Abstract

The fabrication of refractive microlens arrays by the technique of excimer laser ablation of doped amorphous Teflon combined with the subsequent annealing and melting of the produced polymer islands is described. The microlenses obtained are optically clear from the far UV (190 m) to the near IR (2000 nm) and are of good optical quality. They vary in size from 50 to 385 μm in diameter with numerical apertures between 0.2 and 0.3. Utilization of these microlenses for material processing by excimer lasers at 193 nm is demonstrated, and possible applications are discussed.

© 1993 Optical Society of America

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References

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  1. J. S. Leggatt, M. C. Hutley, “Microlens arrays for interconnection of single-mode fiber arrays,” Electron. Lett. 27, 238–240 (1991).
    [CrossRef]
  2. D. R. Wisley, “32 Channel WDM multiplexer with 1 nm channel spacing and 0.7 nm bandwidth,” Electron. Lett. 27, 520–521 (1991).
    [CrossRef]
  3. T. Shino, K. Setsune, O. Yamazaki, K. Wasa, “Rectangular-apertured micro-Fresnel lens arrays fabricated by electron-beam lithography,” Appl. Opt. 26, 587–591 (1987).
    [CrossRef]
  4. J. Jahns, S. J. Walker, “Two-dimensional array of diffractive microlenses fabricated by thin film deposition,” Appl. Opt. 29, 931–936 (1990).
    [CrossRef] [PubMed]
  5. M. B. Stern, M. Holz, S. S. Medeiros, R. E. Knowlden, “Fabrication of binary optics: process variables critical to optical efficiency,” J. Vac. Sci. Technol. B 9, 3117–3121 (1991).
    [CrossRef]
  6. Z. D. Popovic, R. A. Sprague, G. A. Neville Connell, “Technique for monolithic fabrication of microlens arrays,” Appl. Opt. 27, 1281–1284 (1988).
    [CrossRef] [PubMed]
  7. D. Daly, R. F. Stevens, M. C. Hutley, N. Davies, “The manufacture of microlenses by melting photoresist,” J. Phys. E. 1, 759–766 (1990).
  8. S. Lazare, V. Granier, “UV laser photoablation of polymers: a review and recent results,” Laser Chem. 10, 25–41 (1989).
    [CrossRef]
  9. P. R. Resnick, “The preparation and properties of anew family of amorphous fluoropolymers: Teflon AF,” Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 31, 312–313 (1990).
  10. “Teflon AF amorphous fluoropolymers,” Du Pont Bull. H-16577 (Du Pont de Nemours and Company, Wilmington, Del., 1990).
  11. J. E. Andrew, P. E. Dyer, D. Forster, P. H. Key, “Direct photoetching of polymeric materials using a XeCl laser,” Appl. Phys. Lett. 43 (8), 717–719 (1983).
    [CrossRef]
  12. J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
    [CrossRef]
  13. J. H. Brannon, J. R. Lankard, “Pulsed CO2 laser etching of polyimide,” Appl. Phys. Lett. 48 (18), 1226–1228 (1986).
    [CrossRef]
  14. P. E. Dyer, G. A. Odlershaw, J. Sidhu, “CO2 laser ablative etching of PET,” Appl. Phys. B 48, 489–493 (1989).
    [CrossRef]
  15. R. Srinivasan, B. Braren, “UV laser ablation and etching of PMMA sensitized with an organic dopant,” Appl. Phys. A 45, 289–292 (1988).
    [CrossRef]
  16. T. J. Chuang, H. Hiraoka, A. Modi, “Laser photoetching characteristics of polymers with dopants,” Appl. Phys. A 45, 277–288 (1988).
    [CrossRef]
  17. H. Hiraoka, S. Lazare, “Applications of doping and dedoping of Teflon AF films in microfabrication using KrF and ArF excimer lasers,” Appl. Surf. Sci. 46, 342–347 (1990).
    [CrossRef]
  18. M. Born, E. Wolf, Principles of Optics (Pergamon, London, 1984), Chap. 13.
  19. P. T. Rumsby, M. C. Gower, “Excimer laser projector for microelectronics applications,” Lasers in Manufacturing, B. Braren, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1598, 36–45 (1991).

