Hi,
Coating uniformity depends on substrate holder type (single or planetary rotation), chamber dimensions, evaporator position, coated surface shape and some other factors. For industrial coating machines with single rotated substrate holder coating uniformity less than 5% is usually specified. For machines with substrate holder double planetary rotation the thickness uniformity about or even less than 1% is available, sometimes the extra rotating mask is used. However it doesn't mean that you can obtain so high uniformity for any coating made of any materials. Uniformity also depends on evaporated material distribution in the chamber volume which may vary for different materials and during a time of evaporation. We usually obtain uniformity in mass production of e-beam evaporated multilayer dielectric coatings (not the thickness but optical properties, it is close but not the same) less than 2% in the chamber Dia.72"x72" with double planetary rotating substrate holder and rotating mask. But not for all coatings, for some of them less than 1%, for some - about 5%.
Best regards,
Vladimir Chutko
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On 4/13/2011 12:06 AM, deepak wrote:
Hi,
This is my first post in the group. I want to know the tolerance in thickness variation (in nm) of Aluminium coating, acceptable and expected from professional and amateur coaters.
Mr Jan van Gastel in interferometry group has finished a mirror accurate to<5nm. So I think coating error introduced in 100 nm film thickness would be less than 1 nm. Is such precision achieved routinely by coaters in this group?
Thanks and with regards,
Deepak
Ahmedabad, India
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