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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 12 — Jun. 6, 2011
  • pp: 11897–11905
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Spherical silicon micromirrors bent by anodic bonding

Tong Wu, Takahiro Yamasaki, Ryohei Hokari, and Kazuhiro Hane  »View Author Affiliations


Optics Express, Vol. 19, Issue 12, pp. 11897-11905 (2011)
http://dx.doi.org/10.1364/OE.19.011897


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Abstract

We propose here a novel and stable method for fabricating spherical micromirror by bonding a flat freestanding single-crystal-silicon (SCS) membrane with a fulcrum on a glass substrate. Smooth convex spherical surface is achieved inside the fulcrum by the bending moment generated in the circumference of the SCS membrane. The surface profiles fit well with parabolic curves within 36nm RMS error indicating a good optical performance. By modifying the diameter of the fulcrum, we also demonstrate that it is possible to fabricate micromirrors with a wide range of focal length (0.4mm-1.6mm). The fabricated micromirrors are also used as the mold for replication of micro polymeric lenses. The surface profiles of the micromirrors are transferred to the polymeric replica with a high accuracy.

© 2011 OSA

1. Introduction

Spherical micromirror and microlens have been key components for micro-optics and optical microelectromechanical systems (MEMS). Several fabrication techniques of spherical micromirror and microlens have been developed. The most common method was re-flowing resist polymer and subsequently transferring the polymer shape to substrate by plasma etching [1

1. H. P. Herzig, Micro-optics (Taylor&Francis, 1997).

,2

2. S. Audran, B. Faure, B. Mortini, J. Regolini, G. Schlatter, and G. Hadziioannou, “Study of mechanisms involved in photoresist microlens formation,” Microelectron. Eng. 83(4-9), 1087–1090 (2006). [CrossRef]

]. Gray scale mask was also used to generate a lens-shaped resist polymer [3

3. G. Wang, S. Wang, and C.-H. Chin, “Fabrication and molding of gray-scale mask based aspheric refraction micro-lens array,” JSME Int. J., Ser. C 46(4), 1598–1603 (2003). [CrossRef]

5

5. T.-W. Lin, C.-F. Chen, J.-J. Yang, and Y.-S. Liao, “A dual-directional light-control film with a high-sag and high-asymmetrical-shape microlens array fabricated by a UV imprinting process,” J. Micromech. Microeng. 18(9), 095029 (2008). [CrossRef]

]. However, in case for fabricating mirror and lens with a high aspect ratio, the surface quality needed for specular reflection and refraction are often degraded by the etching since the deep etching enlarges the initial small roughness [6

6. Y. Kanamori, J. Sato, T. Shimano, S. Nakamura, and K. Hane, “Polymer microstructure generated by laser stereo-lithography and its transfer to silicon substrate using reactive ion etching,” Microsyst. Technol. 13(8-10), 1411–1416 (2007). [CrossRef]

]. Moreover, the deep-etched shape often deviated from spherical surface. Another self-shaping method known as inkjet process was demonstrated as an effective method without the subsequent transferring process [7

7. S. Biehl, R. Danzebrink, P. Oliveira, and M. A. Aegerter, “Refractive Microlens Fabrication by Ink-Jet Process,” J. Sol-Gel Sci. Technol. 13(1/3), 177–182 (1998). [CrossRef]

,8

8. C.-T. Chen, Z.-F. Tseng, C.-L. Chiu, C.-Y. Hsu, and C.-T. Chuang, “Self-aligned hemispherical formation of microlenses from colloidal droplets on heterogeneous surfaces,” J. Micromech. Microeng. 19(2), 025002 (2009). [CrossRef]

]. This process needs an accurate control of the rheological properties (viscosity, surface tension) and the volume of the dispensing material, making the fabrication of a high-precision spherical surface a challenging task. Molding or embossing materials was presented as another approach for fabricating microlens which ganrantees a better surface roughness than that of plasma etching [9

9. S. Lee, Y.-C. Jeong, and J.-K. Park, “Facile fabrication of close-packed microlens arrays using photoinduced surface relief structures as templates,” Opt. Express 15(22), 14550–14559 (2007). [CrossRef] [PubMed]

13

13. J.-T. Wu, W.-Y. Chang, and S.-Y. Yang, “Fabrication of a nano/micro hybrid lens using gas-assisted hot embossing with an anodic aluminum oxide (AAO) template,” J. Micromech. Microeng. 20(7), 075023 (2010). [CrossRef]

]. P. Merz et al demonstrated reflowing glass into silicon mold as an effective approach for generating a high aspect ratio spherical lens [12

12. P. Merz, H. J. Quenzer, H. Bernt, B. Wagner, and M. Zoberbier, “A novel micromachining technology for structuring borosilicate glass substrates,” in Proceedings of IEEE Conference on Solid State Sensors, Actuators and Microsystems (IEEE, 2003), pp.258–261.

