Abstract
The correlation of RF impedance with Ar plasma parameters was analyzed in semiconductor etch equipment using inductively coupled plasma. Since the impedance measured by a VI probe installed behind the RF bias matcher had information for plasma and structural parts of chamber simultaneously, the impedance was corrected by excluding transmission line and peripheral parts of the bias substrate. The corrected impedance was compared with plasma parameters, such as plasma density and electron temperature. The coefficient of determination between the corrected plasma resistance and the theoretical formula of the resistance for bulk plasma was over 0.9 unlike the resistance measured by the VI probe. It is expected that the corrected RF impedance can assist in monitoring the status of plasma and maintaining the quality of the etch process in semiconductor mass production lines.
Highlights
The difficulty of the plasma etch process in the semiconductor industry has gradually increased because the structures of semiconductor chips have become more complicated
The bias power was defined as the measured power by the VI probe same as the power supplied from the RF bias generator minus the power consumed by the RF bias matcher because the bias matcher consumed the power nonlinearly as the supplied power increased
We investigated the correlation of RF impedance with Ar plasma parameters in a plasma etch chamber
Summary
The difficulty of the plasma etch process in the semiconductor industry has gradually increased because the structures of semiconductor chips have become more complicated. Process engineers have tried to find a completely optimized plasma etching recipe for the complicated structures based on the experience obtained in trial and error and the knowledge of the basic chemistry and physics of the plasma process.. Process engineers have tried to find a completely optimized plasma etching recipe for the complicated structures based on the experience obtained in trial and error and the knowledge of the basic chemistry and physics of the plasma process.1 Basic plasma parameters, such as electron density, electron temperature, and DC bias voltage, are useful to understand the plasma etch process and to determine the proper recipe. It is impossible to directly measure the plasma parameters during the plasma etch process by using an invasive plasma monitoring method because inserting a probe into an industrial process chamber is disallowed. In “Sec. III,” as source power, bias power, and process pressure were varied, correlations of the corrected RF impedances with Ar plasma parameters are presented.
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