Position control in lithographic equipment

Abstract

In IC manufacturing, lithographic scanners expose a circuit pattern onto a semiconductor wafer by means of an optical system. The stage holding the wafer must have a scanning position accuracy of only a few nanometers to support imaging and overlay requirements. In the past 10 years, stage acceleration, position error and settling time have all improved 5-8 times. Compared to lithographic steppers of 25 years ago, the number of controlled stage axes has grown from 3 (analog) to 50 (high-speed digital).