004

K. Y. Hung, H. T. Hu, and F. G. Tseng, “Application 3D glycerol-compensated inclined-exposure technology to integrated optical pick-up head,” J. Micromech. Microeng. 14, 975-83 (2004).
[CrossRef]

2003

Y. J. Chuang, F. G. Tseng, J. H. Cheng, and W. K. Lin, “A novel fabrication method of embedded micro-channels by using SU-8 thick-film photoresists,” Sens. Actuators A Phys. 103, 64-69 (2003).
[CrossRef]

2002

Y. J. Chuang, F. G. Tseng, and W. K. Lin “Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination,” J. Microsyst. Technol. 8, 308-313(2002).
[CrossRef]

2001

O. Powell and H. B. Harrison, “Anisotropic etching of {100} and {110} planes in (100) silicon,” J. Micromech. Microeng. 11, 217-220 (2001).
[CrossRef]

1999

L. J. Friedrich, S. K. Dew, M. J. Brett, and T. Smy, “A simulation study of copper reflow characteristics in vias,” IEEE Trans. Semicond. Manuf. 12, 353-365 (1999).
[CrossRef]

1995

C. Strandman, “Fabrication of 45 mirrors together with well-defined V-grooves using wet anisotropic etching of silicon,” J. Microelectromech. Syst. 4, 213-219 (1995).
[CrossRef]

1959

W. W. Mullins, “Flattening of a nearly plane solid surface due to capillarity,” J. Appl. Physi. 30, 77-83 (1959).
[CrossRef]

1957

W. W. Mullins, “Theory of thermal grooving,” J. Appl. Physi. 28, 333-339 (1957).
[CrossRef]

Allen, M. G.

Y. K. Yoon, J. H. Park, and M. G. Allen, “Multidirectional UV lithography for complex 3-D MEMS structures,” J. Microelectromech. Syst. 15, 1121-1130 (2006).
[CrossRef]

Brett, M. J.

L. J. Friedrich, S. K. Dew, M. J. Brett, and T. Smy, “A simulation study of copper reflow characteristics in vias,” IEEE Trans. Semicond. Manuf. 12, 353-365 (1999).
[CrossRef]

Cheng, J. H.

Y. J. Chuang, F. G. Tseng, J. H. Cheng, and W. K. Lin, “A novel fabrication method of embedded micro-channels by using SU-8 thick-film photoresists,” Sens. Actuators A Phys. 103, 64-69 (2003).
[CrossRef]

Chiu, Y.

H. F. Shih, G. D. Lin, C. S. Lu, Y. C. Lee, Y. Chiu, and K. Y. Hung, “Micro objective lens and optical pickup head design for the blue-light small form factor storage system,” in Technical Digest of 6th International Conference on Optics-Photonics Design & Fabrication (Optical Society of Japan, 2008), pp. 9-11.

Chou, H. P.

K. Y. Hung, F. G. Tseng, and H. P. Chou, “Application of 3D gray mask for the fabrication of curved SU-8 structures,” J. Microsyst. Technol. 11, 365-369 (2005).
[CrossRef]

Chuang, Y. J.

Y. J. Chuang, F. G. Tseng, J. H. Cheng, and W. K. Lin, “A novel fabrication method of embedded micro-channels by using SU-8 thick-film photoresists,” Sens. Actuators A Phys. 103, 64-69 (2003).
[CrossRef]

Y. J. Chuang, F. G. Tseng, and W. K. Lin “Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination,” J. Microsyst. Technol. 8, 308-313(2002).
[CrossRef]

Davies, G. J.

C. H. Lee, K. Jiang, and G. J. Davies, “Sidewall roughness characterization and comparison between silicon and SU-8 microcomponents,” Mater. Char. 58, 603-609 (2007).
[CrossRef]

Dew, S. K.

L. J. Friedrich, S. K. Dew, M. J. Brett, and T. Smy, “A simulation study of copper reflow characteristics in vias,” IEEE Trans. Semicond. Manuf. 12, 353-365 (1999).
[CrossRef]

Friedrich, L. J.

L. J. Friedrich, S. K. Dew, M. J. Brett, and T. Smy, “A simulation study of copper reflow characteristics in vias,” IEEE Trans. Semicond. Manuf. 12, 353-365 (1999).
[CrossRef]

Harrison, H. B.

O. Powell and H. B. Harrison, “Anisotropic etching of {100} and {110} planes in (100) silicon,” J. Micromech. Microeng. 11, 217-220 (2001).
[CrossRef]

Harvey, E. C.

