| As the scale of microelectronic devices continues to shrink, the interconnect delay increasingly dominates the performance of integrated circuits. Porous Materials have been proposed to replace SiO2 as the interlayer dielectric in future devices. The interaction between Copper, the interconnect metal, and the low-kappa interlayer dielectric is important for the chemical and electrical stability of the interconnect system. Diffusion barriers are used to inhibit the Cu/low-kappa chemical interactions. The tradeoff between continuity, adhesion, and thickness places strict requirements on the integrity and stability of these diffusion barriers, especially in systems that include porous low-kappa materials, where the ability to form a continuous layer is affected by the presence of pores underneath. There is as yet no clear understanding at the atomic or molecular level of the dominant transport modes, or the possible interfacial reactions that the barrier needs to prevent. This thesis addresses the issue of Cu injection and diffusion in porous hybrid low-kappa dielectrics of a wide range of porosity and of different types of surface chemistry. The experiments indicate that the effect of surface chemistry is stronger than the effect of porosity and that the injection of Cu is triggered by out-gassing of hydroxyl and water-related species from the dielectric. The effective diffusivity of Cu+ in porous silica decreases with porosity and has an energy of activation of 1.79 eV. Experimental measurements show that the total concentration of Cu + decreases with increasing porosity of the dielectric. This behavior is the combined result of both the chemistry and the morphology of the dielectric since, as porosity increases, the reduced cross-sectional area in the solid leads to reduced diffusion through the porous film. The Cu+ concentration at the Cu/dielectric interface is in the order of 10 23 atoms/m3; but decreases with time and porosity. A physically-based mathematical model of Cu drift is developed. |
