Dear community members,

I am using Ni mask made by high resolution e-beam and lift-off process for
DRIE of Si. The structures I am etching are kind of small, down to 60 nm. So
far I was able to reach aspect ratios of around 10 and mask selectivity of
about 50. My problem though is the etching of the Ni mask. The etching
itself is not such a problem, but more the way the mask is being etched
away. It is that the mask is being etched away from its edges towards
inside, which of course negatively effects the etched structure. Is there a
way to improve this? What are the ways to further increase the selectivity?

My process is using CHF3, Ar and O2 chemistry, ICP & RF source, that whole
under low pressure and low power (DC around 300).

Thanks a lot

regards

J.Kouba