Patterning of tantalum polycide films

Gate level interconnect composed of a layer of doped polysilicon covered by a refractory metal silicide (polycide structure) is becoming an important feature of some integrated circuit technologies. These composite structures retain the relatively well characterized polysilicon/SiO/sup 2/ interface while permitting a lower resistivity than possible with polysilicon alone. Dry etching chemistries used for patterning polysilicon are not generally compatible with these composite materials, often producing an undesirable etched line profile or other complications. For example, a fluorine based plasma will typically etch the polysilicon out from under the silicide resulting in an overhang that will reduce step coverage by subsequent depositions. It has been recently shown that by adding C1/sup 2/ to an SF/sup 6/ plasma, a continuous profile can be formed on Ta polycide lines. In this paper the authors discuss the etching behavior of TaSi/sup 2//polysilicon films in a BC1/sup 3//C1/sup 2/ based reactive ion etching process. Control of the etched line profile by variation of the process parameters is emphasized.