Minghsing Tsai

Reliability of dual damascene Cu metallization

The electromigration (EM) and bias temperature stress (BTS) performances of Cu metallization in dual damascene structure were examined. The experimental results show that Cu has more than one order of magnitude EM lifetime relative to Al alloy. The activation energy of electromigration of Cu trench is 0.9 eV. The failure sites of Cu dual damascene process after EM stress testing are mainly in the bottom of cathode sites vias. Via electromigration can be improved up to one order magnitude by optimizing several processes such as PR stripping, pad structure, etc. BTS study results indicate that the activation energy of Cu ion drift leakage is around 1.1 to 1.4 eV. The interface of capping SiN and SiO/sub 2/ was found to be the major copper diffusion path. Lifetime extrapolated from the empirical data indicates that the device can sustain longer than 1000 years under normal operation condition.

Effect of Cu Line Capping Process on Stress Migration Reliability

Effect of Cu capping layer processes on stress-migration (SM) is discussed in this paper. Cu cap was demonstrated to reduce the failure rates of SM, presumably owing to its suppression of vacancy surface migration under stress gradient. Although formation of CuSix improved the adhesion between copper and dielectric capping layer. Its SM performance was degraded and failure rates increased accordingly. It was hypothesized that introducing silicon into Cu would generate excess vacancies for CuSix process

Design of ECP additive for 65 nm-node technology Cu BEOL reliability

In this work, the design criteria of ECP additives on Cu BEOL reliability are revealed. By varying the ECP additive structures and concentrations, we demonstrate how gap filling performance and impurity level of the bulk copper can influence the electromigration lifetime and stress induced void (SIV) formation. It was found that the impurity in the grain boundary could act as an effective vacancy diffusion barrier to inhibit SIV formation. However, ECP additive conditions that produce highly impure Cu was found to increase the gap filling pits on top of the sub-micron features that would reduce the electromigration (EM) lifetime performance. By proper design of ECP additives, high impurity incorporation in the wide metal line without gap filling pit formation can be achieved. The stress SIV formation was inhibited with excellent EM resistance.