Study of electromigration mechanisms in 22nm half-pitch Cu interconnects by 1/f noise measurements

The electromigration (EM) performance of Cu interconnects with different barrier/liner combinations is studied by means of 1/f (or generally known as low-frequency) noise measurements. It is shown that Cu interconnects with a TaN barrier and Co liner have lower EM activation energies for 22nm half-pitch line-widths than Ru based liners. Indeed, interconnects with a 1nm Ru liner (both with TaN and Mn-based barriers) are found to outperform lines with a Co liner in terms of EM reliability. A possible explanation for this is a less defective Cu/Ru interface as compared to Cu/Co.