Langmuir-probe Characterization of an Inductively-Coupled Remote Plasma System intended for CVD and ALD

We measured electron density and electron energy distribution function (EEDF) vertically through our reactor for a range of process conditions and for various gases. The EEDF of Ar plasma could largely be described by the Maxwell-Boltzmann distribution function, but it also contained a fraction (~ 1E- 03) of electrons which were faster (20-40 eV). At low pressures (6.8-11 μbar), the fast-electron tail shifted to higher energies (Emax ~ 50 eV) as we measured more towards the chuck. The fast-electron tail shifted to lower energies (Emax ~ 30 eV) when we increased pressure to 120 μbar or applied an axial magnetic field of 9.5 μT. Addition of small amounts of N2 (1- 10%) or N2O (5%) to Ar plasma lowered the total density of slow electrons (approx. by a factor of two) but did not change the shape of the fast-electron tail of the EEDF. The ionization degree of Ar-plasma increased from 2.5E-04 to 5E-04 when a magnetic field of 9.5 μT was applied.