Sacrificial layer

A temporary material supporting another structure during fabrication, then removed selectively. In an oxide-supported polysilicon beam, selective oxide removal makes an air gap while protected substrate contacts retain anchors. Removal must reach beneath the structure without destroying it; a purely vertical etch may not release a lateral overhang.

Selective removal of a sacrificial layer using gaseous reactants rather than a bulk liquid bath. A compatible vapor-phase oxide etch can avoid the liquid drying step responsible for one form of stiction. Selectivity, byproducts, humidity and access to the undercut region still matter.