]. J.-T. Wu et al reported a polymeric lens with sub-wavelength structures (SWSs) on the surface using hot embossing method [13

13. J.-T. Wu, W.-Y. Chang, and S.-Y. Yang, “Fabrication of a nano/micro hybrid lens using gas-assisted hot embossing with an anodic aluminum oxide (AAO) template,” J. Micromech. Microeng. 20(7), 075023 (2010). [CrossRef]

].

SOI(silicon on insulator) technology have boosted the development of MEMS micromirror and deformable mirror as it allows a simple process for fabricating freestanding structure and provides a flat stressless single-crystal-silicon (SCS) device layer with good optical quality and mechanical property. L. Wu et al demonstrated an electrothermally actuated tip-tilt-piston micromirror array based on SOI technology [14

14. L. Wu, S. Dooley, E. A. Watson, P. F. McManamon, and H. Xie, “A Tip-Tilt-Piston Micromirror Array for Optical Phased Array Applications,” J. Microelectromech. Syst. 19(6), 1450–1461 (2010). [CrossRef]

]. H.M. Chu et al presented a SOI-based micromirror for laser display application [15

15. H. M. Chu, T. Tokuda, M. Kimata, and K. Hane, “Compact Low-Voltage Operation Micromirror Based on High-Vacuum Seal Technology Using Metal Can,” J. Microelectromech. Syst. 19(4), 927–935 (2010). [CrossRef]

]. Furthermore, bending of SCS membrane can generate a smoothly curved surface due to its inherent large elasticity, which was commonly used for the deformable mirror and varifocal mirror [16

16. Y. Hishinuma and E.-H. Yang, “Piezoelectric unimorph microactuator arrays for single-crystal silicon continuous-membrane deformable mirror,” J. Microelectromech. Syst. 15(2), 370–379 (2006). [CrossRef]

,17

17. I. W. Jung, Y.-A. Peter, E. Carr, J.-S. Wang, and O. Solgaard, “Single-Crystal-Silicon Continuous Membrane Deformable Mirror Array for Adaptive Optics in Space-Based Telescopes,” IEEE J. Sel. Top. Quantum Electron. 13(2), 162–167 (2007). [CrossRef]

]. An accurately spherical varifocal mirror was recently reported using the bend of SCS membrane with fulcrum [18

18. R. Hokari and K. Hane, “A varifocal convex micromirror driven by a bending moment,” IEEE J. Sel. Top. Quantum Electron. 15(5), 1310–1316 (2009). [CrossRef]

]. Due to the shape generated by the bending moment, the mirror is uniformly spherical inside the fulcrum. Another approach for generating smooth mirror surface by bending thin SCS membrane using metal pad was also experimentally demonstrated in our recent work [19

19. T.Wu, K.Hane, “High-precise spherical micromirror by bending silicon plate with metal pad,” (to be published).

]. However, the focal length was large (>5mm) due to the thin metal pad.

In this study, we propose a fabrication technique for spherical convex micromirror with a small focal length (~0.4mm) combining anodic bonding process and SOI technology. SCS membrane of a SOI wafer is curved into a spherical shape by bonding it on a glass substrate with a circular fulcrum. Theoretical model is constructed for analyze the surface, which is demonstrated to be an approximate spherical surface theoretically. Due to the large yielding stress of SCS, the micromirrors with a high aspect ratio are generated, as well as a smooth and low-roughness surface. Furthermore, the fabricated micromirror is used as a mold for the replication of polymeric lens. The profiles of the fabricated micromirror and polymeric lens are measured by an interferometer and evaluated by fitting them with parabolic curves.

