[labnetwork] plasma etching of niobium

[Manish Keswani]

Thank you Kamal for your response. I wanted to talk to a few folks on this
topic and get their input before replying to your email so I couldn't get
back to you sooner.

I think with plasma etch, it may not be that straightforward to create this
pattern. If we select a higher ratio of C4F8 to CF4, it will passivate more
on the top and less on the bottom, which will provide a tapered profile
(trapezoidal, smaller opening at the top), but it may be challenging to
achieve a slope of 45 deg.

Another option is to create a resits profile with a 45 deg slope
(trapezoid) using grayscale lithography and then fill the openings (inverse
trapezoid, larger top) with the metal (Nb) using sputter or ebeam,
planarize, and remove the resist.

Let me know if this doesn't make sense.

Thanks,
Manish


On Fri, Oct 8, 2021 at 8:07 PM Kamal Yadav <kamal.yadav at gmail.com> wrote:

> Hi Manish,
>
> Will positive resist give you 45 degree walls for some dose & focus
> condition in your exposure tool, probably that's possible, I think if you
> explore the range. And then if you dry etch, the profile should transfer to
> Nb in CF4 chemistry or the chemistry you want to use. Your mask needs to be
> made (shifted) accordingly such that your features are trapezoidal, smaller
> dimension on top.
>
> Not sure if you have considered this.
>
> On Fri, Oct 8, 2021 at 5:11 PM Manish Keswani <manish.keswani01 at gmail.com>
> wrote:
>
>> Happy Friday Everyone,
>>
>> I have a question about the plasma etching of Niobium. One of our
>> customers is interested in creating sloped sidewall (45 deg, trapezoidal)
>> patterns in Nb (500 nm thick film). Although we have some experience
>> creating similar patterns in silicon and have a general idea about which
>> direction to go in terms of process parameters, we have not done this for
>> Nb. The features are 600 microns x 600 microns or 3 microns x 600 microns
>> openings after the Litho step.
>>
>> Does anyone have suggestions?
>>
>> Thanks,
>> Manish Keswani
>> Lawrence Livermore National Laboratory
>>
>>
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>
>
> --
> Thanks,
> Kamal
>
>
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