Void formation in a copper-via-structure depending on the stress free temperature and metallization geometry

authored by

Kirsten Weide-Zaage, David Dalleau, Yves Danto, Helene Fremont

Abstract

The understanding of degradation phenomena in dual-damascene (DD) copper metallization structures due to high current densities and temperatures in reliability stress tests has been an important challenge during the past decades. Compared to standard Al(Cu)-based and W-plug interconnects for copper as metallization material the failure mechanism might change caused by the different architecture of a DD interconnect system. The determination of the mass transport pathway is one major point of concern. Electromigration for instance can occur through a number of different pathways like the surface, the interface, and the grain boundaries. In a DD copper metallization, interface diffusion was determined as main degradation mechanism. Beside the electromigration due to the joule heating, temperature gradient driven thermomigration will occur. Out of the mismatch between the properties of the different materials in the DD interconnect like thermal expansion coefficient (TCE) mechanical stress in the metallization system arises. Out of this the reliability prediction due to the different migration mechanisms like electro-thermo- and stressmigration as well as the different migration path become more and more important and have to be considered. In this study the void formation, as well as the mass flux divergence distribution out of the static simulations, in a copper metallization was investigated by finite element simulation (using ANSYS®). A calculation routine is used for the determination of the mass flux divergences and void formation in the model. First the suitability of the simulation will be shown by the calculation of the void formation for a copper interconnect structure taken from the literature. For comparison of the different influences default models were created. Based on the default models the overlap of the metallization, the via height, the applied current density and stress free temperature was varied. The mechanical stress, the temperature and current density distribution as well as the influence of the different migration mechanisms were determined. Out of this the void formation and its localisation were calculated.

Organisation(s)

Laboratorium f. Informationstechnologie

External Organisation(s)

Universite de Bordeaux

Type

Conference contribution

Pages

367-372

No. of pages

6

Publication date

2004

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Engineering(all)