Process Control: Modeling, Design, and Simulation

M14.2. Reactive Ion Etcher

An important process in semiconductor device manufacturing is plasma etching (or reactive ion etching). In this unit operation, reactive ions are used to selectively remove (etch) layers of solid films on a wafer. A major objective of a control system is to achieve relative etch rates (angstroms/second) by manipulating the process inputs. Currently, etch rate measurements are not readily available, so it is assumed that by measuring and controlling other variables, good control of the etch rate can be obtained.

Two variables important to control are the voltage bias of the plasma and the fluorine concentration, since they ultimately determine the etch rate. Two important manipulated variables are the RF power and the ...