| This study explores the concept of alloying copper with either 2 at. % magnesium or 0.5 at. % aluminum to solve the problems associated with the use of copper in metallization schemes without significantly increasing the resistivity of copper. These elements are expected to move to all the interfaces of the copper and oxidize in the presence of oxygen. The oxide thus formed is expected to improve adhesion, provide oxidation resistance, and stop the diffusion of copper into the underlying silicon oxide.; The results indicate that, with a proper thermal treatment, the resistivity of copper-2 at. % magnesium and copper-0.5 at. % aluminum were close to pure copper value although copper alloyed with aluminum showed higher resistivity than copper alloyed with magnesium. After a thermal anneal, a thin oxide barrier, rich in the alloying element formed at the metal-environment interface for both copper alloys. The high resolution TEM micrographs indicate that a barrier formed at the copper-magnesium-SiO2 interface.; The copper alloys, when compared to pure copper, had different microstructures and textures. This difference in texture could have broad implications in the physical properties of the film.; Copper-2 at. % magnesium had excellent adhesion and oxidation resistance, after a thermal anneal.; The electrical testing indicates that the thin barrier formed at the interface between copper-2 at. % magnesium and the dielectric stops or severely reduces the movement of copper ions into the dielectric. The MOS capacitors tested showed no shift in flatband voltage that would indicate the presence of copper ions in the dielectric. The barrier formed by copper-0.5 at % aluminum did not prove effective in stopping the movement of copper into the dielectric, but it did manage to slow down the movement of copper ions at high bias temperatures.; The results indicate that copper alloyed with 2 at. % magnesium, after a thermal anneal, will be an excellent metal to be used as an interconnect on SiO2. The thin barrier formed by the magnesium at all surfaces may eliminate the use of adhesion/diffusion barriers. (Abstract shortened by UMI.)... |
