physical principles, the variety of designs target more specialized processing characteristics. For example, dry etch steps that come into contact with or form critical parts of the device may require higher levels of directionality, selectivity, and uniformity. The tradeoff is that more complex dry etch equipment comes at a higher cost to purchase and is more difficult to understand, more expensive to maintain, and may operate more slowly. Dry etch equipment can control for process uniformity with several knobs. The chuck temperature can be varied to control the heat of the wafer across the radius of the wafer, which influences the rate of reactions and thus the etch rate across different regions of the wafer. The plasma uniformity can be controlled with plasma confinement, which may be controlled with a high speed magnet rotating around the chamber, variations in gas flow into the chamber and pump out of the chamber, or RF braiding around the chamber. These strategies vary per equipment manufacturer and intended application. History Dry etching process was invented by Stephen M. Irving who also invented the plasma etching process. The anisotropic dry etching process was developed by Hwa-Nien Yu at the IBM T.J. Watson Research Center in the early 1970s. It was used by Yu with Robert H. Dennard to fabricate the first micron-scale MOSFETs (metal–oxide–semiconductor field-effect transistors) in the 1970s. See also Plasma etcher Etching (microfabrication) References Semiconductor device fabrication Microtechnology Etching_(microfabrication)