1991 (3)

J. S. Leggatt, M. C. Hutley, “Microlens arrays for interconnection of single-mode fiber arrays,” Electron. Lett. 27, 238–240 (1991).
[CrossRef]

D. R. Wisley, “32 Channel WDM multiplexer with 1 nm channel spacing and 0.7 nm bandwidth,” Electron. Lett. 27, 520–521 (1991).
[CrossRef]

M. B. Stern, M. Holz, S. S. Medeiros, R. E. Knowlden, “Fabrication of binary optics: process variables critical to optical efficiency,” J. Vac. Sci. Technol. B 9, 3117–3121 (1991).
[CrossRef]

1990 (4)

D. Daly, R. F. Stevens, M. C. Hutley, N. Davies, “The manufacture of microlenses by melting photoresist,” J. Phys. E. 1, 759–766 (1990).

P. R. Resnick, “The preparation and properties of anew family of amorphous fluoropolymers: Teflon AF,” Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 31, 312–313 (1990).

J. Jahns, S. J. Walker, “Two-dimensional array of diffractive microlenses fabricated by thin film deposition,” Appl. Opt. 29, 931–936 (1990).
[CrossRef] [PubMed]

H. Hiraoka, S. Lazare, “Applications of doping and dedoping of Teflon AF films in microfabrication using KrF and ArF excimer lasers,” Appl. Surf. Sci. 46, 342–347 (1990).
[CrossRef]

1989 (2)

P. E. Dyer, G. A. Odlershaw, J. Sidhu, “CO2 laser ablative etching of PET,” Appl. Phys. B 48, 489–493 (1989).
[CrossRef]

S. Lazare, V. Granier, “UV laser photoablation of polymers: a review and recent results,” Laser Chem. 10, 25–41 (1989).
[CrossRef]

1988 (3)

Z. D. Popovic, R. A. Sprague, G. A. Neville Connell, “Technique for monolithic fabrication of microlens arrays,” Appl. Opt. 27, 1281–1284 (1988).
[CrossRef] [PubMed]

R. Srinivasan, B. Braren, “UV laser ablation and etching of PMMA sensitized with an organic dopant,” Appl. Phys. A 45, 289–292 (1988).
[CrossRef]

T. J. Chuang, H. Hiraoka, A. Modi, “Laser photoetching characteristics of polymers with dopants,” Appl. Phys. A 45, 277–288 (1988).
[CrossRef]

1987 (1)

1986 (1)

J. H. Brannon, J. R. Lankard, “Pulsed CO2 laser etching of polyimide,” Appl. Phys. Lett. 48 (18), 1226–1228 (1986).
[CrossRef]

1985 (1)

J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
[CrossRef]

1983 (1)

J. E. Andrew, P. E. Dyer, D. Forster, P. H. Key, “Direct photoetching of polymeric materials using a XeCl laser,” Appl. Phys. Lett. 43 (8), 717–719 (1983).
[CrossRef]

Andrew, J. E.

J. E. Andrew, P. E. Dyer, D. Forster, P. H. Key, “Direct photoetching of polymeric materials using a XeCl laser,” Appl. Phys. Lett. 43 (8), 717–719 (1983).
[CrossRef]

Baise, A. I.

J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
[CrossRef]

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, London, 1984), Chap. 13.

Brannon, J. H.

J. H. Brannon, J. R. Lankard, “Pulsed CO2 laser etching of polyimide,” Appl. Phys. Lett. 48 (18), 1226–1228 (1986).
[CrossRef]

J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
[CrossRef]

Braren, B.

R. Srinivasan, B. Braren, “UV laser ablation and etching of PMMA sensitized with an organic dopant,” Appl. Phys. A 45, 289–292 (1988).
[CrossRef]

Burns, F.

J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
[CrossRef]

Chuang, T. J.

T. J. Chuang, H. Hiraoka, A. Modi, “Laser photoetching characteristics of polymers with dopants,” Appl. Phys. A 45, 277–288 (1988).
[CrossRef]

Daly, D.

D. Daly, R. F. Stevens, M. C. Hutley, N. Davies, “The manufacture of microlenses by melting photoresist,” J. Phys. E. 1, 759–766 (1990).

Davies, N.

D. Daly, R. F. Stevens, M. C. Hutley, N. Davies, “The manufacture of microlenses by melting photoresist,” J. Phys. E. 1, 759–766 (1990).

Dyer, P. E.