K. D. Vora, B. Y. Shew, E. C. Harvey, J. P. Hayes, and A. G. Peele, “Sidewall slopes of SU-8 HARMST using deep x-ray lithography,” J. Micromech. Microeng. 18, 035037 (2008).
[CrossRef]

K. D. Vora, B. Lochel, E. C. Harvey, J. P. Hayes, and A. G. Peele, “AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography,” J. Micromech. Microeng. 16, 1975-1983 (2006).
[CrossRef]

Hayes, J. P.

K. D. Vora, B. Y. Shew, E. C. Harvey, J. P. Hayes, and A. G. Peele, “Sidewall slopes of SU-8 HARMST using deep x-ray lithography,” J. Micromech. Microeng. 18, 035037 (2008).
[CrossRef]

K. D. Vora, B. Lochel, E. C. Harvey, J. P. Hayes, and A. G. Peele, “AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography,” J. Micromech. Microeng. 16, 1975-1983 (2006).
[CrossRef]

Hein, H.

E. F. Reznikova, J. Mohr, and H. Hein, “Deep photo-lithography characterization of SU-8 resist layers,” J. Microsyst. Technol. 11, 282-291 (2005).
[CrossRef]

Herring, C.

C. Herring, “Surface tension as a motivation for sintering,” Physics of Powder Metallurgy (McGraw-Hill, 1951), pp. 143-179.

Hertz, H. M.

M. Lindblom, H. M. Hertz, and A. Holmberg, “SU-8 plating mold for high-aspect-ratio nickel zone plates,” J. Microelectron. Eng. 84, 1136-1139 (2007).
[CrossRef]

Holmberg, A.

M. Lindblom, H. M. Hertz, and A. Holmberg, “SU-8 plating mold for high-aspect-ratio nickel zone plates,” J. Microelectron. Eng. 84, 1136-1139 (2007).
[CrossRef]

Hu, H. T.

K. Y. Hung, H. T. Hu, and F. G. Tseng, “Application 3D glycerol-compensated inclined-exposure technology to integrated optical pick-up head,” J. Micromech. Microeng. 14, 975-83 (2004).
[CrossRef]

Hung, K. Y.

K. Y. Hung and T. H. Liang, “Application of inclined-exposure and thick film process for high aspect-ratio micro structures on polymer optic devices,” J. Microsyst. Technol. 14, 1217-1222 (2008).
[CrossRef]

K. Y. Hung and J. C. Liao, “The application of Fresnel equations and anti-reflection technology to improve inclined exposure interface reflection and develop a key component needed for blu-ray dvd--micro-mirrors,” J. Micromech. Microeng. 18, 075022 (2008).
[CrossRef]

K. Y. Hung, F. G. Tseng, and H. P. Chou, “Application of 3D gray mask for the fabrication of curved SU-8 structures,” J. Microsyst. Technol. 11, 365-369 (2005).
[CrossRef]

K. Y. Hung, H. T. Hu, and F. G. Tseng, “Application 3D glycerol-compensated inclined-exposure technology to integrated optical pick-up head,” J. Micromech. Microeng. 14, 975-83 (2004).
[CrossRef]

H. F. Shih, G. D. Lin, C. S. Lu, Y. C. Lee, Y. Chiu, and K. Y. Hung, “Micro objective lens and optical pickup head design for the blue-light small form factor storage system,” in Technical Digest of 6th International Conference on Optics-Photonics Design & Fabrication (Optical Society of Japan, 2008), pp. 9-11.

Jiang, K.

C. H. Lee, K. Jiang, and G. J. Davies, “Sidewall roughness characterization and comparison between silicon and SU-8 microcomponents,” Mater. Char. 58, 603-609 (2007).
[CrossRef]

Kang, W. J.

W. J. Kang, E. Rabe, S. Kopetz, and A. Neyer, “Novel exposure methods based on reflection and refraction effects in the field of SU-8 lithography,” J. Micromech. Microeng. 16, 821-831(2006).
[CrossRef]

Kopetz, S.

E. Rabe, S. Kopetz, and A. Neyer, “The generation of mould patterns for multimode optical waveguide components by direct laser writing of SU-8 at 364 nm,” J. Micromech. Microeng. 17, 1664-1670 (2007).
[CrossRef]

W. J. Kang, E. Rabe, S. Kopetz, and A. Neyer, “Novel exposure methods based on reflection and refraction effects in the field of SU-8 lithography,” J. Micromech. Microeng. 16, 821-831(2006).
[CrossRef]

Lee, C. H.

C. H. Lee, K. Jiang, and G. J. Davies, “Sidewall roughness characterization and comparison between silicon and SU-8 microcomponents,” Mater. Char. 58, 603-609 (2007).
[CrossRef]

Lee, Y. C.

