Position Control in Lithographic Equipment [Applications of Control]

Abstract

Lithographic steppers and scanners are highly complex machines used to manufacture integrated circuits (ICs). These devices use an optical system to form an image of a pattern on a quartz plate, called the reticle, onto a photosensitive layer on a substrate, called the wafer. The circular wafer, having a diameter of 200 or 300 mm, is usually made of silicon. Since one wafer can contain many ICs, typically 100 or more, the wafer needs to be repositioned from exposure to exposure. Exposure itself takes place during a scanning motion of the wafer and the reticle.