You might look at

http://www.ammt.de/html/wet_etching.html

They manufacture a holder from PEEK and can do backside window or
illumination.  I'm sure there are others.


>Hi,
>Does any one know where I can get backside protection sample holder for
>KOH wet etching.


Information provided for example only; not an endorsement by NIST.
--

  - Jim Beall 303-497-5989
    beall@boulder.nist.gov