A TAILORED BARRIER LAYER WHICH PROVIDES IMPROVED COPPER INTERCONNECT ELECTROMIGRATION RESISTANCE

摘要

Disclosed herein is a barrier layer structure useful in forming copper interconnects and electrical contacts of semiconductor devices. The barrier layer structure comprises a first layer of TaNx which is applied directly over the substrate, followed by a second layer of Ta. The TaNx/Ta barrier layer structure provides both a barrier to the diffusion of a copper layer deposited thereover, and enables the formation of a copper layer having a high {111} crystallographic content so that the electromigration resistance of the copper is increased. The TaNx layer, where x ranges from about 0.1 to about 1.5, is sufficiently amorphous to prevent the diffusion of copper into the underlying substrate, which is typically silicon or a dielectric such as silicon dioxide. The thickness of the TaNx and Ta layers used for an interconnect depend on the feature size and aspect ratio; typically, the TaNx layer thickness ranges from about 50 ANGSTROM to about 1,000 ANGSTROM , while the Ta layer thickness ranges from about 20 ANGSTROM to about 500 ANGSTROM . For a contact via, the permissible layer thickness on the via walls must be even more carefully controlled based on feature size and aspect ratio; typically, the TaNx layer thickness ranges from about 10 ANGSTROM to about 300 ANGSTROM , while the Ta layer thickness ranges from about 5 ANGSTROM to about 300 ANGSTROM . The copper layer is deposited at the thickness desired to suit the needs of the device. The copper layer may be deposited using any of the preferred techniques known in the art. Preferably, the entire copper layer, or at least a "seed" layer of copper, is deposited using physical vapor deposition techniques such as sputtering or evaporation, as opposed to CVD or electroplating. Since the crystal orientation of the copper is sensitive to deposition temperature, and since the copper may tend to dewet/delaminate from the barrier layer if the temperature is too high, it is important that the copper be deposited and/or annealed at a temperature of less than about 500 DEG C, and preferably at a temperature of less than about 300 DEG C.