Influence of Chemical Composition of Pyrophosphate Copper Baths on Properties of Electrodeposited Cu Films

Effects of chemical composition (Cu2+, K4P2O7 and additive concentrations) of baths on properties of Cu thin films electrodeposited from pyrophosphate copper bath were investigated. Current efficiency was increased to be near 100% with increasing Cu2+ concentrations from 0.02 to 0.3 M. Decrease of current efficiency was observed in the range of 1.5 similar to 1.8M K4P2O7 concentration, but current efficiency of about 100% was measured in the ranges of both 0.9 similar to 1.3M and 2.1 similar to 2.4M. The change of additive concentration did not influenced current efficiency. Residual stress of electrodeposited Cu thin films was measured to be about 20 MPa below 0.15 M Cu2+ concentration and increased with the increase of it to 0.25 M. Maximum residual stress of 120 MPa was observed at 0.25M Cu2+ concentration. On the other hand, residual stress decreased from 80 to near 0MPa as K4P2O7 concentration varied from 0.9 to 2.4 M and but The change of additive concentration did not affected on residual stress. Cu2+ and K4P2O7 concentrations significantly affect on surface morphology of electrodeposited Cu thin films, but additive concentration slightly affected. From XRD analysis, the microstructures of electrodeposited Cu thin film was affected from the changes of Cu2+ and K4P2O7 concentrations, but not from that of additive concentration. Strong preferred orientation of (111) peak was observed with increasing Cu2+ and K4P2O7 concentrations.