> I have trenches in silicon with vertical sidewalls with a depth of about 70µm
> and a width of about 8µm. I have sputtered 1µm of gold on the substrate and I
> could see that the gold penetrates about 24µm into the trenches. There is
> almost no gold below 24µm. This shows that very narrow trenches can be coated
> with an aspect ratio of up to 3:1. My goal is to coat the vertical sidewalls
of
> the trenches with a 400-1000nm thick layer of gold. This first test shows that
> an aspect ratio of 3:1 can be coated with gold very well.
>
> What would you think if the trench width is increased to 70µm and the depth
> is 250µm? (aspect ratio=3.5:1) Do you think that it will be easier to coat a
> trench which has nearly the same aspect ratio (3.5:1), but which is
> significantly wider (70µm)?

For the 8µm trench, a 1µm film will already decrease the top opening to 6µm
or less, so for 70µm width you can expect slightly better performance.

Using a heavy sputter gas (Kr or Xe) at high pressure will improve sidewall
coverage, at the expense of bottom coverage and inreased resistivity. What
one would really want to do is use high temperature, but then you'd need a
barrier layer under the gold to prevent diffusion into the Si.

best regards,
klaus
--
Klaus Beschorner
Metron Technology Europe, PVD (Eclipse) Process Manager
Drosselweg 6,71120 Grafenau,Germany. Tel +49-7033-45683