Linear magnetron high deposition rate magnet pack for high power impulse magnetron sputtering

High Power Impulse Magnetron Sputtering (HiPIMS) or High Power Pulsed Magnetron Sputtering (HPPMS) is a magnetron sputtering method that has proven to be a promising ionized physical vapor deposition (PVD) technique, with industrial implementation hindered by low deposition rates. HiPIMS applies high voltages and high currents at low duty cycles to the sputtering target in order to achieve very high power densities, causing electron densities near the target to reach three orders of magnitude higher than DC magneton sputtering (DCMS), allowing for an increased ion flux toward the substrate [1]. The increased ionization flux incident on the substrate increasing the coating or film density and quality [2]. HiPIMS has deposition rates have been cited as low as 25% of DCMS deposition rates for relevant target materials [3]. The reasons for the low deposition rate are numerous. The main reasons are the return effect [4,5], the yield effect, and the ion species effect [5]. Although all of these difficulties could be addressed to combat the issue of low deposition rates in HiPIMS, the return effect is the main issue that is addressed by the author. The magnetic field strength, shape, and inclination on the target surface all effect the sputtering yield of the magnetron [6]. Previous studies by Raman et. al [7,8] have shown that a complex magnetic field topology allows for an increased deposition rate in HiPIMS discharges for a 4 inch circular magnetron. To increase the deposition rate, the magnet pack behind the target is altered, and the new magnetic field allows for an increased ion flux by reducing the return effect. In industrial settings, linear magnetrons are more often used than 4 inch or smaller magnetrons. Because HiPIMS is currently not competitive on large scales, there is a demand for a similar magnet pack, but for a linear geometry, scalable to any desired length. Circular magnet packs have complete symmetry, but linear magnet packs do not, causing major issues in the corners of standard magnet packs, where erosion tends to occur much quicker, due to the magnetic field non-uniformity. An investigation of whether a similar magnetic design as the tripack v300 can increase deposition rates in linear systems just the same as in circular geometries [8], is carried out in this work. A magnet pack is designed and modeled in COMSOL Multiphysics, where a magnetic field design similar to the Tripack v300 is implemented on a linear geometry with additional emphasis on controlled electron loss and expanding plasma allowance. The modeled magnet pack is manufactured and named the linear tripack magnet pack. Deposition rate and deposition uniformity measurements for multiple powers are discussed for both DC and HiPIMS, using both a standard linear magnet pack and the linear tripack magnet pack. Additionally, ion fraction, electron temperature, and electron density measurements are taken, and a particle flux model is used to explain the ionization mechanisms in HiPIMS for both the standard and linear tripack magnet pack