Preparation And Characterization Of Ru-TiN Diffution Barrier

As integrated circuits are scaled down to achieve miniaturization and greater integration, the quality of thin film interconnections is becoming a critical factor that determines their performance and reliability. The RC interconnection delay is one of the most important factors influencing circuit performance, where R is resistance of the interconnection and C is its associated total capacitance. Reducing RC delay to lower than or to equal to device delay has become both a material as well as an interconnection design/architecture challenge. In order to avoid the metallization of Cu with other elements like Si, one barrier layer must be introduced between Cu and Si. The previous work indicates that Ru-based thin film is one very promising barrier layer, which is potential to be the next generation of barrier layer in integrated circuits. As is known, amorphous Ru layer is the ideal candidate barrier layer because it does not have any grain boundary. However, Ru tends to crystallize during deposition. N incorporation into Ru layer could result in amorphorization of Ru, which greatly enhances the diffusion resistance property. Unfortunately, during thermal annealing, N will be degassed out and result in deterioration. In this dissertation, we propose to introduce Ti element, which easily react with N to stabilize the N atoms.The Ru-TiN composite thin films were prepared by DC magnetron sputtering deposition method. The effects of the deposition parameters like N2 flow rate, sputtering power density of Ti target on thickness, phase composition, chemical states and resistivity of thin films were systematically investigated. The effects of thermal annealing on the microstructure, crystallization and resistivity of the thin films were also studied. The effect of Ru-TiN nanocomposite thin films on diffusion of Cu was digested preliminarily.The results showed that with N2 flow rate increasing the deposition rate basically decreases and Ru was amorphorized initially and then crystallized. The resistivity of thin films demonstrates the increasing trend. As the power of Ti target increases, the deposition of thin film shows reverse"V"trend, peaking at 190 W. The preferred orientation of Ru also changed as the power density increased. When the power is further increased, Ti has two chemical states: one forms Ti-N bonds and the other exists in the forms of metal Ti. After thermal annealing treatment, the thin films were further crystallized and grain size becomes larger. However, the N content in the films was dramatically reduced. It is interesting that N could be still existent in the film if the thermal annealing temperature is not so high. Moreover, the resistivity of the films was also reduced after thermal annealing treatment. The preliminary results show that Ru-TiN layer plays positive role in preventing the Cu diffusion at elevated temperatures.