Effect of Zr and Cr Doping on the Structure and Properties of Copper Interconnection Thin Films

The effects of zirconium (Zr) and chromium (Cr) elements doping on the structure and properties of copper (Cu) interconnection thin films were investigated. Cu, Cu(Zr), Cu(Cr), and Cu(ZrCr) interconnection films were deposited on SiO2/Si substrates by direct current magnetron sputtering technique, and the films were annealed under vacuum condition at the temperature of 400-800 degrees C for 1 h. The surface morphologies, microstructure, and electrical properties of the films were tested and analyzed by SEM, XRD, and four probes method. The results show that single element doping of Zr or Cr improves the thermal stability of Cu interconnect films. The precipitation of Zr or Cr elements prevents mutual diffusion between Cu film and Si substrate, and suppresses the growth and aggregation of the grains, which make the films maintain good properties. After vacuum annealing at 700 degrees C, the resistivity of the Cu(Zr) or Cu(Cr) film is less than 10 mu S<middle dot>cm (that of pure Cu film is 74.70 mu S<middle dot>cm). The co-doping of Zr and Cr elements further improves the thermal stability of Cu interconnection films while maintaining low resistivity and interconnect reliability. Especially after vacuum annealing at 800 degrees C, the resistivity of Cu(ZrCr) film is as low as 3.23 mu S<middle dot>cm (that of pure Cu film is 103.50 mu S<middle dot>cm).