Abstract

Multilayer coatings on large substrates with increasingly complex spectral requirements are essential for a number of optical systems, placing stringent requirements on the error tolerances of individual layers. Each layer must be deposited quite uniformly over the entire substrate surface since any nonuniformity will add to the layer-thickness error level achieved. A deposition system containing a planetary rotation system with stationary uniformity masking is modeled, with refinements of the planetary gearing, source placement, and uniformity mask shape being utilized to achieve an optimal configuration. The impact of improper planetary gearing is demonstrated theoretically, as well as experimentally, providing more comprehensive requirements than simply avoiding repetition of previous paths through the vapor plume, until all possible combinations of gear teeth have been used. Deposition efficiency and the impact of changing vapor plume conditions on the uniformity achieved are used to validate improved source placement. Uniformity measurements performed on a mapping laser photometer demonstrate nonuniformities of less than 0.5% for 0.75  m optics in a 72  in.(1.8m) coating chamber.

© 2006 Optical Society of America

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References

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  1. I. C. Stevenson and G. Sadkhin, "Optimum location of the evaporation source: experimental verification," in Proceedings of the 44th Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 2001), pp. 306-313.
  2. D. J. Smith, A. Staley, R. Eriksson, and G. Algar, "Counter-rotating planetary design for large rectangular substrates," in Proceedings of the 41st Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 1998), pp. 193-196.
  3. B. Andre, L. Poupinet, and G. Ravel, "Evaporation and ion assisted deposition of HfO2 coatings: some key points for high power laser applications," J. Vac. Sci. Technol. A 18, 2372-2377 (2000).
    [CrossRef]
  4. R. Chow, S. Falabella, G. E. Loomis, F. Rainer, C. J. Stolz, and M. R. Kozlowski, "Reactive evaporation of low-defect density hafnia," Appl. Opt. 32, 5567-5574 (1993).
    [CrossRef] [PubMed]
  5. B. S. Ramprasad and T. S. Radha, "Uniformity of film thickness on rotating planetary planar substrates," Thin Solid Films 15, 55-64 (1973).
    [CrossRef]
  6. K. H. Behrndt, "Thickness uniformity on rotating substrates," in Transactions of the Tenth National Vacuum Symposium of the American Vacuum Society, G.H.Bancroft, ed. (Macmillan, 1963), pp. 379-384.
  7. A. G. Zhiglinskiy and E. S. Putilin, "Optimal conditions for depositing uniform thin films," Opt. Technol. 38, 557-559 (1971).
  8. H. A. Macleod, Thin-Film Optical Filters, 3rd ed. (Institute of Physics, 2001), pp. 488-497.
    [CrossRef]
  9. A. Musset and I. C. Stevenson, "Obtaining uniformly thick films in coating chambers," in Proceedings of the 31st Annual Technical Conference of the Society of Vacuum Coaters. (Society of Vacuum Coaters, 1988), pp. 203-209.

2000 (1)

B. Andre, L. Poupinet, and G. Ravel, "Evaporation and ion assisted deposition of HfO2 coatings: some key points for high power laser applications," J. Vac. Sci. Technol. A 18, 2372-2377 (2000).
[CrossRef]

1993 (1)

1973 (1)

B. S. Ramprasad and T. S. Radha, "Uniformity of film thickness on rotating planetary planar substrates," Thin Solid Films 15, 55-64 (1973).
[CrossRef]

1971 (1)

A. G. Zhiglinskiy and E. S. Putilin, "Optimal conditions for depositing uniform thin films," Opt. Technol. 38, 557-559 (1971).

Algar, G.

D. J. Smith, A. Staley, R. Eriksson, and G. Algar, "Counter-rotating planetary design for large rectangular substrates," in Proceedings of the 41st Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 1998), pp. 193-196.

Andre, B.

B. Andre, L. Poupinet, and G. Ravel, "Evaporation and ion assisted deposition of HfO2 coatings: some key points for high power laser applications," J. Vac. Sci. Technol. A 18, 2372-2377 (2000).
[CrossRef]

Behrndt, K. H.

K. H. Behrndt, "Thickness uniformity on rotating substrates," in Transactions of the Tenth National Vacuum Symposium of the American Vacuum Society, G.H.Bancroft, ed. (Macmillan, 1963), pp. 379-384.

Chow, R.

Eriksson, R.

D. J. Smith, A. Staley, R. Eriksson, and G. Algar, "Counter-rotating planetary design for large rectangular substrates," in Proceedings of the 41st Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 1998), pp. 193-196.

Falabella, S.

Kozlowski, M. R.

Loomis, G. E.

Macleod, H. A.

H. A. Macleod, Thin-Film Optical Filters, 3rd ed. (Institute of Physics, 2001), pp. 488-497.
[CrossRef]

Musset, A.

