Production of low electron temperature ECR plasma for thin film deposition

An electron cyclotron resonance (ECR) plasma with low electron temperature parallel to the magnetic field was produced by applying the mirror magnetic field for Ar, Ar/N₂ and H₂ gasses. It was found that the temperature parallel to the magnetic field was lower than the temperature perpendicular to the field by 5 ∼ 50% and decreased at the 'throat' of the mirror magnetic field. Especially, the electron temperature parallel to the magnetic field was observed to be less than 2 eV in the Ar/N₂ and the H₂ plasma. Our experimental results suggested that the high-quality thin films could be prepared by setting the substrate perpendicular to the field lines at the 'throat' of mirror magnetic field because of the decrease in ion bombardment to the substrate.