Reduction of Particle Contamination in Plasma-Etching Equipment by Dehydration of Chamber Wall

The mechanism of particle generation is investigated in order to prevent defects formed on wafers in the plasma etching of multi-layered films composed of tungsten silicide (WSi) and polycrystalline silicon (poly-Si). Particles are measured by an in situ monitoring system using laser light scattering during the etching process. The particles are composed of AlF3, which is presumably generated by reacting the coating material Al2O3 on the etching chamber wall with plasma containing fluorine atoms, F in the presence of H2O absorbed into the chamber parts and materials. We demonstrated successfully that dehydration of the chamber parts and materials by plasma discharge suppresses particle generation.