Reactively sputtered amorphous TaSixNy films serving as barrier layer against copper diffusion

Reactively sputtered amorphous TaSixNy (x = 1.4, v = 2.5) films of differen t thicknesses (5 to 40 nm) serving as diffusion barriers were studied for C u metallization. The Cu/TaSixNy/p(+)n junction diodes with 5-nm-thick TaSix Ny barriers were able to sustain a 30 min thermal annealing at temperatures up to 400 degreesC without degradation of the electrical characteristics. With thicker barriers of 10, 20- and 40-nm-thick TaSixNy layers, the therma l stability temperatures of the Cu/TaSixNy/p(+)n junction diodes were incre ased to 500, 550 and 650 degreesC, respectively. The amorphism, of TaSixNy films on Si substrates remains unchanged at temperatures up to 800 degreesC , whereas the presence of a Cu overlayer on the surface of the TaSixNy/Si s tructure accelerates the formation of Ta-silicide. Failure of the amorphous TaSixNy diffusion barrier is presumably due to Cu diffusion through the ba rrier layer by way of localized defects.