2. Principle and design

Figure 1
Fig. 1 Fabrication method of convex micromirror, (a)before bonding; (b) after bonding.
shows the fabrication method for the proposed spherical micromirror. A glass substrate is etched to form a circular fulcrum with a radius of a and a circular SCS membrane with a radius of b is placed on the fulcrum with a height of has shown in Fig. 1 (a). A dc voltage is applied between the SCS membrane and the glass substrate to bond the circumference of the circular membrane as shown in Fig. 1 (b). Due to the bending with a rotation-free fulcrum, the SCS membrane is deflected like a convex mirror by the bending moment inside the fulcrum.

This situation can be simply considered as a statically indeterminate beam problem as illustrated in Fig. 2
Fig. 2 Theoretical calculation model.
. The beam is fixed at both end and two concentrated forces W are applied on it at the points corresponding to the position of the fulcrum. Simultaneously, there ought to be forces W' and bending moments Mcacting on both of the fixed ends to keep the balance of the beam as shown in Fig. 2. Considering the symmetrical characteristic of this problem, we can get W'=W using the balance of force. Based on the strength of materials, the moment Mc can be solved as
Mc=d(2a+d)2(a+d)W,
(1)
where, d illustrates the distance between the contact point and the outside border of the fulcrum as shown in Fig. 1(b). Building an orthogonal coordinate system as shown in Fig. 1 (b), the bending moment Mcan be calculated as

M={W[|x|2a2+2ad+d22(a+d)]   ,(a |x|a+d)Wd22(a+d)                    ,(|x|a).
(2)

By solving the equation
d2ydx2=MEI,
(3)
whereE and Irepresent the Young’s modulus and moment of inertia of the beam, respectively, and utilizing the boundary conditions for the deflection angle θ and the deflection y that,
{θ|x=±(a+d)=0θ|x=0=0
(4)
and
{y|x=±(a+d)=0y|x=±a=h,
(5)
we can get the equation of the deflection y written as a function of a,d and h

y={h4d3(4a+d)[4(a+d)|x|33h(4a2+4ad+d2)|x|2+                    12a2(a+d)|x|2h(a+d)2(2a2add2)],  (a |x|a+d)3h(4a+d)d[x2a213(4a+d)d],                                  (|x|a).
(6)

As expressed by the equation when a |x|a+d, the shape of surface outside the fulcrum is a 3rd-order polynomial surface. The shape of surface inside the fulcrum expressed by the equation when |x|a is demonstrated to be a parabola, the effective focal length fof which can be written as,

f=d3ha+d212h.
(7)

In this equation, because dis determined by the applied voltage in the anodic bonding process, f increases linearly with the increase ofa when a constant voltage is applied. It should be noted that any higher order deflection is not included in the equation when|x|a, which is an approximated equation to the real deflection that is considered to be spherical.

Moreover, we can also get the maximum stress σmax applied on the SCS membrane within the region where |x|a, which is given by
σmax=|M|t/2I=3Ehtd(4a+d),
(8)
where, t stands for the thickness of the SCS membrane.

In designing, the diameters of the SCS membranes are in the range from 449μm to 767μm and the fulcrum diameters are from 50μm to 600μm. The SCS membrane is suspended by narrow suspension beams at its circumference for alignment and bonding.

3. Fabrication procedure

Figure 3(a)
Fig. 3 Fabrication sequence chart for: (a) freestanding SCS membrane, (b) supporting fulcrum, and (c) anodic bonding.
schematically illustrates the fabrication sequence for the freestanding SCS membrane and the glass substrate. To prepare the freestanding SCS membrane, a silicon on insulator (SOI) wafer consisting of 10μm top SCS layer, 2μm buried oxide layer and 200μm silicon handle layer is used. The SCS membranes in diameters from 449μm to 767μm are fabricated by deep reactive ion etching (D-RIE). First, the handle layer is patterned and etched down to the buried oxide to determine the location of the SCS membrane using D-RIE. Subsequently, the top silicon layer is patterned and etched through to define the dimension of the silicon mirror plate. Then, the buried oxide layer is removed to release the SCS membrane by vapor hydrofluoric acid (VHF) etching. The silicon circular plate is suspended to the substrate by narrow suspension beams.

