Low-Frequency Noise Measurements for Electromigration Characterization of Cu Interconnect Under Metal Barrier Punch Through Process Optimization

This paper demonstrates the variation in electromigration (EM) reliability of Cu interconnect during punch through (PT) process optimization in BEOL. By using a relatively new test methodology based on low-frequency noise (LFN) measurements, the EM reliability of Cu wires with various bottom profiles under different optimization circumstances were discussed. The main advantages of LFN over the standard accelerated EM tests are that they are non-destructive, much faster, much cheaper, and closer to operation conditions. With the LFN technique, we find out that under metal barrier PT Process optimization, the metal lines with better cross section profiles tend to have better early EM characteristic.