Precursor Molecules for Thin-Film Diffusion Barriers that Prevent Electrical Shorts in Integrated Circuits

Improves Diffusion Barriers in Small Integrated Circuits

These tungsten nitrido precursor molecules are starting materials for low-temperature deposition of tungsten carbonitride (WNCx) thin films that serve as diffusion barriers that prevent electrical shorts in integrated circuits. A common example is prevention of Cu diffusion into other areas within an integrated circuit that uses Cu in its metallization scheme. Virtually all modern consumer electronics, including mobile phones, personal music players, computers and televisions, contain at least one integrated circuit. Since Cu at trace amounts will harm transistors and other Si-based devices, integrated circuits could not function properly without diffusion barriers. The interest in faster and more energy efficient electronic devices has resulted in the need for ever-thinning diffusion barriers to defend against Cu transport into the Si area of the device. University of Florida researchers have developed tungsten nitrido precursor molecules that, when employed by chemical vapor deposition (CVD) to deposit diffusion barriers for integrated circuit technologies, have several benefits over current processes. The resulting barrier films boast many desirable features, such as uniform thickness with controlled electrical conductivity and strong bonding characteristics.

Application

These tungsten nitrido precursor molecules can be used to make improved diffusion barriers for integrated circuits, significantly reducing device failure due to Cu contamination by transport from Cu conductors in integrated circuits.

Advantages

• Has a very low deposition temperature, as low as 75 °C, which opens barrier, conductor, catalyst, and high-hardness applications for a broader range of materials
• Relatively easy to transport the precursor under its own vapor pressure or as an aerosol in a suitable solvent.
• Bond re-ordering allows creation of highly disordered films (i.e. amorphous), which are superior chemical barriers compared to polycrystalline films.
• Potential for high conformality deposition, allowing for use in integrated circuits with increasingly smaller feature sizes
• Single-step electrochemical deposition (ECD) and acceptable chemical mechanical polishing (CMP) etching rates permit higher throughput of devices.

Technology

University of Florida researchers have developed tungsten nitrido precursor molecules that can be used to create diffusion barriers for integrated circuits, for example as a Cu barrier in advanced metallization schemes. Because tungsten nitride is relatively thermally stable and deposits in a highly conformal way, it works well as a diffusion barrier for small integrated circuits. A single N atom is bonded to metal tungsten and low-temperature partial thermal decomposition yields a solid that contains an extended network of W-N bonds. Altering the order of these bonds changes the material’s properties. Electrical conductivity and strength can be varied by alloying with carbon.