A. Musset and I. C. Stevenson, "Obtaining uniformly thick films in coating chambers," in Proceedings of the 31st Annual Technical Conference of the Society of Vacuum Coaters. (Society of Vacuum Coaters, 1988), pp. 203-209.

Poupinet, L.

B. Andre, L. Poupinet, and G. Ravel, "Evaporation and ion assisted deposition of HfO2 coatings: some key points for high power laser applications," J. Vac. Sci. Technol. A 18, 2372-2377 (2000).
[CrossRef]

Putilin, E. S.

A. G. Zhiglinskiy and E. S. Putilin, "Optimal conditions for depositing uniform thin films," Opt. Technol. 38, 557-559 (1971).

Radha, T. S.

B. S. Ramprasad and T. S. Radha, "Uniformity of film thickness on rotating planetary planar substrates," Thin Solid Films 15, 55-64 (1973).
[CrossRef]

Rainer, F.

Ramprasad, B. S.

B. S. Ramprasad and T. S. Radha, "Uniformity of film thickness on rotating planetary planar substrates," Thin Solid Films 15, 55-64 (1973).
[CrossRef]

Ravel, G.

B. Andre, L. Poupinet, and G. Ravel, "Evaporation and ion assisted deposition of HfO2 coatings: some key points for high power laser applications," J. Vac. Sci. Technol. A 18, 2372-2377 (2000).
[CrossRef]

Sadkhin, G.

I. C. Stevenson and G. Sadkhin, "Optimum location of the evaporation source: experimental verification," in Proceedings of the 44th Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 2001), pp. 306-313.

Smith, D. J.

D. J. Smith, A. Staley, R. Eriksson, and G. Algar, "Counter-rotating planetary design for large rectangular substrates," in Proceedings of the 41st Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 1998), pp. 193-196.

Staley, A.

D. J. Smith, A. Staley, R. Eriksson, and G. Algar, "Counter-rotating planetary design for large rectangular substrates," in Proceedings of the 41st Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 1998), pp. 193-196.

Stevenson, I. C.

A. Musset and I. C. Stevenson, "Obtaining uniformly thick films in coating chambers," in Proceedings of the 31st Annual Technical Conference of the Society of Vacuum Coaters. (Society of Vacuum Coaters, 1988), pp. 203-209.

I. C. Stevenson and G. Sadkhin, "Optimum location of the evaporation source: experimental verification," in Proceedings of the 44th Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 2001), pp. 306-313.

Stolz, C. J.

Zhiglinskiy, A. G.

A. G. Zhiglinskiy and E. S. Putilin, "Optimal conditions for depositing uniform thin films," Opt. Technol. 38, 557-559 (1971).

Appl. Opt. (1)

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

B. Andre, L. Poupinet, and G. Ravel, "Evaporation and ion assisted deposition of HfO2 coatings: some key points for high power laser applications," J. Vac. Sci. Technol. A 18, 2372-2377 (2000).
[CrossRef]

Opt. Technol. (1)

A. G. Zhiglinskiy and E. S. Putilin, "Optimal conditions for depositing uniform thin films," Opt. Technol. 38, 557-559 (1971).

Thin Solid Films (1)

B. S. Ramprasad and T. S. Radha, "Uniformity of film thickness on rotating planetary planar substrates," Thin Solid Films 15, 55-64 (1973).
[CrossRef]

Other (5)

K. H. Behrndt, "Thickness uniformity on rotating substrates," in Transactions of the Tenth National Vacuum Symposium of the American Vacuum Society, G.H.Bancroft, ed. (Macmillan, 1963), pp. 379-384.

I. C. Stevenson and G. Sadkhin, "Optimum location of the evaporation source: experimental verification," in Proceedings of the 44th Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 2001), pp. 306-313.

D. J. Smith, A. Staley, R. Eriksson, and G. Algar, "Counter-rotating planetary design for large rectangular substrates," in Proceedings of the 41st Annual Technical Conference of the Society of Vacuum Coaters (Society of Vacuum Coaters, 1998), pp. 193-196.

H. A. Macleod, Thin-Film Optical Filters, 3rd ed. (Institute of Physics, 2001), pp. 488-497.
[CrossRef]

A. Musset and I. C. Stevenson, "Obtaining uniformly thick films in coating chambers," in Proceedings of the 31st Annual Technical Conference of the Society of Vacuum Coaters. (Society of Vacuum Coaters, 1988), pp. 203-209.

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Figures (12)

Fig. 1
Fig. 1

Basic planetary configuration as substrate undergoes rotations∕revolution.

Fig. 2
Fig. 2

Deposition efficiency is calculated by transforming the source location to a position on-axis with the rotation and integrating over the maximum area described by the planetary motion, a disk with radius R + ρmax.

