Today, the price of building a factory to produce submicron size electronic devices on 300 mm Si wafers is over billions of dollars. In processing a 300 mm Si wafer, over half of the production cost comes from fabricating the very-large-scale-integration of the interconnect metallization. The most serious and persistent reliability problem in interconnect metallization is electromigration. In the past 40 years, the microelectronic industry has used Al as the on-chip conductor. Due to miniaturization, however, a better conductor is needed in terms of resistance–capacitance delay, electromigration resistance, and cost of production. The industry has turned to Cu as the on-chip conductor, so the question of electromigration in Cu metallization must be examined. On the basis of what we have learned from the use of Al in devices, we review here what is current with respect to electromigration in Cu. In addition, the system of interconnects on an advanced device includes flip chip solder joints, which now tend ...

Recent advances on electromigration in very-large-scale-integration of interconnects

This paper provides an overview on the current understanding of electromigration in metals. The discussion is first focused on studies in bulk metals and alloys. This part includes a thermodynamic formulation of electromigration, a kinetic analysis of the atomic processes and a review of the theory. In addition, experimental results in interstitial and substitutional systems are summarised. The second part of the paper reviews the studies in metallic thin films. This emerged as an important area of electromigration studies since the late 1960s when electromigration damage was found to cause failure of conductor lines in integrated circuits. The discussion will review first the basic nature of electromigration in thin films with emphasis on the role of grain boundaries in mass transport and damage formation. Then the materials issues of electromigration will be explored according to the scaling trends in VLSI technology. Finally, the recent results of electromigration in fine lines and device contacts of dimensions in the micrometre range are discussed.

https://iopscience.iop.org/article/10.1088/0034-4885/52/3/002/pdf

Electromigration in metals

An introduction to Cu electromigration

The important integrated circuit failure mechanism of electromigration is reviewed. The basic physics of failure is introduced and the concepts of electromigration and thermally induced stresses are discussed. A concept of thermodynamics in a conducting material and the response to non-direct current will be presented.

Electromigration in integrated circuit conductors

Motions of Microscopic Surfaces in Materials

We have found that the lifetime of aluminum films subjected to high current densities at elevated temperatures can be increased by the addition of copper. Previous studies have indicated that the failure mechanism is a combination of electromigration-induced phenomena, including nucleation and growth of voids, which are gated primarily by material transport along grain boundaries. On the basis of the present study, it appears that the presence of copper causes an appreciable retardation in the rate at which this overall combination of processes takes place, thereby producing a considerable increase in lifetime.

Reduction of electromigration in aluminum films by copper doping

The rate of electromigration in thin films of aluminum and aluminum alloyed with copper has been determined by measuring the changes in resistance of stripes subjected to a current density of 4 × 106 A/cm2. At temperatures in the range from 100 to 200°C the activation energy for electromigration has been found to have the same value for both the pure and the copper-alloyed samples, namely, 0.6 eV. However, the rate of migration is much smaller, by a factor as large as 100, in the copper-bearing samples. These results are discussed in terms of grain boundary diffusion and the effect of alloying additions on diffusion mechanisms.

Activation energy for electromigration in aluminum films alloyed with copper

The composition, phase formation, stress, resistivity, and, in particular, the oxidation and corrosion behavior of Cu-Al films with a variety of Cu:Al ratios have been determined. Their relevance to the gas panel is discussed.

http://ieeexplore.ieee.org/iel5/5288520/5390854/05390864.pdf

F. M. d'Heurle

Papers

Reduction of electromigration in aluminum films by copper doping

Activation energy for electromigration in aluminum films alloyed with copper

Al-Cu alloy for gas panels