Dear Daniel,

Most of my colleagues are using photoresist, and they don't seem to have film
cracking at all. When I did the Electron Beam Evaporation, the indicated
temperature is around 40 degree celcius.

For question #2, how long do you usually set your ozone stripper? I tried to
quantize the etch-rate of PMMA using ozone stripper, and I found it to be
~14nm/minute (for unpatterned PMMA) and ~2.4nm/minute (for 300um x 300um square
pattern). Do you think it is better if the sample is not subjected to ozone
stripper before entering
 evaporation?

For the baking temperature, usually the sample is heated at 180 degree C for 90s
(on hot plate).

Kind Regards,
Lando

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Hi Lando,

I use similar process (beside Step 3) without problems. So there are only
two possibilities:

1.) Your evaporation is too hot, mostly if the sample is too close to the
crucible (if it is
 thermal or e-beam evaporation).
However, PMMA is much more robust to heat then most common photoresists. So
check with other users of your equipment if they have the same probs.

2.) Your ozone stripper weakens the PMMA too much. In most cases, a short
oxygen plasma should help to remove any resist residues.

What are your PMMA baking temps?

Best Daniel