A practical approach to modeling product performance degradation and assigning lifetime reliability guard band

Transistor degradation over time due to hot carrier injection (HCI) and bias temperature instability (BTI) is known phenomenon. The common approach to ensure reliability over the product lifetime is to provide a guard band. Applying technology level transistor degradation results directly to product is a pessimistic approach that can result in an unnecessary penalty when trying to meet product performance specifications. In this paper we will describe an approach to measure product parametric degradation over time that can be modeled to accurately assign reliability guard bands at nominal field conditions. This work also investigates process and design sensitivities to product degradation. Units are stressed running benchmark pattern at stress condition and resulting degradation is mathematically modeled to nominal field conditions and lifetimes. Experimental correlation of product degradation to voltage, temperature, time, n/p ratio, and measuring voltage is demonstrated.