Experimental Results
| No. | Film sample | Geom, thickness h (μm) | dc (Ref. 5) (μm) | Frac (h/dc) | n = tanθB (min) | n (From Refs.) |
|---|
| 1 | Photoresist KMR-747 | 1.10 | 0.244 | 0.51 | 1.546 ± 0.001 (±1) | 1.556 |
| 2 | Photoresist KMR-747 | 0.26 | 0.244 | 0.07 | … | 1.556 |
| 3 | Photoresist KTFR | 3.20 | 0.243 | 0.17 | 1.55 ± 0.01 (±10) | 1.5417 |
| 4 | Photoresist AZ-111 | 0.73 | 0.234 | 0.12 | 1.596 ± 0.01 (±10) | … |
| 5 | Photoresist A2-1350J | 2.30 | 0.226 | 0.18 | 1.64 ±0.01 (±10) | … |
| 6 | Photoresist AZ-1350B | 0.50 | 0.226 | 0.21 | 1.64 ±0.01 (±10) | … |
| 7 | SiO2 (electron beam deposition) | … | … | … | 1.471 ± 0.001 (±1) | 1.468 |
| 8 | SnO2 (CVD) | 0.27 | 0.162 | 0.66 | 2.15 ± 0.01 (±8) | … |
| 9 | SixNy (plasma deposition from N2/SiH4) | 0.21 | 0.143 | 0.46 | 2.41 ± 0.03 (±15) | … |
All films were coated on a 1.5-mm thick glass plate (refractive index ~1.5 at 6328 Å) and the above referred results were obtained with the setup illustrated in
Fig. 3. The reported results are averages of 4–10 individual measurements on the same sample. The measured index of refraction
n = tan
θB is reported with its uncertainty and, in parentheses, the corresponding angular uncertainty is shown in minutes. The last column reports some refractive indices available from references and, unless stated otherwise, they refer to λ = 5893 Å. The meaning of
dc is reported in Ref.
5. Samples with thickness
h approaching integer times
dc [that is, frac(
h/
dc) ≃ 0] are not able to be measured (see sample No. 2) and those approaching frac(
h/
dc) ≃ 0.5 are in optimal conditions for measurement. Thickness
h was measured on the groove borders using an interferential microscope.
9 Most of the samples, however, were not aluminized as should be required for an accurate interferential measurement. Nevertheless even for the ninth sample, where the hindering multiple reflections at the film–substrate interface are more relevant, this effect appeared small enough not to be worth considering.
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