Influence of the edge effect of the solenoid magnetic field on the discharge process of magnetron sputtering in long and narrow chambers
Sep 19, 202414 pages
Published in:
- JINST 19 (2024) 09, P09027
- Published: Sep 19, 2024
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Abstract: (IOP)
The fourth-generation light source or future particleaccelerators have compact vacuum systems, resulting in a small flowconductance of the beam chamber. The development of NEG(Non-Evaporable Getters) films technology with distributed pumpingis a good solution. This technology can obtain a pressuredistribution with a small pressure gradient and an ultra-high vacuumof 10 Pa inside the vacuum chambers. In the magnetronsputtering process for NEG coating, the inhomogeneity of themagnetic field at the edge of the solenoid is a key parameter foraffecting the stability of the magnetron sputtering dischargeprocess. The influence mechanism of the edge magnetic field on theplasma discharge process and discharge uniformity was studied tooptimize the coating parameters, which is very important. TheParticle-In-Cell/Monte Carlo Collision (PIC/MCC) method was employedto simulate plasma discharge in a narrow vacuum chamber undervarious edge magnetic field conditions. The potential distribution,charged particle density distribution, and particle densitydistribution on the target were acquired for four sets of dischargeparameters, followed by data processing and analysis. The electricfield distribution during the discharge process is closely linked tothe non-uniformity of the magnetic field at the solenoid's edge. Thesmaller Br (the radial component of the magnetic field) component ofthe magnetic field, the more uniform distribution of Ar on thetarget surface, and the smaller the difference along the length ofthe vacuum chamber. A smaller radial component (Br) of the magneticfield results in a more uniform distribution of Ar on thetarget surface and reduces variations in film thickness along thelength of the vacuum chamber. This is attributed to the smalldistance between the inner wall of the vacuum chamber and thecathode target. The change in the edge magnetic field will result inthe rapid migration of electrons to the inner wall of the vacuumchamber and insufficient collision with the discharge gas, making itchallenging to sustain the discharge process. Moreover, fluctuationsin the edge magnetic field of the solenoid induce gradient drift andcurvature drift in charged particles, resulting in rapid electronloss and alterations in the density and potential distribution ofcharged particles at the ends of the vacuum chamber, ultimatelyleading to discharge instability. The research results show theimportance of the edge magnetic field effect on the magnetronsputtering coating of the slender vacuum chambers, which provides animportant reference for the segmented coating process of similarvacuum chambers in future accelerators.- Instrumentation for particle accelerators and storage rings - high energy (linear accelerators, synchrotrons)
- Instrumentation for synchrotron radiation accelerators
- Nuclear instruments and methods for hot plasma diagnostics
- Plasma generation (laser-produced, RF, x ray-produced)
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