Wet and dry etching techniques for the release of sub-micrometre perforated membranes

For the production of microsieves we studied the release of perforated sili con nitride membranes from a silicon substrate. During the release by KOH e tching the pressure build-up due to hydrogen gas formation can be quite lar ge and cause rupture of the membrane. We explored the use of anisotropic et ching with an SF6/O-2 plasma to replace KOH etching. For sub-micrometre por es excellent results were obtained.