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)?

Any help will be greatly appreciated!

Stephan