P. E. Dyer, G. A. Odlershaw, J. Sidhu, “CO2 laser ablative etching of PET,” Appl. Phys. B 48, 489–493 (1989).
[CrossRef]

J. E. Andrew, P. E. Dyer, D. Forster, P. H. Key, “Direct photoetching of polymeric materials using a XeCl laser,” Appl. Phys. Lett. 43 (8), 717–719 (1983).
[CrossRef]

Forster, D.

J. E. Andrew, P. E. Dyer, D. Forster, P. H. Key, “Direct photoetching of polymeric materials using a XeCl laser,” Appl. Phys. Lett. 43 (8), 717–719 (1983).
[CrossRef]

Gower, M. C.

P. T. Rumsby, M. C. Gower, “Excimer laser projector for microelectronics applications,” Lasers in Manufacturing, B. Braren, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1598, 36–45 (1991).

Granier, V.

S. Lazare, V. Granier, “UV laser photoablation of polymers: a review and recent results,” Laser Chem. 10, 25–41 (1989).
[CrossRef]

Hiraoka, H.

H. Hiraoka, S. Lazare, “Applications of doping and dedoping of Teflon AF films in microfabrication using KrF and ArF excimer lasers,” Appl. Surf. Sci. 46, 342–347 (1990).
[CrossRef]

T. J. Chuang, H. Hiraoka, A. Modi, “Laser photoetching characteristics of polymers with dopants,” Appl. Phys. A 45, 277–288 (1988).
[CrossRef]

Holz, M.

M. B. Stern, M. Holz, S. S. Medeiros, R. E. Knowlden, “Fabrication of binary optics: process variables critical to optical efficiency,” J. Vac. Sci. Technol. B 9, 3117–3121 (1991).
[CrossRef]

Hutley, M. C.

J. S. Leggatt, M. C. Hutley, “Microlens arrays for interconnection of single-mode fiber arrays,” Electron. Lett. 27, 238–240 (1991).
[CrossRef]

D. Daly, R. F. Stevens, M. C. Hutley, N. Davies, “The manufacture of microlenses by melting photoresist,” J. Phys. E. 1, 759–766 (1990).

Jahns, J.

Kaufman, J.

J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
[CrossRef]

Key, P. H.

J. E. Andrew, P. E. Dyer, D. Forster, P. H. Key, “Direct photoetching of polymeric materials using a XeCl laser,” Appl. Phys. Lett. 43 (8), 717–719 (1983).
[CrossRef]

Knowlden, R. E.

M. B. Stern, M. Holz, S. S. Medeiros, R. E. Knowlden, “Fabrication of binary optics: process variables critical to optical efficiency,” J. Vac. Sci. Technol. B 9, 3117–3121 (1991).
[CrossRef]

Lankard, J. R.

J. H. Brannon, J. R. Lankard, “Pulsed CO2 laser etching of polyimide,” Appl. Phys. Lett. 48 (18), 1226–1228 (1986).
[CrossRef]

J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
[CrossRef]

Lazare, S.

H. Hiraoka, S. Lazare, “Applications of doping and dedoping of Teflon AF films in microfabrication using KrF and ArF excimer lasers,” Appl. Surf. Sci. 46, 342–347 (1990).
[CrossRef]

S. Lazare, V. Granier, “UV laser photoablation of polymers: a review and recent results,” Laser Chem. 10, 25–41 (1989).
[CrossRef]

Leggatt, J. S.

J. S. Leggatt, M. C. Hutley, “Microlens arrays for interconnection of single-mode fiber arrays,” Electron. Lett. 27, 238–240 (1991).
[CrossRef]

Medeiros, S. S.

M. B. Stern, M. Holz, S. S. Medeiros, R. E. Knowlden, “Fabrication of binary optics: process variables critical to optical efficiency,” J. Vac. Sci. Technol. B 9, 3117–3121 (1991).
[CrossRef]

Modi, A.

T. J. Chuang, H. Hiraoka, A. Modi, “Laser photoetching characteristics of polymers with dopants,” Appl. Phys. A 45, 277–288 (1988).
[CrossRef]

Neville Connell, G. A.

Odlershaw, G. A.

P. E. Dyer, G. A. Odlershaw, J. Sidhu, “CO2 laser ablative etching of PET,” Appl. Phys. B 48, 489–493 (1989).
[CrossRef]

Popovic, Z. D.

Resnick, P. R.

P. R. Resnick, “The preparation and properties of anew family of amorphous fluoropolymers: Teflon AF,” Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 31, 312–313 (1990).

Rumsby, P. T.

