United States Patent Number: 5, 014, 217, May 7, 1991.
NOTE: At the time of publication, the author Richard Savage was not yet affiliated with Cal Poly.
A method and apparatus to control the plasma environment in a semiconductor or thin-film fabrication chamber. The apparatus and method include a means for measuring an optical emission spectrum of the chemical species in the plasma and a library containing a multiplicity of predefined spectral patterns. A processor automatically correlates the spectrum with the predefined spectral patterns in the library, and yields a correlation value for all the correlations. A subset of the predefined spectral patterns based upon the highest correlation values are selected and used to identify the chemical species and abundances thereof in the plasma. A comparator compares the subset with a target set of plasma species and abundances and a control signal generator generates a control signal in response to the comparison to control the chamber environment. In a preferred embodiment, the control signal controls the plasma environment in the reactor chamber when said subset differs from said target set by a predefined amount.
Materials Science and Engineering
Number of Pages
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