Hi Gareth,

I used to work with very thin germanium chips which would sometimes shatter
when spinning or exposing.  I tried a few different things (varnish, wax),
but ended up mounting them on larger silicon chips with two or three narrow
strips of thin double-sided kapton tape.  It was robust enough to go through
all normal processing (190C was the max temperature it saw) and it turns out
that while it is very resistant to acetone and IPA, if you soak it for a
while in TCE, it will slide right off.  It helps if you keep it flat and off
the bottom of the beaker when you do this, otherwise you can end up with
bits of polymer gunk on your devices.  If you use thin enough strips of tape
you may also be able to carefully slide it off without the TCE depending on
how fragile your dies are.

Also, I remember that it can be a bit tricky to spin even layers of SU8 on
very small samples, and be careful to not get the SU8 between the die and
whatever you mount it on.

Good luck,

Alex

On Thu, Aug 26, 2010 at 6:47 AM, Gareth Jenkins wrote:

> Hi
>
> I need to temporarily mount a small die onto a 4 inch wafer so I can spin a
> layer of resist (SU-8).
>
> I don't want to use any tape as being small and fragile, they may be
> difficult to remove.
>
> Someone has mentioned a high melting temperature wax type adhesive for
> doing
> this kind of job. Can anyone recommend a suitable product?
> Would standard paraffin wax work? Ideally I would leave the die mounted on
> the wafer to do the baking/lithography. Would it be a big problem if this
> melts during the baking?
>
> Best regards
>
> Gareth