Photoresist etching in an inductively coupled, traveling wave driven, large area plasma source

We report on experimental and modeling results for photoresist etching with oxygen gas in an inductively coupled large area plasma source (LAPS). The source is driven by a 13.56 MHz traveling wave launched along a serpentine antenna embedded in the plasma and has a processing area as large as 40 cm×50 cm. We describe a new series-parallel antenna coil configuration, and we present experimental observations for oxygen plasma density profiles, photoresist etch rates, and etch profiles. We introduce a simplified spatially varying oxygen discharge model corresponding to a two-dimensional LAPS geometry in order to account for the generation and loss of both etchant atoms (O atoms) and bombarding ions. The model and experimental results on plasma density are compared. A simplified photoresist etch kinetics model combined with the spatially varying oxygen discharge model is then described. The ion flux and O-atom density predicted by the model are compared with the etch rate data. In order to gain insight into the underlying physical mechanism, we also compare the data with the scaling behavior of the etch rates predicted by a volume-averaged (global) oxygen discharge model. The models and experimental results are generally in good agreement.