Helllo Roger,

We have used (Ethylene Diamine + Pyrocatechol ) + Pyrazine solution and used
SiO2 as mask for etching thru holes on a Si wafer <100> during my grad school in
IIT Bombay. The pyrazine slows down the etch rate of SiO2 in EDP considerably
such that thermally grown oxide ~0.5 micons ( Wet + Dry) is suuficient to serve
as a mask. So my advice is that pattern SiO2 using photoresist, and then etch
the wafer  in EDP + Pyrazine solution with SiO2 as etch mask.

Regards
Amit Shiwalkar


Adam Wengrow wrote:

> Roger, you may want to try a sacrificial gold layer.  The gold will stand up
> to a through etch in KOH (providing its thick enough to avoid pinholes) and
> it can later be selectively removed with KI without effecting you Ti or Al
> structures.  I don't know any way of getting photoresist alone to stand up
> to KOH for that long.
>
> ADAM
>
> Quoting Roger Brennan :
>
> > Greetings:
> > Is the following feasible?
> > 1) Mask <100> silicon wafers having aluminum and titanium structures.
> > 2) Etch holes all the way through (300 microns) etching from both sides
> >
> > using EDP or KOH.
> > 3) Remove the photoresist without disturbing the Ti or Al.  (I worry
> > about
> > galvanic effects during the stripping due to the presence of Si, Ti, and
> >
> > Al.)
> > It is my understanding that well cured SU8 might work as the resist and
> >
> > SMST-M might work as the stripper.  The following is all I know about
> > the
> > stripper:
> > "SMST-M This formulation is the standard formulation. It doesn't attact
> >
> > metals such as aluminium, gold, titanium, chromium, but a slight attact
> > of
> > copper and nickel can be observed."
> >
> > I have contacted the vendor of the stripper, SOTEC MICROSYSTEMS SA, but
> >
> > often users know more than the vendor.
> >
> >
> >
> > Roger Brennan
> > Home:
> > 1403 Forrestal Avenue
> > San Jose, CA 95110
> > (408)453-0711 (telephone)
> > (408)573-9407 (fax)
> > [email protected]
> >
> > Work:
> > Endevco
> > 355 N. Pastoria Ave.
> > Sunnyvale, CA 94085
> > 408-739-3533 ext 204
> > [email protected]
> > _______________________________________________
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--
Amit Shiwalkar

Research Engineer
Biomorphic VLSI Inc.
4165 E Thousand Oaks Blvd. Suite 180
Westlake Village,
CA 91361
USA


"Your reality is a figment of my Imagination"
      ......... To me you exist because I imagine that you do.