Vikrant,

I'm my experience the higher the topography, the thicker the resist you
need to cover it. But, the actual resist thickness (as determined on a
flat wafer) is dependent on the specifics of the topography and the
subsequent process in which the resist is used. So, for example, I can
coat bond pads which are 2um high with 1um resist and run a wet etch
afterward. To cover a 5um step with subsequent DRIE etch I need a 7um
resist.

There are two alternative you may look into. There are spray on resists
(some even come in a can, or you can use an air brush). I have never had
good luck with this method. but it may work great for what you are doing.

Second, I have heard of, but never used electrochemically deposited
resists. I think Dupont makes them...

Rob MacDonald
>
> hello,
>
> We have been trying to pattern SiN deposited on textured Si using
> lithography, but we are unable to obtain desire pattern, as the entire SiN
> gets etched in BHF, the height of the textured surfaces are about 8-10 um.
> Do we need to spin coat a thick layer so that the textured surface is
> covered, or there is there something else?
>
> Do let us know.
>
> vikrant