In this study, the physical and electrical properties as well as thermal stability of sputter-deposited titanium carbide (TiCx) films as diffusion barriers for Cu metallization were investigated for the first time. With thermal annealing in N-2 ambient for 30 min, the unpatterned Cu (2000 Angstrom)/TiCx (500 Angstrom)/n-Si structure was found to be metallurgically stable up to a temperature between 600 and 650 degreesC without formation of a Cu3Si phase, while the reverse leakage current of the patterned Cu (2000 Angstrom )TiCx (500 Angstrom)/p(+) n-Si diode structures showed that the TiCx barrier layer was capable of withstanding annealing temperatures up to 500 degreesC. The failure of the TiCx layer after high temperature annealing is attributed to the diffusion of Cu along localized defects or grain boundaries of the TiCx barrier layer into Si substrate, which caused the high junction leakage currents for the patterned structure and formation of Cu3Si for the unpatterned structure.