P. T. Rumsby, M. C. Gower, “Excimer laser projector for microelectronics applications,” Lasers in Manufacturing, B. Braren, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1598, 36–45 (1991).

Setsune, K.

Shino, T.

Sidhu, J.

P. E. Dyer, G. A. Odlershaw, J. Sidhu, “CO2 laser ablative etching of PET,” Appl. Phys. B 48, 489–493 (1989).
[CrossRef]

Sprague, R. A.

Srinivasan, R.

R. Srinivasan, B. Braren, “UV laser ablation and etching of PMMA sensitized with an organic dopant,” Appl. Phys. A 45, 289–292 (1988).
[CrossRef]

Stern, M. B.

M. B. Stern, M. Holz, S. S. Medeiros, R. E. Knowlden, “Fabrication of binary optics: process variables critical to optical efficiency,” J. Vac. Sci. Technol. B 9, 3117–3121 (1991).
[CrossRef]

Stevens, R. F.

D. Daly, R. F. Stevens, M. C. Hutley, N. Davies, “The manufacture of microlenses by melting photoresist,” J. Phys. E. 1, 759–766 (1990).

Walker, S. J.

Wasa, K.

Wisley, D. R.

D. R. Wisley, “32 Channel WDM multiplexer with 1 nm channel spacing and 0.7 nm bandwidth,” Electron. Lett. 27, 520–521 (1991).
[CrossRef]

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, London, 1984), Chap. 13.

Yamazaki, O.

Appl. Opt. (3)

Appl. Phys. A (2)

R. Srinivasan, B. Braren, “UV laser ablation and etching of PMMA sensitized with an organic dopant,” Appl. Phys. A 45, 289–292 (1988).
[CrossRef]

T. J. Chuang, H. Hiraoka, A. Modi, “Laser photoetching characteristics of polymers with dopants,” Appl. Phys. A 45, 277–288 (1988).
[CrossRef]

Appl. Phys. B (1)

P. E. Dyer, G. A. Odlershaw, J. Sidhu, “CO2 laser ablative etching of PET,” Appl. Phys. B 48, 489–493 (1989).
[CrossRef]

Appl. Phys. Lett. (2)

J. H. Brannon, J. R. Lankard, “Pulsed CO2 laser etching of polyimide,” Appl. Phys. Lett. 48 (18), 1226–1228 (1986).
[CrossRef]

J. E. Andrew, P. E. Dyer, D. Forster, P. H. Key, “Direct photoetching of polymeric materials using a XeCl laser,” Appl. Phys. Lett. 43 (8), 717–719 (1983).
[CrossRef]

Appl. Surf. Sci. (1)

H. Hiraoka, S. Lazare, “Applications of doping and dedoping of Teflon AF films in microfabrication using KrF and ArF excimer lasers,” Appl. Surf. Sci. 46, 342–347 (1990).
[CrossRef]

Electron. Lett. (2)

J. S. Leggatt, M. C. Hutley, “Microlens arrays for interconnection of single-mode fiber arrays,” Electron. Lett. 27, 238–240 (1991).
[CrossRef]

D. R. Wisley, “32 Channel WDM multiplexer with 1 nm channel spacing and 0.7 nm bandwidth,” Electron. Lett. 27, 520–521 (1991).
[CrossRef]

J. Appl. Phys. (1)

J. H. Brannon, J. R. Lankard, A. I. Baise, F. Burns, J. Kaufman, “Excimer laser etching of polyimide,” J. Appl. Phys. 58 (5), 2036–2043 (1985).
[CrossRef]

J. Phys. E. (1)

D. Daly, R. F. Stevens, M. C. Hutley, N. Davies, “The manufacture of microlenses by melting photoresist,” J. Phys. E. 1, 759–766 (1990).

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

M. B. Stern, M. Holz, S. S. Medeiros, R. E. Knowlden, “Fabrication of binary optics: process variables critical to optical efficiency,” J. Vac. Sci. Technol. B 9, 3117–3121 (1991).
[CrossRef]

Laser Chem. (1)

S. Lazare, V. Granier, “UV laser photoablation of polymers: a review and recent results,” Laser Chem. 10, 25–41 (1989).
[CrossRef]

Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. (1)

P. R. Resnick, “The preparation and properties of anew family of amorphous fluoropolymers: Teflon AF,” Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 31, 312–313 (1990).

