Thermally Induced Failure of Microelectronic Structures

Abstract

The purpose of this paper is to perform a theoretical evaluation to assess mechanical failure of an idealized two-dimensional, narrow, thin microelectronic structure, modelled as a plate, composed of a homogeneous, isotropic, linear-elastic material. The proposed steady-state model examines the effects of imposing a constant-uniform-uniaxial mechanical load, whose magnitude is a fraction of the yield strength of the material at room temperature, on a plate with an existing thermal stress profile generated by a gaussian temperature gradient across the plate width. The temperature dependence of the mechanical properties of the material requires that a new approach to failure evaluation be implemented. The model shows that failure can occur anywhere in the cross-section of the plate and at loads well below the yield strength of the material at room temperature, depending on the particular conditions which the plate experiences. These preliminary results may find applicability in the evaluation of microelectronic structures, e.g., a silicon chip mounted on a substrate and subjected to convective cooling due to fluid (gas or liquid) flow in a preferred direction. Resulting thermal gradients and stresses, in conjunction with mechanical loading generated from thermal expansion mismatch between the chip and the substrate, may cause component failure.