Interconnect structures with different metal materials

Abstract

Techniques are provided herein for forming interconnect structures, such as conductive vias or contacts, that are protected from subsequent processing that includes reactive gas or plasma. A conductive via or contact within an interconnect layer may be formed with a capping layer having a different material to protect the underlying metal material from reacting with certain reactive gas or plasma elements. In some examples, a ruthenium capping layer is formed over a copper via to protect the copper. Other capping layer materials may include tungsten, cobalt, or molybdenum. In some embodiments, the entire conductive via may be formed using one of ruthenium, tungsten, cobalt, or molybdenum, to avoid the use of more reactive metals, such as copper. The capping layer (or less reactive metals) are used to protect the via during a barrier layer doping process that uses a gas or plasma including a chalcogen element (e.g., sulfur and/or selenium).