Investigation of Cu metallization for Si solar cells

For application of copper metallization to silicon solar cells, electrical resistivity of the electroplated Cu was investigated for different annealing conditions: the rapid thermal annealing (RTA) and the vacuum annealing at various temperatures. The characteristics of Ti as the diffusion barrier were also observed. The specific contact resistance between Si and Ti/Cu was measured using Kelvin test pattern. For 8-min electroplated sample, the lowest resistivity of 2.1 μΩ cm was obtained at 300°C RTA condition. For Cu with Ti barrier, 400°C 2 min vacuum-annealed sample showed etch pits whereas 400°C RTA showed no etch pits. A vacuum annealing at 450°C for 30 min reduced the specific contact resistance to 7.2×10−6 Ω cm2.