Hi.

It depends on what kind of equipments that you have.

If you have thick enough resist for lift off 2um of Ni and compatible
deposition equipment for 2um Ni evaporation then lift off method will
give you better size control and good vertical side wall profile. Only
chemicals you have to deal with is photo resist and its developer and
Acetone.

If above condition could not be achieved in your case then etching
afterward would be more convenient.
Cause conventional photo resist could be used as mask for Ni etching.
So make relatively smaller hole pattern(smaller than actual hole size
20um) on Photo resist pattern and then chemically wet etch Ni using
etchant such as FeCl3.
Wet chemical etching of Ni in this case will be isotropic so you have
to test and confirm lateral etch rate of Ni to control size of holl
diameter.


BTW you said that what you are dealing with is membrane of Ni, does
that mean Ni will not be attached to any other substrate such as Si
500um thickness wafer? I automatically assumed that you will form 2um
thick Ni onto some other substrate cause you describe lift off process.


Myung Rae Cho

>From Seoul.

On Fri Jan 24 17:09:58 2014, 김덕수 wrote:
> Hi.
>
> at first, I want you to understand that I don't know english very well.
>
>
> I want to form center holes on Ni membrane.
> 
> diameter of membrane is 3~400um(thickness 2um) and of center hole is 2~30um.
> 
> I want to form 5 center holes.
>
> So I thought two methods.
>
>
> 1. Using lift-off process, center holes is formed without etching process.
> 2. after deposition Ni thin film,  etching process is progressed for forming
center holes.
>
>
> I want to know which is more efficient.
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