Effect of Magnetic Pole Alignment in Hybrid Multi-Cusp Magnetic Fields on Hydrogen Plasma Behavior in an RF-Powered Hollow Cathode Discharge

This study investigates the influence of magnetic pole alignment in hybrid multi-cusp magnetic field (HMCMF) configurations on hydrogen plasma behavior within an RF-powered hollow cathode cylindrical capacitively coupled plasma (CCP) system. Two configurations—configuration-X (anti-pole aligned) and configuration-Y (like-pole aligned)—were compared under identical discharge conditions: 50 W RF power at 13.56 MHz with hydrogen gas pressures of 3 Pa, 1 Pa, and 0.7 Pa. Plasma density was measured using a Langmuir probe biased at –70 V DC across radial (0–80 mm) and axial (-30 to 35 mm) positions. The chamber was divided into three analytical regions: R1 (inner groove), R2 (transition), and R3 (downstream expansion). Characterization included 3D magnetic field analysis, discharge voltage, optical emission, plasma density, spatial uniformity (U), and plasma uniformity factor (PUF). Results show configuration-Y significantly improves confinement and uniformity, especially at low pressures. At 0.7 Pa in R3, plasma density increased by 94% (average) and 95% (maximum), with uniformity enhancements of 97% (U) and 118% (PUF) compared to configuration-X. These findings highlight the critical role of magnetic pole orientation in plasma stability and transport. The outcomes offer valuable insight for optimizing CCP systems used in surface engineering, semiconductor processing, and potentially negative ion sources.