Effect of plasma immersion ion implantation on the thermal stability of diffusion barrier layers

Plasma immersion ion implantation technique has been used to synthesize titanium nitride and tantalum nitride layer to acts as diffusion barrier against copper diffusion. Two different doses of nitrogen, 1015 ions/cm2 (low dose) and 1017 ions/cm2 (high dose), were implanted in refractory metal-coated silicon wafers. Diffusion barrier properties of these nitride layers were evaluated after annealing the samples up to 700 °C for 30 min. Sheet resistance, SEM and X-ray diffraction were carried out to investigate the effect of annealing. The highly implanted layer reduces the diffusion of Cu metal through it. The enhancement in its diffusion barrier properties is supposed to be due to nitridation of metal films, which increases the activation energy involved for its chemical reaction with copper metal film.