As illustrated in Fig. 3(b), the fabrication process for the glass substrate starts from the sputtering of a ~60nm chrome film on a 100μm thick Pyrex glass. Then the chrome film is patterned and wet etched to form a circular ring to define the supporting fulcrum. As photo resist is often peeled in wet hydrofluoric acid (HF) etching process, the circular chrome ring acts as a hard mask for glass etching. The Pyrex glass is isotropically etched in concentrated hydrofluoric acid and about ~9μm height fulcrum is formed. After removing the chrome mask, a 140nm thick metal film (gold, with ~20μm thick chrome adhesion layer) is deposited and patterned by wet etching which is used as an anti-bonding layer to prevent the SCS membrane from bonding with the fulcrum in the subsequent bonding process. At last, the front surface of the top SCS membrane is bonded to the etched 100μm thick glass substrate by utilizing a typical anodic bonding process [20

20. V. Dragoi, P. Lindner, T. Glinsner, M. Wimplinger, and S. Farrens, “Advanced Anodic Bonding Processes for MEMS Applications,” in Proceedings of Materials Research Society Symposium (Materials Research Society, 2004), 782, pp.A5.80.1–6.

] at the temperature of 400 degree centigrade and the voltage of 890V as illustrated in Fig. 3(c).

4. Results and discussion

Figures 4(a)
Fig. 4 Optical micrographs of the fabricated micromirrors, (a) front side, (b) back side, (c) micromirror array.
and 4(b) show the optical micrographs of the fabricated micromirror taken from the front and back sides, respectively. The diameter of the SCS membrane is 986μm, and the fulcrum is 200μm in diameter and 9μm high. The inner diameter of the bonded area is about 500μm. The gray dots which can be seen in Fig. 4(b) are the particle of graphite sheet used as the cathode in anodic bonding process. The particles can be removed by ultrasonic cleaning.

This fabrication method allows for the fabrication of arrays of micro-lenses. As shown in Fig. 4(c), a micromirror array was actually fabricated in our experiments. Generally, the distance between the circumferences of fulcrum of adjacent mirrors can be set to the minimum length of bonded area verified in our experiment. Let srepresent the distance between the circumferences of the fulcrums. The fill factor α of the mircromirror array with a pitch p=2a+scan be given by

α=πa2(2a+s)2.
(9)

The experiment showed the minimum distance scan be ~150μm to satisfy bonding, and this distance will not change with the change of the diameter of fulcrum. For a 400μm diameter micromirror array, the fill factor can be achieved to be 41.5%.

The shapes of the fabricated micromirrors were measured by using an optical interferometer (Zygo, New View 6000). Figure 5
Fig. 5 Measured surface profiles of the fabricated micromirror, (a) color-coded height distribution; (b) 3D color-coded height profile; (c) profile across the centre of the mirror; (d) profile inside the fulcrum and the fitted parabola.
illustrates the measured results of a 200μm diameter micromirror. Figure 5(a) shows a top view of the height distribution expressed by color-coding. Figure 5(b) shows the 3 Dimensional (3D) height profile of the mirror surface. The missing measurement points which can be seen in Fig. 5(a) and Fig. 5(b) is due to the local high inclination of the surface from where the interferometer cannot receive the reflected light signal. Figure 5(c) is the surface profile across the center of the mirror. The height difference is about 13μm between the center and the edge of the mirror. The surface profile in the region inside the fulcrum is also plotted with a fitted parabola in Fig. 5 (d), which shows that the surface of the mirror is smooth and well approximated by a parabola as expected by Eq. (6). The root mean square (RMS) error deviating from the fitted parabolic curve equals to 36nm. The parabolic fitting has also been implemented for the micromirrors with different diameters from 100μm to 400μm. The RMS deviation from the fitted parabola ranged between 20nm to 40nm randomly with no obvious tendency according to the change of diameter. Furthermore, since the mirror surface is originated from the polished silicon surface and no additional etching is introduced for manufacturing, the surface roughness is thus limited to the polishing error. The surface roughness is obtained from the Zygo data by measuring the arithmetic average roughnessRaof several 100μm length lines across the centre of the mirror. The average value is 2nm.

