kapton is not attacked by HF. So u can use kapton as mask and etch HF.
Kapton is also not attacked by KOH.

both etchants you can use separately as two different methods. There may be
little lateral seepage, but when we are talking about 1 mm hole, you may get
1.1 mm, it should not matter much. Glue used in Kapton tape, is not easily
etched by KOH.

On Tue, Dec 7, 2010 at 10:03 PM, Andrew Sarangan wrote:

> I am surprised that this method works. Can you clarify? KOH attacks
> pretty much every resist I've used. What is the function of the HF in
> KOH? How do you prevent lateral seepage with Kapton mask? If it works,
> then it would be a very simple method, but I am skeptical.
>
>
>
> On Tue, Dec 7, 2010 at 1:10 AM, Nabhiraj Yalagoud
>  wrote:
> > hi,
> >
> > Another good way is to etch by HF.
> > coat with PMMA / polymer/ scratch 1 mm diameter by scrubber and remove
> PMMA
> > and etch it in HF / KOH
> >
> > Or put a kapton tape on the wafer by punching a 1 mm hole on the tape.
> and
> > etch it. It may take more time but it is also a very cheap method.
> > remember to tape backside also and shake it while etching.
> >
> > Nabhiraj