Integration of silver and copper metallization with low dielectric parylene-N, physical and electrical characterization

The objective of this research was to examine the characteristics of copper (Cu) and silver (Ag) thin films and to determine their capability as advanced interconnect metals with Parylene-n (Pa- n) as a low dielectric constant material. Pa-n and copper or silver are being studied for ultra-large-scale-integration circuits because of their favorable properties. These include low dielectric constant (2.65), negligible water take-up, chemical inertness, low temperature deposition as well as compatibility with current integrated circuits manufacturing for Pa-n and the low resistivity, high electromigration resistance for Cu and Ag when compared with aluminum. Cu and Ag systems with Pa- n were investigated to understand various reliability issues.; Copper diffusion was observed at and above 300°C in Pa-n correlated to an increase in the crystallinity of the α-phase and the subsequent transformation to the more open β-phase. Titanium oxynitride/Titanium (TiNO/Ti) was successfully implemented as a diffusion barrier. Incorporation of an intermediate titanium layer reduced the residual stresses and thermal mismatch between Pa-n and TiN.; Thermal stability and texturing of Ag films on Pa-n were confirmed using X-ray diffraction analysis. Rutherford backscattering spectrometry and secondary ion mass spectroscopy analysis showed insignificant diffusion of Ag in Pa-n.; The adhesion of copper and silver with Pa-n was studied because the durability and reliability of thin films are largely dependent upon their adhesion with each other. Contact angle measurements were used to measure adhesion energies of Cu and Ag layers on substrates of both SiO ₂ and Pa-n. Oxygen plasma surface treatment of Pa- n showed drastic improvement of adhesion between Ag and Pa- n. The increase in adhesion for the Ag/Pa-n system was attributed to increased roughness and presence of carbonyl groups on the surface.; Electromigration studies were also considered for electrical reliability and compatibilities of the materials of choice. The actual temperature of the lines under study is the most important parameter to evaluate the effect of Joule heating for the reliability analysis using electromigration. Activation energy of 0.33 eV suggested a surface diffusion assisted electromigration failure. Nucleation of voids at numerous points simultaneously was observed in secondary electron microscopy.