Correlational Study Between SiN Etch Rate and Plasma Impedance in Electron Cyclotron Resonance Plasma Etcher for Advanced Process Control

The correlation between the change in the etching rate of SiN and the change in the monitored plasma impedance was investigated to estimate the capability of critical dimension (CD) prediction with a plasma impedance monitor (PIM). The results obtained with the PIM were compared with those of optical emission spectroscopy (OES), which was performed using the emission intensity ratio of C2/H, and showed that the SiN etching rate is strongly correlated with several values obtained with the PIM. We conclude that the PIM has the potential to predict CDs with the same accuracy as that of OES.