Transient fuse structures: The role of metal etching vs. dielectric deposition

Transient fuse (or T-fuse) structures have been used in recent years to study charging from metal etching. However, we identify here a case where the charging detected by the T-fuse came not from metal overetching but from the subsequent dielectric deposition step. This HDP CVD oxide deposition process caused charging through metal finger antennas that appears much like metal overetch-induced charging, but experiments varying etch process parameters or omitting the deposition step showed that deposition was the source of charging. Presumably the charging occurred early in the deposition process, when the metal antennas were exposed to the deposition plasma. The space width dependence of charging had a signature unlike that expected from electron shading during metal etching: charging diminished rather than increased as space width narrowed