H. F. Shih, G. D. Lin, C. S. Lu, Y. C. Lee, Y. Chiu, and K. Y. Hung, “Micro objective lens and optical pickup head design for the blue-light small form factor storage system,” in Technical Digest of 6th International Conference on Optics-Photonics Design & Fabrication (Optical Society of Japan, 2008), pp. 9-11.

Liang, T. H.

K. Y. Hung and T. H. Liang, “Application of inclined-exposure and thick film process for high aspect-ratio micro structures on polymer optic devices,” J. Microsyst. Technol. 14, 1217-1222 (2008).
[CrossRef]

Liao, J. C.

K. Y. Hung and J. C. Liao, “The application of Fresnel equations and anti-reflection technology to improve inclined exposure interface reflection and develop a key component needed for blu-ray dvd--micro-mirrors,” J. Micromech. Microeng. 18, 075022 (2008).
[CrossRef]

Lin, G. D.

H. F. Shih, G. D. Lin, C. S. Lu, Y. C. Lee, Y. Chiu, and K. Y. Hung, “Micro objective lens and optical pickup head design for the blue-light small form factor storage system,” in Technical Digest of 6th International Conference on Optics-Photonics Design & Fabrication (Optical Society of Japan, 2008), pp. 9-11.

Lin, W. K.

Y. J. Chuang, F. G. Tseng, J. H. Cheng, and W. K. Lin, “A novel fabrication method of embedded micro-channels by using SU-8 thick-film photoresists,” Sens. Actuators A Phys. 103, 64-69 (2003).
[CrossRef]

Y. J. Chuang, F. G. Tseng, and W. K. Lin “Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination,” J. Microsyst. Technol. 8, 308-313(2002).
[CrossRef]

Lindblom, M.

M. Lindblom, H. M. Hertz, and A. Holmberg, “SU-8 plating mold for high-aspect-ratio nickel zone plates,” J. Microelectron. Eng. 84, 1136-1139 (2007).
[CrossRef]

Lochel, B.

K. D. Vora, B. Lochel, E. C. Harvey, J. P. Hayes, and A. G. Peele, “AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography,” J. Micromech. Microeng. 16, 1975-1983 (2006).
[CrossRef]

Lu, C. S.

H. F. Shih, G. D. Lin, C. S. Lu, Y. C. Lee, Y. Chiu, and K. Y. Hung, “Micro objective lens and optical pickup head design for the blue-light small form factor storage system,” in Technical Digest of 6th International Conference on Optics-Photonics Design & Fabrication (Optical Society of Japan, 2008), pp. 9-11.

Mohr, J.

E. F. Reznikova, J. Mohr, and H. Hein, “Deep photo-lithography characterization of SU-8 resist layers,” J. Microsyst. Technol. 11, 282-291 (2005).
[CrossRef]

Mullins, W. W.

W. W. Mullins, “Flattening of a nearly plane solid surface due to capillarity,” J. Appl. Physi. 30, 77-83 (1959).
[CrossRef]

W. W. Mullins, “Theory of thermal grooving,” J. Appl. Physi. 28, 333-339 (1957).
[CrossRef]

Neyer, A.

E. Rabe, S. Kopetz, and A. Neyer, “The generation of mould patterns for multimode optical waveguide components by direct laser writing of SU-8 at 364 nm,” J. Micromech. Microeng. 17, 1664-1670 (2007).
[CrossRef]

W. J. Kang, E. Rabe, S. Kopetz, and A. Neyer, “Novel exposure methods based on reflection and refraction effects in the field of SU-8 lithography,” J. Micromech. Microeng. 16, 821-831(2006).
[CrossRef]

Park, J. H.

Y. K. Yoon, J. H. Park, and M. G. Allen, “Multidirectional UV lithography for complex 3-D MEMS structures,” J. Microelectromech. Syst. 15, 1121-1130 (2006).
[CrossRef]

Peele, A. G.

K. D. Vora, B. Y. Shew, E. C. Harvey, J. P. Hayes, and A. G. Peele, “Sidewall slopes of SU-8 HARMST using deep x-ray lithography,” J. Micromech. Microeng. 18, 035037 (2008).
[CrossRef]

K. D. Vora, B. Lochel, E. C. Harvey, J. P. Hayes, and A. G. Peele, “AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography,” J. Micromech. Microeng. 16, 1975-1983 (2006).
[CrossRef]

Powell, O.

O. Powell and H. B. Harrison, “Anisotropic etching of {100} and {110} planes in (100) silicon,” J. Micromech. Microeng. 11, 217-220 (2001).
[CrossRef]

Rabe, E.

