Method and apparatus for optical emission end point detection in plasma etching processes

A method for determining the time at which a plasma etching process should be terminated, said process generating at least one discrete plasma species indicative of the progress of said process and a contniuum plasma emission, comprising:

• monitoring the optical emission intensity of said plasma in a narrow band centered about a predetermined spectral line and generating a first signal indicative of the spectral intensity of said plasma species;
• monitoring the optical emission intensity of said plasma in a wide band distinct from said narrow band and the emission spectral line of any discrete plasma species and generating a second signal indicative of the spectral intensity of only said continuum plasma emission;
• monitoring the magnitudes of said first and second signals and generating a termination signal when said magnitudes diverge;
• and
• indicating when said plasma etching process should be terminated in response to said termination signal.

An apparatus for determining the time at which a plasma etching process should be terminated, said process generating at least one plasma species indicative of the progress of said process comprising:

• means for monitoring the optical emission intensity of said plasma in a narrow band centered about a predetermined spectral line and generating a first signal indicative of the spectral intensity of said plasma species;
• means responsive to changes in an electrical property of said plasma for generating a second signal indicative thereof;
• and
• means for monitoring the magnitudes of said first and second signals and generating a termination signal when said magnitudes diverge, thereby indicating when said plasma etching process should be terminated.