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

Abstract

Reactively sputtered amorphous TaSixNy (x = 1.4, v = 2.5) films of different thicknesses (5 to 40 nm) serving as diffusion barriers were studied for Cu metallization. The Cu/TaSixNy/p(+)n junction diodes with 5-nm-thick TaSixNy 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 thermal stability temperatures of the Cu/TaSixNy/p(+)n junction diodes were increased 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 structure accelerates the formation of Ta-silicide. Failure of the amorphous TaSixNy diffusion barrier is presumably due to Cu diffusion through the barrier layer by way of localized defects.