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

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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