In situ monitoring and real-time control of gate hardmask etching in high-volume manufacturing of ICs

In the high-volume manufacturing of advanced integrated circuits (ICs), the reproducibility of the gate physical dimension and profile, variation reduction, and control are very important. Continuous running of a gate hardmask etching postprocess switch in fluorocarbon plasma encounters the problems of the gate critical dimension shrinking and the oxide etch rate decreasing as the wafer count increases. To reveal the mechanism and control process shift, optical emission spectroscopy is employed to investigate plasma gas phase and quartz crystal microbalance is employed to investigate real-time polymer deposition on the chamber wall. CF2 concentration in plasma is found being strong, correlating with the polymer coverage amount on the chamber wall. The mechanism of the plasma-wall interaction is illustrated. The successive decrease of polymer on the chamber wall reduces CF2 radical density in plasma, which results in gate critical dimension shrinkage and oxide etch rate reduction. The relative CF2 optical emission intensity is thus proposed to monitor the chamber wall condition and control the gate hardmask critical dimension from run to run to ensure process reproducibility. (C) 2008 The Electrochemical Society.