Abstract

This study compares and quantifies the simulated effects of noise, index errors, and photometric level errors on different optical monitoring layer termination strategies. A computer program to simulate optical thin film monitoring has been written for this work. The study looked at these termination methods: quartz crystal monitoring, photometric level cut, two types of turning point termination, and percent of optical extrema monitoring. A narrow bandpass filter and a four-layer antireflection coating design were simulated as examples.

© 2013 Optical Society of America

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References

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  1. R. R. Willey, A. Zöller, “Computer simulation of monitoring of narrow bandpass filters at non-turning points,” 52nd Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2009), pp. 432–437.
  2. R. R. Willey, S. Hicks, M. Biagi, “Analysis of optical monitoring strategies for narrow bandpass filters by software simulation,” 55th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2012), pp. 253–257.
  3. FilmStar Design from FTG Software Associates, P. O. Box 579, Princeton, New Jersey 08542.
  4. C. Schroedter, “Evaporation monitoring system featuring software trigger points and online evaluation of refractive indices,” Proc. SPIE 652, 15–20 (1986).
    [CrossRef]
  5. R. R. Willey, “Simulation of the percentage of optical extrema monitoring,” in 56th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2013).

1986 (1)

C. Schroedter, “Evaporation monitoring system featuring software trigger points and online evaluation of refractive indices,” Proc. SPIE 652, 15–20 (1986).
[CrossRef]

Biagi, M.

R. R. Willey, S. Hicks, M. Biagi, “Analysis of optical monitoring strategies for narrow bandpass filters by software simulation,” 55th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2012), pp. 253–257.

Hicks, S.

R. R. Willey, S. Hicks, M. Biagi, “Analysis of optical monitoring strategies for narrow bandpass filters by software simulation,” 55th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2012), pp. 253–257.

Schroedter, C.

C. Schroedter, “Evaporation monitoring system featuring software trigger points and online evaluation of refractive indices,” Proc. SPIE 652, 15–20 (1986).
[CrossRef]

Willey, R. R.

R. R. Willey, S. Hicks, M. Biagi, “Analysis of optical monitoring strategies for narrow bandpass filters by software simulation,” 55th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2012), pp. 253–257.

R. R. Willey, A. Zöller, “Computer simulation of monitoring of narrow bandpass filters at non-turning points,” 52nd Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2009), pp. 432–437.

R. R. Willey, “Simulation of the percentage of optical extrema monitoring,” in 56th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2013).

Zöller, A.

R. R. Willey, A. Zöller, “Computer simulation of monitoring of narrow bandpass filters at non-turning points,” 52nd Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2009), pp. 432–437.

Proc. SPIE (1)

C. Schroedter, “Evaporation monitoring system featuring software trigger points and online evaluation of refractive indices,” Proc. SPIE 652, 15–20 (1986).
[CrossRef]

Other (4)

R. R. Willey, “Simulation of the percentage of optical extrema monitoring,” in 56th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2013).

R. R. Willey, A. Zöller, “Computer simulation of monitoring of narrow bandpass filters at non-turning points,” 52nd Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2009), pp. 432–437.

R. R. Willey, S. Hicks, M. Biagi, “Analysis of optical monitoring strategies for narrow bandpass filters by software simulation,” 55th Annual Technical Conference Proceedings (Society of Vacuum Coaters, 2012), pp. 253–257.

FilmStar Design from FTG Software Associates, P. O. Box 579, Princeton, New Jersey 08542.

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Figures (14)

Fig. 1.
Fig. 1.

Computer-simulated monitoring curve of %R versus physical thickness monitoring at 380 nm in reflectance for the four-layer AR.

Fig. 2.
Fig. 2.

Physical thickness error as a function of index of refraction variations and photometric scale error when using the LEVEL CUT strategy with a 3 PE between extrema and an optical monitor noise at ± 0.2 % .

Fig. 3.
Fig. 3.

Typical raw optical monitor signal with ± 0.3 % noise. Inset is a 7 × expansion of the region around the TP with 0.3% vertical chart intervals to illustrate the scope of the noise.

Fig. 4.
Fig. 4.

Five points method illustrated indicates a TP when the last point monitored shows a change in direction from the first three points of the most recent five points in succession.

Fig. 5.
Fig. 5.

Parabolic curve matches the sine curve in the region of a TP. The b and c constants define the position of the vertex of the parabola (TP) with respect to the origin. A LC is also illustrated at a specified photometric level.

Fig. 6.
Fig. 6.

In the presence of some noise, if three data points are taken in a close grouping at some great distance before the TP is reached the predicted TP is likely to be greatly in error. If the three points are widely spaced in X the prediction will be much more accurate.

Fig. 7.
Fig. 7.

Three different runs of the predicted TP with each new data point as it is calculated, with a monitor noise of ± 0.1 % . Line with zero noise is included.

Fig. 8.
Fig. 8.

Systematic physical thickness errors in nanometers versus cut point position (PE) with ± 0.1 % noise using the four different termination strategies.

Fig. 9.
Fig. 9.

Standard deviation of the PT error in nanometers from the data runs in Fig. 8 versus cut point position with ± 0.1 % noise.

Fig. 10.
Fig. 10.

Monitoring trace simulation showing: (a) regular 2 1 design which is cut at TPs, (b) changed to 3 1 , and (c) adjusted 3 1 design so that all even layers are cut with a PE of 15%. All cases are monitored at the passband wavelength.

Fig. 11.
Fig. 11.

(a) POEM where the cut point is 5% down from that last extremum in designs of the type in Fig. 10(c); (b), (c) similar to (a) except for 10% and 15% from the extrema; (d) P-Fit strategy to detect a TP; and (e) five-point method.

Fig. 12.
Fig. 12.

(a)–(e) Similar to Figs. 11(a)11(e) on a narrower band with ± 0.7 % noise in the OM signal.

Fig. 13.
Fig. 13.

Simulated optical monitor signal for this four-layer BBAR at each of the wavelengths studied from 380 to 800 nm.

Fig. 14.
Fig. 14.

Results of 10 simulated runs each, with random noise at the single monitoring wavelengths from 380 to 800 nm. Shows the best strategies for each layer (i.e., 4112) at that monitoring wavelength and the percentage noise (on the right) just before a BD. Layer Monitoring Type Codes: 1 = POEM , 2 = TP P-Fit, 3 = TP five-point, and 4 = Crystal .

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