Chemical etching of a semiconductive wafer by undercutting an etch stopped layer

Claim 1

In a method for making three-dimensional structures by chemical etching of a semiconductive wafer, the steps of: providing a pair of etch stopped layers on opposite major faces of a semiconductive wafer of semiconductive material; introducing an etchant through openings in both of said etch stopped layers; etching the substrate semiconductor through said openings in both etch stopped layers to undercut substantial portions of both of said etch stopped layers; terminating the etch of substrate material so as to leave undercut structure in both of said etch stopped layers interconnected by interconnecting substrate semiconductive material whereby a three-dimensional structure is made; and patterning the openings of said etch stopped layers to define a frame structure and cantilever beam portions of said etch stopped layers on both sides of said wafer, said cantilever beam portions being undercut by said etchant when the etch is terminated, one end of the undercut cantilever beam portions being supported from the frame structure and the other ends being supported from said interconnecting substrate material which is free to move relative to said frame structure by bending of the undercut cantilever beam portions.