Micromachining Using Porous Silicon

Porous silicon was proposed since 1994 for micromachining, but at first only for sacrificial layers [193–198]. Lehmann considered it as new base material for MEMS using the high internal surface of macropores in 1996 [228]. Tjerkstra combined porosification and electropolishing of Si to form free-standing layers of porous Si to separate concentric microchannels [229] and uses isotropic electropolishing to micromachine buried microchannels [230]. All the devices have in common that they are mechanically static.