Failure causes generating aluminium protrusion/extrusion

Abstract

Aluminium protrusion/extrusion are frequent failures, which are responsible for severe short damage in semiconductor devices. Unfortunately, the mechanisms results also frequently as an artifact of many other high-current failure signatures as EOS, which makes root cause investigations sometimes rather difficult. To overcome the problem, most frequent root causes for aluminium protrusion/extrusion are shown and discussed in this paper. This information combined with the individual device process- and testing history helps to conclude to the failure root cause. The authors evaluated and reviewed related case studies of their own practice resulting in following root causes for aluminium protrusions and extrusions: laser-induced damage, ESDFOS, application-related EOS, thermal cycling, thermomechanical mismatch in stacked devices, ultrasonic-induced damaging, micro-Si-particles in chip-pick&place and surface-pressure-induced damage, as for instance when doing copper-wirebonding.