Use of multiple etching steps to reduce lateral etch undercut

Abstract

In integrated circuit fabrication, an etch is used that has a lateral component. For example, the etch may be isotropic. Before the isotropic etch of a layer (160), another etch of the same layer is performed. This other etch can be anisotropic. This etch attacks a portion (160X2) of the layer adjacent to the feature to be formed by the isotropic etch. That portion is entirely or partially removed by the anisotropic etch. Then the isotropic etch mask (420) is formed to extend beyond the feature over the location of the portion subjected to the anisotropic etch. If that portion was removed entirely, then the isotropic etch mask may completely seal off the feature to be formed on the side of that portion, so the lateral etching will not occur. If that portion was removed only partially, then the lateral undercut will be impeded because the passage to the feature under the isotropic etch mask will be narrowed.

Dependencies are inferred from the claim text.