A wafer is a thin circular slice of semiconductor material, often silicon, used to make discrete semiconductor devices and integrated circuits (chips). A wafer is typically less than 1 mm thick and its diameter can range typically from about 75 mm to 300 mm. Wafers are made by slicing a cylindrical ingot of single crystal semiconductor material. Using lithography, many chip patterns are printed onto the wafer, and the wafer is diced into individual chips.

The part of a lithography system used to rapidly and accurately position the wafer tables carrying silicon wafers. In a TWINSCAN™ system, wafers are simultaneously positioned under the lens and a measurement system for pre-alignment.

The wavelength or color of light radiation used in photolithography systems. The wavelength determines the minimum feature size that can be printed on chips – shorter wavelengths print smaller features. The wavelengths in recent years have shortened from 365 nanometers (older generation = I-line) to 248 nm (KrF technology) to 193 nm (ArF technology). EUV will use a 13.5 nm light source.