Design of circular composite sputtering cathode and simulation of its discharge characteristics

Abstract

Based on the two-dimensional finite element method, the magnetic field of circular composite magnetron sputtering cathode is calculated by COMSOL software. The genetic algorithm and simulated annealing algorithm combined with Matlab optimization toolbox are used to optimize the structure of circular composite magnetron sputtering cathode, and the structural parameters with the largest utilization rate of target are obtained. For the resulting optimized magnetron cathode, based on the self-consistent particle simulation method, the discharge characteristics under different working conditions are simulated by VSim software. It is found that with the increase of non-equilibrium degree of magnetic field, the cathode surface potential drops to the maximum position and the location of the plasma aggregation, moving from the outer surface of the cathode to the center, the intensity of the magnetic field on the cathode surface decreases When the two coils have no currents flowing, the density of the plasma is largest and the thickness of the sheath is smallest In the two coils there flow reverse 5 A currents, the non-equilibrium magnetic field reaches a maximum value and the thickness of sheath is largest, the corresponding electric field strength is weak, which is not conducive to the impact ionization, so the plasma density is smallest However, in the two coils there flow positive 5 A currents, and the non-equilibrium magnetic field is smallest, the plasma density and the sheath thickness are not only related to the non-equilibrium magnetic field, but also to the magnetic field strength. Finally, according to the results of particle simulation, the target erosion depth of the magnetron cathode is studied. Combined with the sputtering yield curve, the curve of etching depth of the cathode target surface is obtained. It is found that the erosion range of the target extends from 60 mm to 76.2 mm (target radius) before and after optimization. By adjusting the magnitudes and directions of currents in the two coils, all the target surfaces can be etched, which greatly improves the target utilization.