Application of chemometrics to optical emission spectroscopy for plasma monitoring

摘要

Abstract: Real-time plasma etch process monitoring, based onsensors which measure plasma properties that relatedirectly to desire etch features, is critical to themanufacturability of future- generation integratedmicroelectronics. This study reports on the developmentof spatially resolved optical emission spectroscopytools and spectral signature analysis techniques which,taken together, show promise for meeting the need forsuch a sensor- based tool. This approach to plasmamonitoring requires the development of optical emissioncalibration data sets, which in this case were obtainedusing the GEC Reference Cell plasma etch reactor (a RIERF discharge system developed for interlaboratorycomparisons). Systematic electrical probe measurementsof the current and voltage waveform characteristics ofAr and CF$- 4$//CHF$-3$/ discharges in the Cell arereported and shown to be a sensitive indicator of bothvariations in Cell to Cell characteristics andprocess-induces variability within a Cell. Variationsin the optical emission intensity show a near unitycorrelation with probe measurements if a broad spectrumof the emission is examined using multivariatestatistical algorithms (chemometrics) and the spatialdependence of the emission is considered. Preliminaryresults involving further application of this spectralsignature analysis technique to silicon dioxide etchingare discussed.!13