Methods and apparatus for determining an etch endpoint in a plasma processing system

摘要

Methods and apparatus for ascertaining the end of an etch process while etching through a target layer on a substrate in a plasma processing system which employs an electrostatic chuck. The end of the etch process is ascertained by monitoring the electric potential of the substrate to detect a pattern indicative of the end of the etch process. By the way of example, changes to this potential may be observed by monitoring the current flowing to the pole of the electrostatic chuck. Upon ascertaining the pattern indicative of the end of the etch process, for example by monitoring the current signal, a control signal is produced to terminate the etch. If a bias compensation power supply is provided to keep the currents flowing to the poles of the electrostatic chuck substantially equal but opposite in sign throughout the etch, the compensation voltage output by the bias compensation power supply may be monitored for the aforementioned pattern indicative of the end of the etch process in order to terminate the etch.