THERMAL FAILURE IN SEMICONDUCTOR-DEVICES

A first principles approach to the problem of thermal breakdown in semiconductor devices is developed using Green's function formalism. The problem of thermal runaway at a defect of arbitrary geometry, subject to an arbitrary power profile, is considered. A solution is presented for the specific case of a rectangular parallelepiped shaped defect, subject to constant input power. It is expected that this geometry will model the defect in many semiconductor devices more accurately than the defect geometries used in the past. Unlike previous work, this allows all three dimensions of the defect to take on the full range of values. The theory developed here provides a natural framework for the explanation of results previously reported in the literature. It is shown that there are four time domains and not three as previously thought, and these exist for all shapes of defect. Thus, it is wrong to conclude that a pulse power/time to failure dependence of the form Pfα tf- 1 2 necessarily implies a roughly two-dimensional defect. Several relationships are found to exist within the model which allow estimates to be made of the defect dimensions and failure temperature. Experimental data drawn from the literature, produce Pf/tf profiles similar to those indicated by the theory. © 1990.