METAL SEMICONDUCTOR ALLOY STRUCTURE FOR LOW CONTACT RESISTANCE

摘要

Contact via holes are etched in a dielectric material layer overlying a semiconductor layer to expose the topmost surface of the semiconductor layer. The contact via holes are extended into the semiconductor material layer by continuing to etch the semiconductor layer so that a trench having semiconductor sidewalls is formed in the semiconductor material layer. A metal layer is deposited over the dielectric material layer and the sidewalls and bottom surface of the trench. Upon an anneal at an elevated temperature, a metal semiconductor alloy region is formed, which includes a top metal semiconductor alloy portion that includes a cavity therein and a bottom metal semiconductor alloy portion that underlies the cavity and including a horizontal portion. A metal contact via is formed within the cavity so that the top metal semiconductor alloy portion laterally surrounds a bottom portion of a bottom portion of the metal contact via.