Electromigration-resistance enhancement with CoWP or CuMn for advanced Cu interconnects

Reliability of silicon integrated circuits

“…To compensate, analogs of the techniques used to improve Al The data indicate that current density exponent can vary between 1 and 2 depending on the relative importance of void nucleation and growth to the failure time. electromigration performance have been introduced for Cu: namely, Cu alloys to limit fast grain boundary diffusion [79][80][81][82][83][84], which controls the rate of electromigration in highly scaled Cu, and the incorporation of metallic cap layers at the Cu surface to impede diffusion along the top surface of the Cu [85,86].…”

The impact of electromigration in copper interconnects on power grid integrity

“…For thin copper interconnects at nanometer-scale geometries, which are the subject of this work, the primary diffusion paths for void nucleation is along the surface [10]- [13] and grain boundaries play a significant role only in much wider wires that show polycrystalline grain structures. However, once the void nucleates the surface of the void which is an open copper surface acts as a fast diffusion path [12].…”

“…The resistance change distribution can then be expressed as ∆R LogN(µ∆R, σ∆R), where µ∆R = µL void + log kR + log Ro (12) σ∆R = σL void (13) We now summarize the conditions that must be satisfied to achieve a resistance change of ∆R at an observation time to. First, a void must nucleate, and then this nucleated void must grow to the point where the wire resistance increases by ∆R.…”

“…For the first case, the first term, for ∆R for a nucleated void is given by LogN(µ∆R, σ∆R) as derived above, with the mean and standard deviation given by Equation (13). For the second, the nucleation probability is given by LogN(µt n , σt n ) in Equation (6), and this quantity corresponds to the probability that the nucleation time, tn, is less than the observation time, to, i.e., the CDF of tn at to.…”

Diffusivity variation in Electromigration failure

“…A great deal of attention has been paid to the quality of the copper/cap-layer interface (particularly through the introduction of metal caps such as CoWP [4]) as this interface has represented the dominant metal migration path in recent years. At the 65 nm node however, the change in the line microstructure to a bamboopolycrystalline mix necessarily creates an atomic diffusivity which varies with position along the line.…”