End point detection method for plasma etching of semiconductor wafers with low exposed area
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United States of America Patent
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Jan 18, 2011
Grant Date -
Jul 20, 2006
app pub date -
Jan 18, 2006
filing date -
Jan 19, 2005
priority date (Note) -
Expired
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Abstract
A method for controlling the plasma etching of semiconductor wafers determines the impedance of a plasma chamber using values representing voltage, current, and the phase angle between them, as provided by a sensor. All or less than all of the data during a first time period may be used to calculate a model. During a second time period, real time data is used to calculate a version of the instant impedance of the chamber. This version of impendence is compared to a time-projected version of the model. The method determines that etching should be stopped when the received data deviates from the extrapolated model by a certain amount. In some embodiments a rolling average is used in the second time period, the rolling average compared to the model to determine the end point condition.
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