The most common method to precisely measure the thickness of anti-reflection coatings is using ellipsometry which looks at the way polarised light is reflected.
A simple method to measure anti-reflection coating is by simply looking at the film colour.
Four multicrystallline wafers covered with films of silicon nitride. The difference in colour is solely due to the thickness of the film.
| Film Thickness (µm) | Colour and Comments |
|---|---|
| 0.05 | Tan |
| 0.07 | Brown |
| 0.10 | Dark violet to red violet |
| 0.12 | Royal Blue |
| 0.15 | Light blue to metallic blue |
| 0.17 | Metallic to very light yellow green |
| 0.20 | Light gold to yellow; slightly metallic |
| 0.22 | Gold with slight yellow orange |
| 0.25 | Orange to melon |
| 0.27 | Red violet |
| 0.30 | Blue to violet blue |
| 0.31 | Blue |
| 0.32 | Blue to blue green |
| 0.34 | Light green |
| 0.35 | Green to yellow green |
| 0.36 | Yellow green |
| 0.37 | Green yellow |
| 0.39 | Yellow |
| 0.41 | Light orange |
| 0.42 | Carnation pink |
| 0.44 | Violet red |
| 0.46 | Red violet |
| 0.47 | Violet |
| 0.48 | Blue violet |
| 0.49 | Blue |
| 0.50 | Blue green |
| 0.52 | Green (broad) |
| 0.54 | Yellow green |
| 0.56 | Green yellow |
| 0.57 | "Yellowish" (actually at times appears to be light creamy gray or metallic) |
| 0.58 | Light orange or yellow to pink borderline |
| 0.60 | Carnation pink |
| 0.63 | Violet red |
| 0.68 | "Bluish" (actually appears more like a mixture between violet red and blue green and looks grayish) |
| 0.72 | Blue green to green (quite broad) |
| 0.77 | "Yellowish" |
| 0.80 | Orange (rather broad for orange) |
| 0.82 | Salmon |
| 0.85 | Dull, light red violet |
| 0.86 | Violet |
| 0.87 | Blue violet |
| 0.89 | Blue |
| 0.92 | Blue green |
| 0.95 | Dull yellow green |
| 0.97 | Yellow to "yellowish" |
| 0.99 | Orange |
| 1.00 | Carnation pink |
| 1.02 | Violet red |
| 1.05 | Red violet |
| 1.06 | Violet |
| 1.07 | Blue violet |
| 1.10 | Green |
| 1.11 | Yellow green |
| 1.12 | Green |
| 1.18 | Violet |
| 1.19 | Red Violet |
| 1.21 | Violet red |
| 1.24 | Carnation pink to salmon |
| 1.25 | Orange |
| 1.28 | "Yellowish" |
| 1.32 | Sky blue to green blue |
| 1.40 | Orange |
| 1.45 | Violet |
| 1.46 | Blue violet |
| 1.50 | Blue |
| 1.54 | Dull yellow green |