Cu-Induced Dielectric Breakdown of Porous Low-Dielectric-Constant Film

Dielectric breakdown induced by Cu ion migration in porous low-k dielectric films has been investigated in alternating-polarity bias conditions using a metal–insulator–metal capacitor with Cu top metal electrode. The experimental results indicated that Cu ions migrated into the dielectric film under stress with positive polarity, leading to weaker dielectric strength and shorter time to failure (TTF). In the alternating-polarity test, the measured TTFs increased with decreasing stressing frequency, implying backward migration of Cu ions during reverse-bias stress. Additionally, compared with a direct-current stress condition, the measured TTFs were higher as the frequency was decreased to 10−2 Hz. The electric-field acceleration factor for porous low-k dielectric film breakdown in the alternating-polarity test was also found to increase. This Cu backward migration effect is effective when the stressing time under negative polarity is longer than 0.1 s.