With PMMA, it helps a lot to hard-bake between each application or you
end up with pretty much exactly your problem (because the previous
layers are soluble in the fresh resist).  Not tried Fox, nor do I know
if it even needs baking, so this could be a stupid answer!

Cheers,

Andy

James Paul Grant wrote:
> Hello,
>
> I would like to spin multiple layers of Fox 16 (aka HSQ) e-beam resist.
> I have tried a couple of times to do this but I only end up with a
> resist thickness after development of around 1.1 times that of a single
> coating step.
>
> Does anyone have any ideas?
>
> Thanks,
>
> Dr. James Paul Grant