Stress Driven Diffusive Voiding of Aluminum Conductor Lines: A Model for Time Dependent Failure.

摘要

Cracking or voiding of passivated aluminum conductor lines in integrated circuits has been observed by many workers since 1984. This problem has been brought on by the trend in the microelectronics industry to miniaturize circuitry. Most reports on the subject attribute the cause to diffusion creep. This report points out certain difficulties with this conclusion and presents the essential features of a related failure mechanism which is termed ''constraint cavitation.'' A numerical stress analysis is presented to illustrate stress gradients and their sources. These stress gradients are known to drive mass transport which leads to void formation. Equations are presented which describe the growth rates of two void morphologies. A definition of failure is made and the time to failure is calculated and the relationship with line width and temperature is given. With properties of aluminum taken from the literature, it will be shown that the calculated failure time is in very good agreement with experimental data. 71 refs., 36 figs., 4 tabs. (ERA citation 14:001467)