Other (3)

“Teflon AF amorphous fluoropolymers,” Du Pont Bull. H-16577 (Du Pont de Nemours and Company, Wilmington, Del., 1990).

M. Born, E. Wolf, Principles of Optics (Pergamon, London, 1984), Chap. 13.

P. T. Rumsby, M. C. Gower, “Excimer laser projector for microelectronics applications,” Lasers in Manufacturing, B. Braren, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1598, 36–45 (1991).

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Figures (9)

Fig. 1
Fig. 1

Schematic diagram of the experimental system used for patterning doped amorphous Teflon with ArF excimer laser radiation and fused silica projection optics: LA, Lambda Physik EMG200 excimer laser operating with an ArF gas mixture at 193 nm; L­1 prefocus lens (focal length f1 = 10 cm), M, object mask; I, iris; L2, L3, imaging lenses (f2 = f3 = 25 cm); FP, polymer film plane.

Fig. 2
Fig. 2

SEM photomicrographs of the various stages of the microlens-formation process: (a) The initial ablation pattern of octagonal polymer islands etched in Teflon AT with 50% dopant by mass, (b) Polymer islands after dedoping is performed at 160 °C for 20 min. (c) The final lenses after being at a melt temperature of 300 °C for 20 min. In (a)–(c) the samples are tilted 60° with respect to the normal and scaling is 100 μm full scale.

Fig. 3
Fig. 3

Changes in the contact angle of doped Teflon with a silicon substrate as a function of time and temperature. We performed these measurements optically by viewing cross-sectional cuts made in the doped polymer film. There is a ± 4° error in each data point. The curve is drawn solely to guide the eye.

Fig. 4
Fig. 4

Percentage change in mass and thickness of doped Teflon as a function of time and temperature. Thickness changes were measured in the optical fashion as in Fig. 3 and are denoted by filled circles. There is a ±7% error in each data point. The curve is a nonlinear regression calculation fitted to the expression % thickness = A exp(−Bt) + C, where A = 37.2 μm, B = 0.0304 min−1, C = 54.8 μm, and t is the time in minutes. The points denoted by open squares are the changes in mass as measured with a microbalance. The connecting curve is drawn to guide the eye.

Fig. 5
Fig. 5

Magnified SEM photomicrograph of a single microlens as seen in Fig. 2(c). The sample is perpendicular with respect to the normal, and the scaling is 100 μm full scale.

Fig. 6
Fig. 6

Cross-sectional profile of a typical microlens as measured with the stylus profilometer. The solid curve denotes the actual data, while the dotted curve is the theoretical spherical curve for a lens with the same base diameter d and height h. The scales are in units of micrometer.

Fig. 7
Fig. 7

Absorption spectra (absorbance versus wavelength) of doped Teflon in the UV–visible region. The solid curve in (a) represents the absorption of an amorphous Teflon film with 50% dopant by mass and a thickness of 35 μm, while the dotted curve is a dedoped and melted film with a thickness of 65 μm. In (b) the solid curve represents the absorption of a pure amorphous Teflon film (60-μm thickness) compared with the same dedoped and melted film absorption as seen in (a).

Fig. 8
Fig. 8

Images of the logo of the Centre National de la Recerche Scientifique viewed through an optical microscope, showing the imaging capability of the microlens array.

Fig. 9
Fig. 9

SEM photomicrographs of the etch patterns generated in Mylar D films by focusing ArF excimer-laser radiation through the microlens array: (a) The ablative surface modification of near-fluence threshold radiation surrounding the shadows generated by each lens on the surface. The scaling is 100 μm full scale, and the viewing angle is at 45° to the normal, (b) Magnified image of the ablation pattern generated within the lens-shadow region. The scaling is 10 μm full scale, and the viewing angle is at 45° to the normal.

Tables (1)

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Table 1 Surface Reflectivity ℜ and Transmission T of ArF Exclmer-Laser Radiation off of Several Samples of Thickness t in Micrometersa

Equations (5)

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= | n ˆ 2 n ˆ 1 n ˆ 2 + n ˆ 1 | 2 = ( n 2 n 1 ) 2 + ( k 2 k 1 ) 2 ( n 2 n 1 ) 2 + ( k 2 k 1 ) 2 ,
f = R n ˆ 1 ,
R = d 2 + 4 h 2 8 h .
T = exp ( α t ) .
NA = n 0 sin θ max = d ( d 2 + 4 f 2 ) 1 / 2 ,

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