I have a problem during make a free standing thin copper film on the
silicon wafer:
I deposit a thin layer copper film(2um) on the silicon wafer, then open a
window on the other side of the wafer. Then I put it into 80 degree KOH
solution to etch from side which has a window. This process takes 4 to 5
hours to etch away the silicon within the window and get a free standing Cu
film. But the difficulty is how to protect the Cu film from a hot KOH? I
know some one uses BCB as the protection layer, but the price is extremely
expensive. If somebody know some other commercial way to protect the thin
Cu film and each to remove? Thanks!