E. Rabe, S. Kopetz, and A. Neyer, “The generation of mould patterns for multimode optical waveguide components by direct laser writing of SU-8 at 364 nm,” J. Micromech. Microeng. 17, 1664-1670 (2007).
[CrossRef]

W. J. Kang, E. Rabe, S. Kopetz, and A. Neyer, “Novel exposure methods based on reflection and refraction effects in the field of SU-8 lithography,” J. Micromech. Microeng. 16, 821-831(2006).
[CrossRef]

Reznikova, E. F.

E. F. Reznikova, J. Mohr, and H. Hein, “Deep photo-lithography characterization of SU-8 resist layers,” J. Microsyst. Technol. 11, 282-291 (2005).
[CrossRef]

Shew, B. Y.

K. D. Vora, B. Y. Shew, E. C. Harvey, J. P. Hayes, and A. G. Peele, “Sidewall slopes of SU-8 HARMST using deep x-ray lithography,” J. Micromech. Microeng. 18, 035037 (2008).
[CrossRef]

Shih, H. F.

H. F. Shih, G. D. Lin, C. S. Lu, Y. C. Lee, Y. Chiu, and K. Y. Hung, “Micro objective lens and optical pickup head design for the blue-light small form factor storage system,” in Technical Digest of 6th International Conference on Optics-Photonics Design & Fabrication (Optical Society of Japan, 2008), pp. 9-11.

Smy, T.

L. J. Friedrich, S. K. Dew, M. J. Brett, and T. Smy, “A simulation study of copper reflow characteristics in vias,” IEEE Trans. Semicond. Manuf. 12, 353-365 (1999).
[CrossRef]

Strandman, C.

C. Strandman, “Fabrication of 45 mirrors together with well-defined V-grooves using wet anisotropic etching of silicon,” J. Microelectromech. Syst. 4, 213-219 (1995).
[CrossRef]

Tseng, F. G.

K. Y. Hung, F. G. Tseng, and H. P. Chou, “Application of 3D gray mask for the fabrication of curved SU-8 structures,” J. Microsyst. Technol. 11, 365-369 (2005).
[CrossRef]

K. Y. Hung, H. T. Hu, and F. G. Tseng, “Application 3D glycerol-compensated inclined-exposure technology to integrated optical pick-up head,” J. Micromech. Microeng. 14, 975-83 (2004).
[CrossRef]

Y. J. Chuang, F. G. Tseng, J. H. Cheng, and W. K. Lin, “A novel fabrication method of embedded micro-channels by using SU-8 thick-film photoresists,” Sens. Actuators A Phys. 103, 64-69 (2003).
[CrossRef]

Y. J. Chuang, F. G. Tseng, and W. K. Lin “Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination,” J. Microsyst. Technol. 8, 308-313(2002).
[CrossRef]

Vora, K. D.

K. D. Vora, B. Y. Shew, E. C. Harvey, J. P. Hayes, and A. G. Peele, “Sidewall slopes of SU-8 HARMST using deep x-ray lithography,” J. Micromech. Microeng. 18, 035037 (2008).
[CrossRef]

K. D. Vora, B. Lochel, E. C. Harvey, J. P. Hayes, and A. G. Peele, “AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography,” J. Micromech. Microeng. 16, 1975-1983 (2006).
[CrossRef]

Wang, W. J.

R. Yang and W. J. Wang, “A numerical and experimental study on gap compensation and wavelength selection in UV-lithography of ultra-high aspect ratio SU-8 microstructures,” Sens. Actuators B Chem. 110, 279-288 (2005).
[CrossRef]

Yang, R.

R. Yang and W. J. Wang, “A numerical and experimental study on gap compensation and wavelength selection in UV-lithography of ultra-high aspect ratio SU-8 microstructures,” Sens. Actuators B Chem. 110, 279-288 (2005).
[CrossRef]

Yoon, Y. K.

Y. K. Yoon, J. H. Park, and M. G. Allen, “Multidirectional UV lithography for complex 3-D MEMS structures,” J. Microelectromech. Syst. 15, 1121-1130 (2006).
[CrossRef]

IEEE Trans. Semicond. Manuf.

