In analog integrated circuit (IC) design, it is important to use matched devices, that is, devices designed to have the same electrical properties, to achieve highly accurate circuit performance. Thus, a critical design challenge involves the variability of the individual devices built on the IC. Sources of mismatch include variation in geometrical shapes, poor layout and non-informalities in fabrication process and operating environment. Fabrication processing non-uniformity may be introduced by, for example, mask misalignment and non-uniform etching.
Certain types of devices are very sensitive to neighboring devices. Neighbor interactions can contribute significantly to device mismatch as well.