Operating Condition: Operating Temperature Variation

8.3. Operating Temperature Variation

Temperature variation is unavoidable in the everyday operation of a design. Effects on performance caused by temperature fluctuations are most often handled as linear scaling effects, but some submicron silicon processes require nonlinear calculations.

Operating Condition: Supply Voltage Variation

8.2. Supply Voltage Variation

The design’s supply voltage can vary from the established ideal value during day-to-day operation. Often a complex calculation (using a shift in threshold voltages) is employed, but a simple linear scaling factor is also used for logic-level performance calculations.

Operating Condition: Process Variation

8.1. Process Variation

This variation accounts for deviations in the semiconductor fabrication process. Usually process variation is treated as a percentage variation in the performance calculation. Variations in the process parameters can be impurity concentration densities, oxide thicknesses and diffusion depths. These are caused bye non uniform conditions during depositions and/or during diffusions of the impurities. This introduces variations in the sheet resistance and transistor parameters such as threshold voltage. Variations are in the dimensions of the devices, mainly resulting from the limited resolution of the photolithographic process. This causes (W/L) variations in MOS transistors.