Characteristics of electrodeposited CoWP capping layers using alkali-metal-free precursors

CoWP films, used as a capping layer for a copper interconnection, were electrodeposited using alkali-metal-free precursors, and the effect of the electrolyte concentration on the film characteristics such as the thickness, composition, and microstructure was investigated. The current density and the film thickness increased with the concentration of cobalt, tungsten, and phosphorous precursors. When the cobalt ion concentration in the electrolyte was increased from 0.01 to 0.09M, the cobalt content in the film increased from 67 to 89 at%, while the tungsten and phosphorous contents decreased from 16 to 0.7 and 17 to 10 at%, respectively. The tungsten and phosphorous contents also increased as their corresponding concentrations increased in the electrolyte. Microstructural analyses showed that the tungsten and phosphorous content in the film greatly affected the crystallinity of the CoWP films electrodeposited using alkali-metal-free precursors.