Micromirrors with different diameters are also fabricated by changing the diameter of the supporting fulcrum. The focal lengths calculated from the measured profiles of the fabricated micromirrors are plotted in solid line as a function of the fulcrum diameter in Fig. 6
Fig. 6 Focal length as a function of fulcrum radius.
. The focal length increases linearly from 0.4mm to 1.6mm with the increase in diameter from 100μm to 400μm. The focal lengths of the fabricated mirrors have not been verified by impinging a light beam. However, we observed a small clear focus light spot when a spherically converging laser beam was impinged on a fabricated mirror. Furthermore, the distancedin Eq. (7) is investigated to be 140μm from the measured profiles. Substituting the value of dand h(9μm) into the Eq. (7), we can derive the theoretical predicting equation of the focal lengthf, which is given by

f=5.19a+181.48 (μm).
(10)

The plot of the theoretically calculatedf is shown in dashed line in Fig. 6, which indicates a slightly larger slope than that of the experimental results. The minimum focal length achieved in our experiment is 400μm. The maximum stress applied on the fabricated mirror plate is also calculated using Eq. (8), which ranges from 740MPa to 230MPa as the corresponding focal length of the mirror ranges from 400μm to 1600μm.

The fundamental limit of this technology comes from the stress limitation of SCS. The maximum stress σmax applied on the SCS membrane should be no larger than the ultimate strength σ0of SCS, that is
σmax=3Ehtd(4a+d)<σ0,
(11)
where, d can be set as d=3/2a according to the average value from our experiments. Therefore, we can obtain the limitation of the radius of fulcrum thata>27 .4μm,and the diameter of the mirror2(a+d)>137.0μm, σ0=7GPa,E=160GPa,h=9μm,and t=10μmare used in this calculation. Moreover, we theoretically calculated the minimum focal length to be ~57μm using the value of ultimate strength of SCS.

Polymeric lens was also fabricated using the fabricated micromirror as a mold by utilizing a micro-replication process. The polymer (OEBE-1000) is filled in the mold after using the exfoliation solution (optool DSX) and rinse (Demnumsolvent, Daikin). One cycle of the replication process cost about 32min including the resin coating time (1min) and the post baking (30min) and peeling (1min) in our experiment. This time can be shortened by using a optimized high volume replication process. Figure 7(a)
Fig. 7 Polymeric replica and the surface profile, (a) optical micrograph of the polymeric microlens; (b) profile across the centre of the microlens; (c) profile inside the fulcrum and the fitted parabola.
shows the optical micrograph of the replica after peeling off, the surface profile of which is plotted in Fig. 7(b). The surface profile inside the fulcrum is plotted in Fig. 6 (c) with a parabola fitted to the measured values, which shows the mold profile is well transferred to the replica with a high accuracy. The root mean square (RMS) error deviating from the fitted parabolic curve equals to 48nm.

5. Conclusion

In summary, a novel approach was theoretically proposed and experimentally demonstrated for fabricating high aspect ratio, precise, spherical micromirror and microlens. Smooth spherical surface was realized by bending SCS membrane. The surface profiles of the fabricated spherical mirrors were well fitted with parabolic curve. The focal lengths range from 0.4mm to 1.6mm with the corresponding diameter ranging from 100μm to 400μm. Moreover, extremely low-roughness (~2nm) mirror surface was guaranteed because no etching process was implemented on it. Polymeric lens was also manufactured using the fabricated mirror as a mold with a high accuracy. The simple bending mechanism for spherical surface generation makes this method a stable and effective approach for the fabrication of micromirror and microlens.

Acknowledgments

The authors thank to Prof. T. Kuriyagawa for the interferometric measurement. The work is supported by JSPS, GCOE and SCFPST.

References and links

1.

H. P. Herzig, Micro-optics (Taylor&Francis, 1997).

2.

S. Audran, B. Faure, B. Mortini, J. Regolini, G. Schlatter, and G. Hadziioannou, “Study of mechanisms involved in photoresist microlens formation,” Microelectron. Eng. 83(4-9), 1087–1090 (2006). [CrossRef]

3.

G. Wang, S. Wang, and C.-H. Chin, “Fabrication and molding of gray-scale mask based aspheric refraction micro-lens array,” JSME Int. J., Ser. C 46(4), 1598–1603 (2003). [CrossRef]

4.

K. Totsu and M. Esashi, “Gray-scale photolithography using maskless exposure system,” J. Vac. Sci. Technol. B 23(4), 1487–1490 (2005). [CrossRef]

5.

