SELECTION OF WAVELENGHTS FOR END POINT IN A TIME DIVISION MULTIPLEXED PROCESS

摘要

The present invention provides a method for establishing endpoint during an alternating cyclical etch process or time division multiplexed process. A substrate is placed within a plasma chamber and subjected to an alternating cyclical process having an etching step and a deposition step. A variation in plasma emission intensity is monitored using known optical emission spectrometry techniques. A first wavelength region is selected based on a plasma emission from an etch by product and a second wavelength region is selected based on a plasma emission from a plasma background. A ratio of the first wavelength region to the second wavelength region is computed and used to adjust the monitoring of an attribute of a signal generated from the time division multiplex process. The alternating cyclical process is discontinued when endpoint is reached at a time that is based on the monitoring step.