L. J. Friedrich, S. K. Dew, M. J. Brett, and T. Smy, “A simulation study of copper reflow characteristics in vias,” IEEE Trans. Semicond. Manuf. 12, 353-365 (1999).
[CrossRef]

J. Appl. Physi.

W. W. Mullins, “Theory of thermal grooving,” J. Appl. Physi. 28, 333-339 (1957).
[CrossRef]

W. W. Mullins, “Flattening of a nearly plane solid surface due to capillarity,” J. Appl. Physi. 30, 77-83 (1959).
[CrossRef]

J. Microelectromech. Syst.

Y. K. Yoon, J. H. Park, and M. G. Allen, “Multidirectional UV lithography for complex 3-D MEMS structures,” J. Microelectromech. Syst. 15, 1121-1130 (2006).
[CrossRef]

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Partially based on the following paper presented at μTAS 2009 Conference: K. Y. Hung, et al., “Application of the surface free energy minimization principle to improve sidewall indentation of polymer inclined mirrors,” The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences (μTAS 2009), Jeju Island, Korea, 1-5 November, 2009.

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Figures (9)

Fig. 1
Fig. 1

(a) Schematic of the light under inclined exposure due to diffraction and interface reflection. In the figure, the light is incident on the surface at θ i . Light will pass through the glycerol ( n gly ), mask ( n m ), gap (filled with glycerol), thickness D of SU-8 ( n s u 8 ), and glass substrate ( n gla ). The incident angle of the light between the SU-8 and the gap is θ e ; the refractive angle is ϑ refr . The angle of the light reflected between the SU-8 and the glass substrate is ϑ refl . The solid line shows the path of the light, including the reflection from the SU-8/glass substrate interface. The dotted line shows the indentation exposure structure resulting from the reflection and diffraction (because of its symmetry, only the left half of the exposed area is shown). (b) Schematic of the light under inclined exposure after improving the interface reflection and gap compensation and using the reflow process.

Fig. 2
Fig. 2

(a) Reflow toward the minimum surface energy and direction of molecular movement. (b) Diagram of the reflow mechanism: 1, surface diffusion; 2, molecular volume diffusion; and 3, viscosity flow.

Fig. 3
Fig. 3

(a) Spectrum distribution of the mercury vapor lamp. (b) Spectrum distribution of the OMEGA PL-360LP filter (OMEGA Inc.). (c) Concept of long-wavelength light penetrating effectively into UV stabilized or pigmented films.

Fig. 4
Fig. 4

Fabrication process for the micromirror. (a) Spin coating of an antireflection layer on the glass substrate. (b) Spin coating of the SU-8 thick-film photoresist. (c) Soft bake. (d) Inclined exposure. (e) Post-exposure baking. (f) Developing process. (g) Reflow.

Fig. 5
Fig. 5

SEM images of the fabricated mirrors when the aligner was used with a filter and high-resolution e-beam mask. Because the mirror device is small, clamps often create abrasions or damage due to falls. Therefore, there are flaws in the SEM or WYKO pictures.

Fig. 6
Fig. 6

WYKO measurement of the 3D roughness when the aligner was used with a filter and a high-resolution e-beam mask. Note the very large indentation on the inclined sidewall. The maximum height of the profile R t is about 13.84 μm (measure length: 1.3 mm ). Therefore, the poor roughness obtained from the 2D measured profile was mainly due to the oversized indentation. Variables are as defined in Table 1. To compare the quality of the manufactured device with those in the related literature, the measurements of area and roughness were prior to those determined using previously published methods [8, 9, 10, 11, 12, 13, 14, 15].

Fig. 7
Fig. 7

(a) WYKO interferometry measurements of the surface roughness of the inclined surface of a micromirror before the reflow (2D). (b) WYKO interferometry measurements of the surface roughness of the inclined surface of a micromirror after the reflow (2D) ( R a = 19.01 nm ). The reflow used in this paper was done at 200 ° C for 80 min.

Fig. 8
Fig. 8

Two-point WYKO interferometry measurements (x direction) of the indentation surface of the mirror (a) before the reflow (measure length: 270 μm ( 0 270 μm ) , R t = 0.81 μm , R p = 0.55 μm , and R v = 1.35 μm ) and (b) after the reflow (measure length: 270 μm ( 10 280 μm ) , R t = 0.08 μm , R p = 0.04 μm , and R v = 0.04 μm ).

Fig. 9
Fig. 9

(a) Fabricated pairs of polymer micromirror surfaces. (b) Relationship between the micromirrors and micro pickup head.

Tables (2)

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Table 1 Comparisons of the Roughness (1D and 2D Measures) of Micromirrors Fabricated by Different Process Technologies (as Measured by WYKO) a

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Table 2 Comparison of the Roughness of Micromirrors Fabricated in Different Studies

Equations (2)

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J s = D s · V · ν k T ( thermal _ energy ) ( chemical _ potential = 2 · V · free _ energy · κ s ) ,
R a = 1 L 0 L f ( x ) = y 1 + y 2 + + y L L ,

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