T.-W. Lin, C.-F. Chen, J.-J. Yang, and Y.-S. Liao, “A dual-directional light-control film with a high-sag and high-asymmetrical-shape microlens array fabricated by a UV imprinting process,” J. Micromech. Microeng. 18(9), 095029 (2008). [CrossRef]

6.

Y. Kanamori, J. Sato, T. Shimano, S. Nakamura, and K. Hane, “Polymer microstructure generated by laser stereo-lithography and its transfer to silicon substrate using reactive ion etching,” Microsyst. Technol. 13(8-10), 1411–1416 (2007). [CrossRef]

7.

S. Biehl, R. Danzebrink, P. Oliveira, and M. A. Aegerter, “Refractive Microlens Fabrication by Ink-Jet Process,” J. Sol-Gel Sci. Technol. 13(1/3), 177–182 (1998). [CrossRef]

8.

C.-T. Chen, Z.-F. Tseng, C.-L. Chiu, C.-Y. Hsu, and C.-T. Chuang, “Self-aligned hemispherical formation of microlenses from colloidal droplets on heterogeneous surfaces,” J. Micromech. Microeng. 19(2), 025002 (2009). [CrossRef]

9.

S. Lee, Y.-C. Jeong, and J.-K. Park, “Facile fabrication of close-packed microlens arrays using photoinduced surface relief structures as templates,” Opt. Express 15(22), 14550–14559 (2007). [CrossRef] [PubMed]

10.

S.- Moon, N. Lee, and S. Kang, “Fabrication of a microlens array using micro-compression molding with an electroformed mold insert,” J. Micromech. Microeng. 13(1), 98–103 (2003). [CrossRef]

11.

G. C. Firestone and A. Y. Yi, “Precision compression molding of glass microlenses and microlens arrays--an experimental study,” Appl. Opt. 44(29), 6115–6122 (2005). [CrossRef] [PubMed]

12.

P. Merz, H. J. Quenzer, H. Bernt, B. Wagner, and M. Zoberbier, “A novel micromachining technology for structuring borosilicate glass substrates,” in Proceedings of IEEE Conference on Solid State Sensors, Actuators and Microsystems (IEEE, 2003), pp.258–261.

13.

J.-T. Wu, W.-Y. Chang, and S.-Y. Yang, “Fabrication of a nano/micro hybrid lens using gas-assisted hot embossing with an anodic aluminum oxide (AAO) template,” J. Micromech. Microeng. 20(7), 075023 (2010). [CrossRef]

14.

L. Wu, S. Dooley, E. A. Watson, P. F. McManamon, and H. Xie, “A Tip-Tilt-Piston Micromirror Array for Optical Phased Array Applications,” J. Microelectromech. Syst. 19(6), 1450–1461 (2010). [CrossRef]

15.

H. M. Chu, T. Tokuda, M. Kimata, and K. Hane, “Compact Low-Voltage Operation Micromirror Based on High-Vacuum Seal Technology Using Metal Can,” J. Microelectromech. Syst. 19(4), 927–935 (2010). [CrossRef]

16.

Y. Hishinuma and E.-H. Yang, “Piezoelectric unimorph microactuator arrays for single-crystal silicon continuous-membrane deformable mirror,” J. Microelectromech. Syst. 15(2), 370–379 (2006). [CrossRef]

17.

I. W. Jung, Y.-A. Peter, E. Carr, J.-S. Wang, and O. Solgaard, “Single-Crystal-Silicon Continuous Membrane Deformable Mirror Array for Adaptive Optics in Space-Based Telescopes,” IEEE J. Sel. Top. Quantum Electron. 13(2), 162–167 (2007). [CrossRef]

18.

R. Hokari and K. Hane, “A varifocal convex micromirror driven by a bending moment,” IEEE J. Sel. Top. Quantum Electron. 15(5), 1310–1316 (2009). [CrossRef]

19.

T.Wu, K.Hane, “High-precise spherical micromirror by bending silicon plate with metal pad,” (to be published).

20.

V. Dragoi, P. Lindner, T. Glinsner, M. Wimplinger, and S. Farrens, “Advanced Anodic Bonding Processes for MEMS Applications,” in Proceedings of Materials Research Society Symposium (Materials Research Society, 2004), 782, pp.A5.80.1–6.

