Anisotropic etching of metal films in the fabrication of interconnects

A method for anisotropically etching metal interconnects in the fabrication of semiconductor devices, especially ULSI interconnects having high aspect ratios comprises depositing a metal film 3 on an oxide layer 14 of a semiconductor substrate 1 by techniques well-known in the art. A mask layer 4 is then deposited over the metal film with openings defined in the mask layer for patterning of the metal film. Ions are then introduced into an exposed region of the metal film to anisotropically form a converted layer 8 of the metal film comprising a compound of the metal. The introduction of the ions into the metal film can be performed by conventional methods, such as through the use of a reactive ion etch system or an ion implantation system, or by any other method which anisotropically forms the metal compound. The mask layer is then removed by conventional means to leave behind the metal film 3 having the converted layer 8 of the metal compound. Finally, the metal compound is selectively removed by a suitable removal means chosen for its properties in removing the metal compound without causing significant etching or degradation of the metal film itself.