Multi-channel plasma discharge endpoint detection method
First Claim
1. A method of monitoring a plasma process which comprises(a) optically monitoring a plurality of preselected emission spectra developed by a plasma in a plasma chamber,(b) amplifying and digitizing a plurality of spectra signals of said spectra,(c) weighting and summing said signals to form a composite function, and(d) comparing the slope of the composite function to a predetermined value to determine preselected conditions within said plasma.
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Abstract
A plasma discharge endpoint detection system and method characterized by a plurality of individual data channels which are combined to create a composite function representative of the conditions within a plasma etch chamber. Preferably, a number of the channels are representative of spectral components within the optical spectrum caused by the plasma discharge within the etch chamber. A multi-channel sensor assembly is provided for this purpose including a number of light-guides for guiding light from the plasma discharge to filters and photosensors associated with the multiple channels. Other channels can detect various conditions such as the D.C. bias on a cathode within the plasma etch chamber. The various channels are digitized, weighted and summed within a digital computer to create the composite function from which endpoint and other conditions within the chamber can be determined. The method is characterized by the weighting and summing of a plurality of data channels carrying information about the conditions within a plasma etch chamber to develop a composite function and then analyzing the composite function to determine endpoint and other conditions. The endpoint detection method compares the slope of the composite function to a predetermined maximum slope value and identifies endpoint when the maximum slope value is exceeded a predetermined number of times.
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Citations
12 Claims
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1. A method of monitoring a plasma process which comprises
(a) optically monitoring a plurality of preselected emission spectra developed by a plasma in a plasma chamber, (b) amplifying and digitizing a plurality of spectra signals of said spectra, (c) weighting and summing said signals to form a composite function, and (d) comparing the slope of the composite function to a predetermined value to determine preselected conditions within said plasma.
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6. A method of monitoring the endpoint of a plasma etch process in a plasma etch system which comprises
(a) collecting a plurality of digital emission signals from said plasma, (b) calculating a composite emission curve from said signals by weighting and summing said signals, and (c) determining when the slope of said composite curve exceeds a predetermined slope.
Specification