OCIS Codes
(220.4000) Optical design and fabrication : Microstructure fabrication
(230.3990) Optical devices : Micro-optical devices

ToC Category:
Optical Design and Fabrication

History
Original Manuscript: February 22, 2011
Revised Manuscript: May 27, 2011
Manuscript Accepted: May 30, 2011
Published: June 3, 2011

Citation
Tong Wu, Takahiro Yamasaki, Ryohei Hokari, and Kazuhiro Hane, "Spherical silicon micromirrors bent by anodic bonding," Opt. Express 19, 11897-11905 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-12-11897


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References

  1. H. P. Herzig, Micro-optics (Taylor&Francis, 1997).
  2. S. Audran, B. Faure, B. Mortini, J. Regolini, G. Schlatter, and G. Hadziioannou, “Study of mechanisms involved in photoresist microlens formation,” Microelectron. Eng. 83(4-9), 1087–1090 (2006). [CrossRef]
  3. G. Wang, S. Wang, and C.-H. Chin, “Fabrication and molding of gray-scale mask based aspheric refraction micro-lens array,” JSME Int. J., Ser. C 46(4), 1598–1603 (2003). [CrossRef]
  4. K. Totsu and M. Esashi, “Gray-scale photolithography using maskless exposure system,” J. Vac. Sci. Technol. B 23(4), 1487–1490 (2005). [CrossRef]
  5. T.-W. Lin, C.-F. Chen, J.-J. Yang, and Y.-S. Liao, “A dual-directional light-control film with a high-sag and high-asymmetrical-shape microlens array fabricated by a UV imprinting process,” J. Micromech. Microeng. 18(9), 095029 (2008). [CrossRef]
  6. Y. Kanamori, J. Sato, T. Shimano, S. Nakamura, and K. Hane, “Polymer microstructure generated by laser stereo-lithography and its transfer to silicon substrate using reactive ion etching,” Microsyst. Technol. 13(8-10), 1411–1416 (2007). [CrossRef]
  7. S. Biehl, R. Danzebrink, P. Oliveira, and M. A. Aegerter, “Refractive Microlens Fabrication by Ink-Jet Process,” J. Sol-Gel Sci. Technol. 13(1/3), 177–182 (1998). [CrossRef]
  8. C.-T. Chen, Z.-F. Tseng, C.-L. Chiu, C.-Y. Hsu, and C.-T. Chuang, “Self-aligned hemispherical formation of microlenses from colloidal droplets on heterogeneous surfaces,” J. Micromech. Microeng. 19(2), 025002 (2009). [CrossRef]
  9. S. Lee, Y.-C. Jeong, and J.-K. Park, “Facile fabrication of close-packed microlens arrays using photoinduced surface relief structures as templates,” Opt. Express 15(22), 14550–14559 (2007). [CrossRef] [PubMed]
  10. S.- Moon, N. Lee, and S. Kang, “Fabrication of a microlens array using micro-compression molding with an electroformed mold insert,” J. Micromech. Microeng. 13(1), 98–103 (2003). [CrossRef]
  11. G. C. Firestone and A. Y. Yi, “Precision compression molding of glass microlenses and microlens arrays--an experimental study,” Appl. Opt. 44(29), 6115–6122 (2005). [CrossRef] [PubMed]
  12. P. Merz, H. J. Quenzer, H. Bernt, B. Wagner, and M. Zoberbier, “A novel micromachining technology for structuring borosilicate glass substrates,” in Proceedings of IEEE Conference on Solid State Sensors, Actuators and Microsystems (IEEE, 2003), pp.258–261.
  13. J.-T. Wu, W.-Y. Chang, and S.-Y. Yang, “Fabrication of a nano/micro hybrid lens using gas-assisted hot embossing with an anodic aluminum oxide (AAO) template,” J. Micromech. Microeng. 20(7), 075023 (2010). [CrossRef]
  14. L. Wu, S. Dooley, E. A. Watson, P. F. McManamon, and H. Xie, “A Tip-Tilt-Piston Micromirror Array for Optical Phased Array Applications,” J. Microelectromech. Syst. 19(6), 1450–1461 (2010). [CrossRef]
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