Fig. 3
Fig. 3

Efficiency of material utilization as a function of the offset of the source from the center of the coating chamber. An offset of 0 is for source location (0, 0, zs ) in Fig. 1, with increasing offsets representing the movement of the source along the x axis. While there is a significant reduction in the efficiency of the material being evaporated, the reduction in the size of secondary masking will reduce this loss.

Fig. 4
Fig. 4

Scanning laser photometer at the LLE. This system is capable of simultaneously measuring % T and % R over a 525 mm × 807 mm aperture, from 8° to 60°, at wavelengths of 1053, 527, and 351 nm. Results are presented as a two-dimensional intensity map of the surface, digitized to pixels of 1 to 5 mm.

Fig. 5
Fig. 5

Modified quarter-wave reflector with linear transmission with respect to wavelength over the range λ0 ± 2%. Provided the coating is deposited properly and all nonuniformities are less than 4% peak-to-valley, the resulting photometer transmittance map will directly correlate to film-thickness uniformity.

Fig. 6
Fig. 6

Cycloids traced out by an off-center point in a planetary rotation after one revolution with different integral gear ratios. Note that all figures are closed, requiring that the point will trace out an identical path for all successive revolutions.

Fig. 7
Fig. 7

Relative planet orientations versus revolutions of the planetary rotation. Every three revolutions, the planet assumes almost the same angular orientation, differing only by 5.1°.

Fig. 8
Fig. 8

Comparison of the effects of different planetary gear ratios. The graphs in Row I track the angular orientation of a planet each time it passes a fixed point in the chamber, such as the center of the door, as a function of the number of revolutions of the planetary. Since a geared system is being analyzed, the possible angles correspond to a specific gear tooth number. Row II depicts the path of an off-center planetary point through 30 revolutions of the planetary. Row III depicts the measured film uniformity pattern on the mapping laser photometer. Gearing configuration (c) provides a greater degree of randomization through the vapor plume, yielding significant improvements in film uniformity.

Fig. 9
Fig. 9

Mask configuration implemented in a 72 in. (1.8 m) coating chamber for a counterrotating planetary. Multipoint quartz crystal monitoring is installed in the mask mounts, providing six thickness∕rate measurements.

Fig. 10
Fig. 10

Theoretical uniformity of film deposition over the radius of the planet versus offset of the source position from the center of the coating chamber for zp zs = 1200 mm, R = 391 mm, and n = 1.6. By minimizing the nonuniformity of the deposited film, the degree of secondary masking will also be minimized.

Fig. 11
Fig. 11

Theoretical influence of source offset on the sensitivity of film uniformity to changes in the vapor plume distribution. Source distribution modeled as cos1.6 θ, with n varying ±0.2. Two significantly different mask designs are modeled, each with two source offsets, showing that the greater source offset is actually less sensitive to variations in the vapor plume. At left, E-guns at 30 in. (76 cm); at right, E-guns at 25 in. (64 cm).

Fig. 12
Fig. 12

Film nonuniformity in both the counterrotating and forward-rotating planets for a masked configuration with electron-beam sources at 76 cm offset from chamber center. Roll-off is evident along the edge of the coating due to shadowing effects of the coating tooling. Discounting this effect, which may be eliminated by modification of the coating tooling, both uniformity maps exhibit 0.45% nonuniformity peak-to-valley. Furthermore, if the tilt evident in both surface plots is subtracted, since this is a result of the optic rotating out-of-plane, nonuniformity is reduced to 0.30%.

Equations (15)

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t = ( m π μ ) ( cos ϕ cos θ r 2 ) ,
t = cos ϕ cos θ r 2 .
t = cos 2 θ r 2 .
t = cos n θ r 2 ,
r = ( x p x s ) 2 + ( y p y s ) 2 + ( z p z s ) 2 ,
cos θ = z p z s ( x p x s ) 2 + ( y p y s ) 2 + ( z p z s ) 2 ,
t = { ( z p z s ) n [ ( x p x s ) 2 + ( y p y s ) 2 + ( z p z s ) 2 ] ( n + 2 ) / 2 } .
x ( α ) = R cos α + ρ cos ( α N s N p ) ,
y ( α ) = R sin α + ρ sin ( α N s N p ) ,
efficiency = 1 π over disk cos n + 1 θ r 2  d γ d θ .
efficiency =
1 π 0 2 π 0 R + ρ max h n + 1 r d r d γ [ r 2 + 2 r D cos γ + h 2 + D 2 ] ( n + 3 ) / 2 ,
gear ratio = N s N p .
m ( N s N p ) = an integer , m = 1 , 2 , 3 ,
m = N p g ,

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