Electroless Deposition of Thin Copper-Molybdenum Layers for ULSI Applications
Electroless deposition of thin copper-molybdenum layers is a method of producing highly reliable nano-wires for interconnect applications to solve the problems in the use of copper interconnects. By adding small amount of molybdenum the copper resistance to electromigration is increased. This reduces corrosion and prevents contamination of the silicon substrate. This innovation is of major importance to the manufacturers of ultra large-scale integration (ULSI) applications. Copper is a preferred material and is lower in cost, hence this innovation can significantly impact on both profit margins and performance in the ULSI industry.
The use of electroless deposition of thin copper-molybdenum wires is much more reliable and cost-effective for networks than most current interconnects, which use aluminum. The innovation is designed to serve the ultra large-scale integration (ULSI) technologies and the integrated circuit (IC) manufacturing industry.
Leading edge interconnect manufacturing processes today operate within critical dimensions. The downscaling increases the line serial resistance, lowers its capacitance to ground, and increases the coupling capacitance between lines. Therefore, a decrease in the metal resistance of the interconnect and in the interlevel insulators dielectric constant is highly desirable. Adding small quantities of refractory metals, such as molybdenum, to copper alloys increases the melting point, improves the mechanical properties, enhances the corrosion resistance, and reduces the interaction with the interlevel dielectrics. The electroless deposition technique offers quite a few advantages: low processing temperature, high selectivity, self-aligning and conformal deposition, i.e. the ability for filling high aspect ratio features, and thus enables the creation of the copper-molybdenum wires.