Abstract

We present a simple method to fabricate blazed gratings used in the extreme-ultraviolet wavelength region. The method uses an argon and oxygen ion beam to etch directly the fused silica substrate through a rectangular profile photoresist grating mask. The blaze angle can be significantly reduced by using oxygen, and the profile evolution under ion-beam bombardment can be simplified when a rectangular mask is used. A simple geometric model is built to analyze the etching process. The etched grating groove profile is approximately triangular with a sharp apex angle provided the aspect ratio of the mask ridge is properly chosen; the blaze angle is directly proportional to the ion-beam grazing incident angle for a fixed oxygen partial pressure. Gratings of a 2400  line/mm groove density and 0.53° blaze angles have been fabricated, which confirms the convenience of this method and the effectiveness of the etching model.

© 2008 Optical Society of America

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References

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  1. M. C. Hutley, Diffraction Gratings (Academic, 1982).
  2. Y. Aoyagi and S. Namba, “Blazed ion-etched holographic gratings,” Opt. Acta 23, 701-707 (1976).
    [CrossRef]
  3. B. Nelles, K. F. Heidemann, and B. Kleemann, “Design, manufacturing and testing of gratings for synchrotron radiation,” Nucl. Instrum. Methods Phys. Res. A 467-468, 260-266(2001).
    [CrossRef]
  4. K. Osterried, K. F. Heidemann, and B. Nelles, “Groove profile modification of blazed gratings by dip coating with hardenable liquids,” Appl. Opt. 37, 8002-8007 (1998).
    [CrossRef]
  5. B. de A. Mello, I. F. da Costa, C. R. A. Lima, and L. Cescato, “Developed profile of holographically exposed photoresist gratings,” Appl. Opt. 34, 597-603 (1995).
    [CrossRef]
  6. L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for sub-micrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1988).
  7. G. Aston, H. R. Kaufman, and P. J. Wilbur, “Ion beam divergence characteristics of two-grid accelerator systems,” AIAA J. 16, 516-524 (1978).
    [CrossRef]
  8. M. P. Kowalski, W. R. Hunter, and T. W. Barbee, Jr., “Replication of a holographic ion-etched spherical blazed grating for use at extreme-ultraviolet wavelengths: topography,” Appl. Opt. 45, 305-321 (2006).
    [CrossRef] [PubMed]
  9. L. F. Johnson, “Evolution of grating profiles under ion-beam erosion,” Appl. Opt. 18, 2559-2574 (1979).
    [CrossRef] [PubMed]
  10. S. Somekh, “Introduction to ion and plasma etching,” J. Vac. Sci. Technol. 13, 1003-1007 (1976).
    [CrossRef]
  11. H. Lin, L. Zhang, L. Li, C. Jin, H. Zhou, and T. Huo, “High-efficiency multilayer-coated ion-beam-etched blazed grating in the extreme-ultraviolet wavelength region,” Opt. Lett. 33, 485-487 (2008).
    [CrossRef] [PubMed]

2008

2006

2001

B. Nelles, K. F. Heidemann, and B. Kleemann, “Design, manufacturing and testing of gratings for synchrotron radiation,” Nucl. Instrum. Methods Phys. Res. A 467-468, 260-266(2001).
[CrossRef]

1998

1995

1988

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for sub-micrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1988).

1979

1978

G. Aston, H. R. Kaufman, and P. J. Wilbur, “Ion beam divergence characteristics of two-grid accelerator systems,” AIAA J. 16, 516-524 (1978).
[CrossRef]

1976

S. Somekh, “Introduction to ion and plasma etching,” J. Vac. Sci. Technol. 13, 1003-1007 (1976).
[CrossRef]

Y. Aoyagi and S. Namba, “Blazed ion-etched holographic gratings,” Opt. Acta 23, 701-707 (1976).
[CrossRef]

Aoyagi, Y.

Y. Aoyagi and S. Namba, “Blazed ion-etched holographic gratings,” Opt. Acta 23, 701-707 (1976).
[CrossRef]

Aston, G.

G. Aston, H. R. Kaufman, and P. J. Wilbur, “Ion beam divergence characteristics of two-grid accelerator systems,” AIAA J. 16, 516-524 (1978).
[CrossRef]

Barbee, T. W.

Cescato, L.

da Costa, I. F.

Heidemann, K. F.

B. Nelles, K. F. Heidemann, and B. Kleemann, “Design, manufacturing and testing of gratings for synchrotron radiation,” Nucl. Instrum. Methods Phys. Res. A 467-468, 260-266(2001).
[CrossRef]

K. Osterried, K. F. Heidemann, and B. Nelles, “Groove profile modification of blazed gratings by dip coating with hardenable liquids,” Appl. Opt. 37, 8002-8007 (1998).
[CrossRef]

Hunter, W. R.

Huo, T.

Hutley, M. C.

M. C. Hutley, Diffraction Gratings (Academic, 1982).

Jin, C.

Johnson, L. F.

Kaufman, H. R.

