Thermal performance of sputtered Cu films containing insoluble Zr and Cr for advanced barrierless Cu metallization

Pure Cu films and Cu alloy films containing insoluble substances (Zr and Cr) were deposited on Si(100) substrates, in the presence of interfacial native suboxide (SiOx), by magnetron sputtering. Samples were vacuum annealed between 300°C and 500°C to investigate effects of Zr and Cr additions on the thermal performance of Cu films. After annealing, copper silicides were found in the Cu(Zr) films, while no detectable silicides were observed in Cu and Cu(Cr) films. Upon annealing, Zr accelerated the diffusion and reaction between the film and the substrate, and lowered the thermal stability of Cu(Zr) alloy films on Si substrates, which was ascribed to the ‘purifying effect’ of Zr on the Si substrates. Whereas, Cr prohibited the agglomeration of Cu films at 500°C and decreased the surface roughness. As a result, the diffusion of Cu in Si substrates for Cu(Cr) films was effectively inhibited. In contrast to the high resistivity of Cu(Zr) films, the final resistivity of about 2.76 μΩ·cm was achieved for the Cu(Cr) film. These results indicate that Cu(Cr) films have higher thermal stability than Cu(Zr) films on Si substrates and are preferable in the advanced barrierless Cu metallization.