Abstract

A technique for controlling the thickness profile of a thin film in physical vapor deposition systems is reported. The technique uses a novel mask design with apertures of varying dimension to selectively deposit the required film thickness at predetermined locations across the aperture of the substrate. The technique has been used to correct the thickness uniformity of a 55 mm diameter, 280 µm thick, lithium niobate wafer to less than 0.5 nm rms, and also to improve the uniformity of deposited films in an Ion Beam Sputtering system to better than 0.5% over a 50 mm aperture.

© 2005 Optical Society of America

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References

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  1. P. W. Baumeister, Optical Coating Technology (SPIE Press, Washington, 2004), Chapter 9 and references therein.
    [CrossRef]
  2. J. R. Kurdock and R. R. Austin, �??Correction of Optical Elements by the Addition of Evaporated Films,�?? Physics of Thin Films, Academic Press, (1978).
  3. J. M. Mackowski, L. Pinard, L. Dognin, P. Ganau, B. Lagrange, C. Michel, M. Morgue, �??Different approaches to improve the wavefront of low-loss mirrors used in the Virgo gravitational wave antenna,�?? Applied Surface Science 86-90 (1999).
    [CrossRef]
  4. C. D. Prasad, S. K. Mathew, A. Bhatnagar, A Ambastha, �??Solar photospheric and chromospheric observations using a lithium niobate Fabry-Perot etalon,�?? Experimental Astronomy 125-133, (1998).
    [CrossRef]
  5. A. J. Leistner, �??Teflon polishers: their manufacture and use,�?? Applied Optics 293, (1976).
  6. J. A. Seckold, �??Precision flat polishing of lithium niobate,�?? Optical Fabrication and Testing OSA Technical Digest Series Optical Society of America, Washington, D. C. (1996).
  7. P. S. Fairman, D. I. Farrant, and J. W. Arkwright, CSIRO Industrial Physics are preparing a manuscript to be called �??High resolution metrology of high-finesse Fabry Perot structures�??.

Applied Optics

A. J. Leistner, �??Teflon polishers: their manufacture and use,�?? Applied Optics 293, (1976).

Applied Surface Science

J. M. Mackowski, L. Pinard, L. Dognin, P. Ganau, B. Lagrange, C. Michel, M. Morgue, �??Different approaches to improve the wavefront of low-loss mirrors used in the Virgo gravitational wave antenna,�?? Applied Surface Science 86-90 (1999).
[CrossRef]

Experimental Astronomy

C. D. Prasad, S. K. Mathew, A. Bhatnagar, A Ambastha, �??Solar photospheric and chromospheric observations using a lithium niobate Fabry-Perot etalon,�?? Experimental Astronomy 125-133, (1998).
[CrossRef]

Optical Fabrication and Testing 1996

J. A. Seckold, �??Precision flat polishing of lithium niobate,�?? Optical Fabrication and Testing OSA Technical Digest Series Optical Society of America, Washington, D. C. (1996).

Other

P. S. Fairman, D. I. Farrant, and J. W. Arkwright, CSIRO Industrial Physics are preparing a manuscript to be called �??High resolution metrology of high-finesse Fabry Perot structures�??.

P. W. Baumeister, Optical Coating Technology (SPIE Press, Washington, 2004), Chapter 9 and references therein.
[CrossRef]

J. R. Kurdock and R. R. Austin, �??Correction of Optical Elements by the Addition of Evaporated Films,�?? Physics of Thin Films, Academic Press, (1978).

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Figures (11)

Fig. 1.
Fig. 1.

(a) Schematic of a 60×60 mm aperture mask used to apply a ramped thickness profile to a deposited thin film. (b) Detail of the aperture distribution showing the direction and amplitude of applied dither.

Fig. 2.
Fig. 2.

Location of the aperture mask with respect to the deposition source and substrate in the IBS machine.

Fig. 3.
Fig. 3.

Effect of the finite sized target and offset between aperture mask and substrate.

Fig. 4.
Fig. 4.

Results of the deposition rate trials carried out using a) no mask, b) a uniform mask, and c) a ramped mask.

Fig. 5.
Fig. 5.

Measured thickness profiles of the deposited films; a) along the horizontal axis; and b) along the vertical axis.

Fig. 6.
Fig. 6.

Measured thickness variation of a 55 mm diameter 280 µm thick lithium niobate wafer before correction.

Fig. 7.
Fig. 7.

Schematic of the aperture mask used to correct the wafer shown in Fig. 6.

Fig. 8.
Fig. 8.

Measured thickness variation of the wafer shown in Fig. 6 after correction.

Fig. 9.
Fig. 9.

Horizontal and Vertical thickness variation profiles of the wafer shown in Fig. 8.

Fig. 10.
Fig. 10.

Thickness variation of the wafer in Fig. 6 after the large scale variations have been removed using a 2D polynomial fit to the surface

Fig. 11.
Fig. 11.

Measured horizontal thickness variation across the centre of the wafer shown in Fig. 8: a) before and b) after correction (with large scale variations removed).

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