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Epitaxial EPI Polished Sapphire Substrates
Epitaxial EPI polished sapphire substrate or wafer surface can be compared to surface finish that would be suitable for monocrystaline silicon epitaxial layer deposition in semiconductor device manufacturing:
EPI finish on sapphire has become to mean that the finish shall be 3 Angstroms Ra or less.
A common EPI polished sapphire substrate requirement is for manufacture of bright blue and green LEDs.
The tightest tolerance ultra-flat Blue and Green LED 2 in. (50.8 mm) polished Optical Grade Monocrystaline sapphire wafers:
| Orientation |
C-plane (0001) ±0.1 deg. |
| Diameter |
50.8 ±0.05 mm (2 ±0.002 in.) |
| Thickness |
330 ±10 microns or 430 ±10 microns |
| Thickness variation – TTV |
less than 10 microns |
| Bow |
less than 15 microns |
| Surface finish |
EPI polish – less than 3 Angstroms |
| Flatness (restrained) |
less than 5 microns |
| Primary flat |
16 ±0.5 mm |
| Primary flat orientation |
A-plane (1120) ±0.5 deg. |