G. Aston, H. R. Kaufman, and P. J. Wilbur, “Ion beam divergence characteristics of two-grid accelerator systems,” AIAA J. 16, 516-524 (1978).
[CrossRef]

Kleemann, B.

B. Nelles, K. F. Heidemann, and B. Kleemann, “Design, manufacturing and testing of gratings for synchrotron radiation,” Nucl. Instrum. Methods Phys. Res. A 467-468, 260-266(2001).
[CrossRef]

Kowalski, M. P.

Li, L.

H. Lin, L. Zhang, L. Li, C. Jin, H. Zhou, and T. Huo, “High-efficiency multilayer-coated ion-beam-etched blazed grating in the extreme-ultraviolet wavelength region,” Opt. Lett. 33, 485-487 (2008).
[CrossRef] [PubMed]

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for sub-micrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1988).

Lima, C. R. A.

Lin, H.

Mello, B. de A.

Namba, S.

Y. Aoyagi and S. Namba, “Blazed ion-etched holographic gratings,” Opt. Acta 23, 701-707 (1976).
[CrossRef]

Nelles, B.

B. Nelles, K. F. Heidemann, and B. Kleemann, “Design, manufacturing and testing of gratings for synchrotron radiation,” Nucl. Instrum. Methods Phys. Res. A 467-468, 260-266(2001).
[CrossRef]

K. Osterried, K. F. Heidemann, and B. Nelles, “Groove profile modification of blazed gratings by dip coating with hardenable liquids,” Appl. Opt. 37, 8002-8007 (1998).
[CrossRef]

Osterried, K.

Seaton, C. T.

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for sub-micrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1988).

Somekh, S.

S. Somekh, “Introduction to ion and plasma etching,” J. Vac. Sci. Technol. 13, 1003-1007 (1976).
[CrossRef]

Stegeman, G. I.

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for sub-micrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1988).

Wilbur, P. J.

G. Aston, H. R. Kaufman, and P. J. Wilbur, “Ion beam divergence characteristics of two-grid accelerator systems,” AIAA J. 16, 516-524 (1978).
[CrossRef]

Xu, M.

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for sub-micrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1988).

Zhang, L.

Zhou, H.

AIAA J.

G. Aston, H. R. Kaufman, and P. J. Wilbur, “Ion beam divergence characteristics of two-grid accelerator systems,” AIAA J. 16, 516-524 (1978).
[CrossRef]

Appl. Opt.

J. Vac. Sci. Technol.

S. Somekh, “Introduction to ion and plasma etching,” J. Vac. Sci. Technol. 13, 1003-1007 (1976).
[CrossRef]

Nucl. Instrum. Methods Phys. Res. A

B. Nelles, K. F. Heidemann, and B. Kleemann, “Design, manufacturing and testing of gratings for synchrotron radiation,” Nucl. Instrum. Methods Phys. Res. A 467-468, 260-266(2001).
[CrossRef]

Opt. Acta

Y. Aoyagi and S. Namba, “Blazed ion-etched holographic gratings,” Opt. Acta 23, 701-707 (1976).
[CrossRef]

Opt. Lett.

Proc. SPIE

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for sub-micrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1988).

Other

M. C. Hutley, Diffraction Gratings (Academic, 1982).

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Figures (8)

Fig. 1
Fig. 1

Schematic diagram of the experimental configuration for ion-beam etching.

Fig. 2
Fig. 2

SEM images of the grating profile evolution under ion-beam etching: (a) photoresist mask before etching; mask etched for (b) 1 min, (c) 2 min, (d) 3 min. In (d) the photoresist was thoroughly removed.

Fig. 3
Fig. 3

Diagram of the ion-beam etching process. (a) When h > h c , the mask is etched and the substrate is sheltered from the ion beam. (b) When h < h c , both the mask and the substrate are etched.

Fig. 4
Fig. 4

Relationship between the optimum ridge aspect ratio Γ o and the ion-beam grazing incident angle φ.

Fig. 5
Fig. 5

Profiles of three gratings etched through masks with different ridge aspect ratios Γ: (a)  Γ = Γ o = 0.5 (the optimum Γ at φ = 6 ° ); (b)  Γ = 0.35 ; (c)  Γ = 0.9 .

Fig. 6
Fig. 6

Profiles of three gratings etched through masks with the same ridge aspect ratio Γ ( Γ = Γ o = 0.5 at φ = 6 ° ) but different ridge height h 0 : (a)  h 0 45 nm ; (b)  h 0 70 nm ; (c)  h 0 90 nm .

Fig. 7
Fig. 7

Experimentally measured blaze angle β at different ion-beam grazing incident angles φ and O 2 partial pressures P O .

Fig. 8
Fig. 8

Profiles of two gratings etched at different ion-beam grazing incident angles φ: (a)  φ = 4 ° and (b)  φ = 6 ° .

Equations (5)

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Γ o = h 0 w 0 = V P h V P w * .
V l = V S sin β = V P h tan φ .
V S = V S φ ( φ - β ) ,
V P h = V P φ φ ,
β = 1 1 + V P φ / V S φ φ = k φ ,

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