Abstract
Uniformity has always been a key issue for the dry etching process. However, studies of spatial distributions of plasma in a real etcher are scarce. In this study, spatial distributions of plasma and radicals were investigated using a periscope optical sensor. The distributions of HBr/Cl2/O2/Ar plasma were measured in a UHF plasma gate etcher. Spatial structures of plasma were studied, and a correlation between Ar emission intensity and ion saturation current distributions was found. The results revealed a ring-shaped generation of plasma under the top shower-plate and a change in the diameter of the ring depending on the magnetic field strength or gas pressure. The transport of supplied gas and produced etchant radicals was also studied by monitoring the distributions of Cl and Cl2+. Collisions with background gases diffuse the supplied gas plume and increase the dissociation of the supplied gas. This knowledge will enable tuning the etching process uniformity more easily.
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