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The transport of argon ions through the sheath as well as through the neutral region in electron cyclotron resonance discharges in argon gas is studied by means of Monte Carlo simulation, with the emphasis on the sheath potential and the characteristics of argon ions in the sheath. The evolution of the energy, velocity, and angle distributions of the ions in the sheath and the dependence of the distributions on gas pressure and substrate bias are investigated primarily concerned with collisional sheath. It is found that the effect of the pressure on the ion behavior in the sheath is not the same as in the neutral region, however, the substrate bias greatly influences the ion behavior mainly due to ion-neutral elastic collisions within the sheath. Our results also show that the ion motion in crossing the sheath tends to be parallel to the applied magnetic field, and an ion flux with good directionality can be expected by imposing on a negative voltage substrate.

A Monte Carlo method to simulate the plasma characteristics of an electron cyclotron resonance (ECR) microwave discharge system is presented. We use the method to predict the ion behavior in the downstream region of an ECR argon plasma. The pressure and space dependences of the plasma potential, the effects of gas pressure on the ion velocity and angle distribution and the evolution of distributions are examined and discussed in detail. Our results of the simulation show that the ion parallel velocity distribution appears to be bimodal and is strongly dependent on the gas pressure, whereas the ion perpendicular velocity distribution is mainly determined by the applied magnetic field, and the ion beam tends to be parallel to the magnetic field.