hi,

For the front side etching, which material do you want to etch, the silicon
oxide or the underside silicon?  The most important thing is which process will
not damage your microheater. If you just want to etch the silicon oxide under
the microheater, you can use HF etc.  If you want to etch the silcon under the
microheater to make a big hole, maybe SCREAM process is the best choice.

Ren Sen