Method for producing a buried interconnect rail of an integrated circuit chip

Abstract

A method includes forming a trench in a semiconductor layer of a device wafer and depositing a liner on the trench sidewalls. The liner is removed from the trench bottom, and the trench is deepened anisotropically to form an extension fully along the trench, or locally by applying a mask. The semiconductor material is removed outwardly from the extension by etching to create a cavity wider than the trench and below the liner. A space formed by the trench and cavity is filled with electrically conductive material to form a buried interconnect rail comprising a narrow portion in the trench and a wider portion in the cavity. The wider portion can be contacted by a TSV connection, enabling a contact area between the connection and buried rail. The etching forms a wider rail portion at a location remote from active devices formed on the front surface of the semiconductor layer.