Dear all,

     I now spin-coated a PDMS layer(about 120um) to cover the electroplated
structures on one side of a Si wafer.And I want to etch the Si right underneath
the electroplated structures from the back side using KOH.
     But when completely etched  the Si(about 500um), most of the electroplated
structures are not enveloped in the PDMS membrane.

     Does anybody here have the experience about this processing ?  Please help
me!

     And should I leave a thin layer of Si (for example 10~20um) un-etched, and
then use RIE or any other means to etch the remain Si? I didn't such process,
could anybody give me some information about them?

  Your advice is invaluable for me!

    Best regards !
                                                  yous sincerely
                                                      Yufeng Su