| Duo to the dimensions diminishing of device and interconnect, the preparation of thin diffusion barrier with good barrier property and lower resistivity become much more challenging with the development of integrated circuits. New materials and techniques are pressingly needed in order to solve this problem. Therefore, people attach importance to the Cu metallization as the seed layer and a barrierless interconnect based on enhanced thermal stability Cu alloy films has been proposed. In this study, Cu(C) films and Cu(Ti) films were deposited onto barrierless Si (100) substrates by magnetron sputtering. The microstructure and properties of added small atom element carbon and large atom element titanium into Cu film were investigated.The results show that about 4 at.% carbon were found present in the as-deposited Cu(C) film. The addition of small atom carbon has the smaller electron scattering effect and would influence the electrical conductivity to a less extent. The Cu(C) film has a low resistivity close to 2.7μΩ.cm at 400℃and maintained a low resistivity of 3.8μΩ·cm even after 9 hour annealing at 400℃. The presence of carbon played an important role in improving the thermal stability of the film. On the one hand, a nanometer-thick passive amorphous layer containing carbon was revealed by transmission electron microscopy observations. The film-substrate interface is clearly defined without any evidence of intermixing after annealing at 400℃for 1 hour. Only diffraction peaks from Cu can be found in the annealed sample at 500℃for 1h. The passive amorphous layer obviously blocked the interface reaction between Cu and Si. On the other hand, the existence of carbon in the Cu film was found to distinctly hinder the growth of Cu grains. The grain sizes of the film annealed at 400℃for 9 hours are less than 100nm. Upon annealing at a high temperature of 700℃for 1 hour, the grain sizes in the film remain basically unchanged. The low electrical resistivity in combination with the high thermal stability makes carbon doping a promising technique for future Cu interconnects on barrierless Si.Comparing to Cu, titanium has larger atom radius and negative enthalpies of mixing with Cu (-6KJ/mole). It can easily form compounds with Cu. As the seed layer, titanium adding into Cu film has larger impact on the resistivity of the film. The result of Cu(Ti) film showed that it had larger effects on the resistivity. In the as deposited Cu(Ti) film, the content of titanium was 0.4 at.% and the resistivity was 23μΩ·cm. Although the resistivity decreased after annealing at 200℃and continued decreased into 6.2μΩ·cm annealed at 700℃for 1h. The overall value of resistivity was relatively high. Cu(Ti) film was well adhered to the substrate without the formation of copper silicide after annealing. In addition, no stratification phenomenon was found after annealing and titanium atoms were still present in the film. The addition of 0.4 at.% into Cu film had the effect of inhibiting the diffusion of Cu and Si. When the content of titanium increased to 2.2 at.%, the stratification phenomenon can be found in the as deposited Cu(Ti) film. Titanium precipitated from the film and reacted with Cu leading to the formation of Cu4Ti. At the same time, the diffusion of Cu into Si occurred and the Cu3Si was formed in the as deposited sample. This results indicated that adding 2.2 at.% Ti into Cu film did not inhibit the diffusion of Cu. On the contrary, it facilitated the diffusion of Cu-Si in a certain extent. Therefore, different content of titanium added into Cu can cause different effects. When the elements with the large atomic radius, negative enthalpies of mixing with Cu, and easyly forming compounds were chose, the small amount of adding did not play the good function.
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