Design and Strategy for Reliability in ICs

Over 20 years ago I was asked to perform a Reliability Qualification on a finished product, almost as an afterthought - a necessary evil to make the product saleable ! These days most of us expect to perform qualification work on first silicon, and to have done some kind of peer review on the design before tape out.

But when exactly in the product creation process should the Reliability function become involved? I would expect most people these days to answer, "In the design phase", but we really need to start earlier than that - at the study phase. The whole process of Design for Reliability (DfR) and Design for Analysis (DfA) begins at the stage when we are considering such seemingly trivial aspects as the package to be used, and the most appropriate library and process for design.

Then of course there is the design phase. It is common practice for many organisations to have a check list for Reliability issues prior to tape out. However, the Reliability function can get involved much earlier than that - influencing the choice of IP, defining DfR rules, and helping to apply these rules.

The Knowledge Based approach to Reliability Qualification means that we not only run a programme of Stress Tests, but also make use of Structural Similarity and Generic Data. The interpretation of our Stress Test results is dependent on our ability to understand the nature of failures. If we have adopted the right approach to DfA and DfT then the process of electrical diagnosis and Failure Analysis will be so much easier.

It is important to appreciate how many of the activities I have described are inter-related. In a culture of increased outsourcing there is a risk of separating out these functions with potentially disastrous results. For this reason it is important to involve Reliability throughout the product creation cycle from study phase through to the end product.

The application of Data Review and Risk Analysis to this process allows focus on Key Risks, reduction of Operational Costs, and an improved Time to Market. Apart from the logistical and technical advantages of this approach, in the current economic climate it provides a route to cost reduction and in my view this will be the key driver of this methodology.