Stress-aware design methodology

Sub-90 nm CMOS circuits contain a significant amount of mechanical stress in active silicon. This stress is generated by a variety of intentional and unintentional stress sources. Shallow trench isolation is an example of an unintentional stress source, whereas embedded SiGe in the source and drain is an example of an intentional stress source. The amount of stress in each transistor in the circuit depends on the shape of its diffusion area as well as the density of the adjacent layout. The resulting non-uniform stress distribution alters individual transistor performance and, ultimately, the behavior of the circuit. In this paper, several examples are used to illustrate this effect based on design rules for the 45 nm technology node. A number of alternative approaches are suggested for partially suppressing or completely eliminating the stress-induced performance variations.