First, the method to calculate Coulomb collisions in materials processing plasmas is presented. Next, by use of the method, the effect of electron-electron (e--e-) collisions on the relaxation of electron energy distribution function (EEDF) is examined for a spatially uniform argon plasma. The EEDF is shown not to tend to the Maxwellian distribution without e--e- collisions because once high-energy electrons lose energy by inelastic collisions, they have no chance to recover their energy without e--e- collisions. When e--e- collisions are taken into consideration, the relaxation time of the EEDF at gas pressure 10 mTorr is 40, 20, and 10 μs for electron densities 10l6, 1017, and 1018 m- 3 respectively. Lastly, the effect of e --e- collisions on the EEDF is examined for a capacitively coupled plasma at gas pressure 25 mTorr. It is found that the effect is negligible even for the electron density 1017 m - 3.
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