Effects Of Alloying On Microstructure And Electrical Properties Of Cu/SiO₂ System Films

In the end of last century, copper has replaced Aluminum to be interconnection material. It is called Copper Interconnect Technology. However, Cu interconnect still face some difficulties in usage. For example, both antioxidant capacity and corrosion resistance are poor at room temperature. The inter-diffusion of Cu and Si is strong and they easily react. Diffusion barrier, traditionally prepared by vapor deposition, also has its disadvantages such as long producing procedure, higher cost. In addiction, as the size of the interconnection line decline, diffusion barrier indeed occupy the available space of copper.By magnetron sputtering method, thin films of pure Cu and Cu(1.58at% Zr) were deposited on Si(100) and SiO₂ substrate. Samples were vacuum-annealed to investigated the microstructure and properties of Cu and Cu(Zr) films. The mechanism of"Self-formed Diffusion Barriers"and the specific material effects were studied.As shown in X-ray diffraction results, as-deposited Cu films or Cu(Zr) films exhibit Cu(111) and Cu(200) peaks. Both in Si(100) and SiO₂ substrate, Zr doping significantly enhances the (111) texture of Cu films. For Cu(Zr)/Si(100) film system, a small amount of Zr segregate in the interface between film and substrate. The purification effect of Zr induces the formation of Cu3Si, thereby reducing the thermal stability of thin film system. As the increase of annealing temperature, the resistivity of film declines first and then rapidly increases.For Cu(Zr)/SiO₂ system, films still perform great thermal stability after annealed at 500oC. Cross-section morphology, as well as the interfacial analysis results, fully confirmed the conclusion above. Compared with Cu/SiO₂ films, Cu(Zr)/SiO₂ films has much better thermal stability. And their resistivities are similar. Transmission electron microscopy(TEM)result indicates that Zr doping impels the formation of twins, thus enhancing the compositive mechanical properties and electromigration resistance of thin films.As seed layer, Cu(Zr) thin films can optimize the plating copper layer's structure. The films show a stronger (111) texture, and the stress of the films decline.