For the LIGA process, thick PMMA layers (up to 500 microns) is the
choice resist material.  After the exposure and development, metal is
electrodeposited in the PMMA mold. It is then necessary to strip off all the
remaining PMMA.  One method for removing the leftover PMMA is to 'flood expose'
all the PMMA with x-ray and use a developing solution to cleanly remove the
exposed resist.  However, x-ray exposure is done using expensive and not-so-
easily available synchrotron radiation source.  A more economical method would
be to use a solvent.  I have used acetone as a solvent followed by an IPA and DI
water rinse.  But this method doesn't work very well; the PMMA is not cleanly
removed.  There is always some PMMA left over to cause problems during SEM
observations.

Does anyone know a better solvent or method of removing thick PMMA resist
layers?

Thanks in advance.
Yohannes M. Desta
LSU mSET