The disclosed subject matter relates generally to the field of semiconductor device manufacturing, and more particularly, to a method for reducing wettability of ruthenium liner at corner interface and a device made according to the method.
A conventional integrated circuit device, such as a microprocessor, is typically comprised of many thousands of semiconductor devices, e.g., transistors, formed above the surface of a semi-conductive substrate. For the integrated circuit device to function, the transistors must be electrically connected to one another through conductive interconnect structures. The back end of line (BEOL) is the second portion of integrated circuit fabrication where the individual devices (transistors, capacitors, resistors, etc.) get interconnected with wiring on device. BEOL generally begins when the first layer of metal is deposited on the wafer. It includes contacts, insulating layers (dielectrics), metal levels, and bonding sites for chip-to-package connections. Many modern integrated circuit devices are very densely packed, i.e., there is very little space between the transistors formed above the substrate. Thus, these conductive interconnect structures must be made in multiple layers to conserve plot space on the semiconductor substrate.
The conductive interconnect structures are typically accomplished through the formation of a plurality of conductive lines and conductive plugs, commonly referred to as contacts or vias, formed in alternative layers of dielectric materials formed on the device. As is readily apparent to those skilled in the art, the conductive plugs are means by which various layers of conductive lines, and/or semiconductor devices, may be electrically coupled to one another. The conductive lines that connect the various interconnect structures are commonly formed in trenches defined in the dielectric layers.
A contact is generally used to define an interconnect structure (e.g., using polysilicon or metal) to an underlying polysilicon layer (e.g., source/drain or gate region of a transistor), while a via denotes a metal to metal interconnect structure. In either case, a contact opening is formed in an insulating layer overlaying the conductive member. A second conductive layer is then formed over the contact opening and electrical communication is established with the conductive member.
One technique for reducing the size of the features formed on the semiconductor device involves the use of copper for the lines and interconnections in conjunction with new dielectric materials having lower dielectric constants than previously achievable with common dielectric material choices. Standard dielectric materials such as silicon dioxide, TEOS, and F-TEOS have dielectric constants greater than 3. The new dielectric materials, commonly referred to as low-k dielectrics, have dielectric constants less than 3, and thus, allow greater device densities, due to their more efficient isolation capabilities. One suck low-k dielectric is sold under the name of Black Diamond, by Applied Materials, Inc.
Typical interconnect features include a barrier layer for inhibiting electromigration and a seed layer to provide a starting template for the bulk copper fill needed to complete the interconnect. Due to continuous scaling to smaller dimensions, the fabrication process for BEOL metal features must be tightly controlled to address geometries on a scale of sub-nanometers. Ruthenium (Ru) has been proposed as a seed enhancement layer to improve the copper seed coverage, thereby enhancing the copper fill. A ruthenium layer allows direct copper plating, but copper wettability on ruthenium is so good that there is no copper recess at the interface of copper and ruthenium at the upper outer corners of the metal features. These regions, referred to as “triple points” can have a negative impact on reliability. The copper may be at the same height as the ruthenium liner, or the copper can even creep over the top of the ruthenium and migrate along the interlayer-dielectric interface thus inducing early failures.
This section of this document is intended to introduce various aspects of art that may be related to various aspects of the disclosed subject matter described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the disclosed subject matter. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. The disclosed subject matter is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.