This is just an Excerpt from a larger document, click here to view the entire document.Qualification Based on Failure Mechanism
It is a matter of great complexity to build a system lifetime model to fit all temperatures and voltages if there are multiple failure mechanisms involved. The conventional extrapolation method using one EaSYS and γSYS tends to give an optimistic estimation. For reliability qualification considering multiple failure mechanisms, acceleration tests should be designed to accelerate the target failure mechanism with specific stress conditions. This is workable because each failure mechanism has its unique activation energy and voltage acceleration parameter. Among these failure mechanisms, only HCI has negative activation energy while others' are positive. This means lowering stress temperature will accelerate HCI while decelerating the other three failure mechanisms. HCI also has a comparable large γ, so at low temperature and reasonable high voltage, HCI failure will dominate. For EM, since the copper interconnect has a larger activation energy and small γ(< 2), acceleration tests should be designed with high temperature and low voltage. Traditional acceleration tests with high temperature and voltage can be applied to accelerate TDDB and NBTI since both have large voltage acceleration parameter and activation energy. The failure percentage of each failure mechanism at various accelerated conditions is shown in Fig. 3.
Figure 3. Failure percentages of EM, HCI, TDDB and NBTI at different accelerated conditions. (Click to Zoom)