Radial magnetic field component plays a key role in determining the plasma density peak location in magnetized capacitively coupled plasmas

Radial plasma uniformity in capacitively coupled plasmas (CCPs) is critical for minimizing variations across the wafer in semiconductor plasma processing. Although magnetic fields have been used to modify plasma profiles, the roles of individual magnetic field components in shaping these profiles remain unclear. Here, magnetic-field-induced plasma profile modification in an argon CCP is investigated using computed tomographic optical emission spectroscopy (CT-OES) and Langmuir probe measurements. In CT-OES, line-integrated optical emission signals acquired from multiple viewing directions are reconstructed into a two-dimensional emissivity distribution, enabling rapid and non-intrusive visualization of the plasma profile. The spatial trends in the reconstructed emissivity distributions are validated by comparison with Langmuir probe measurements. Two single-coil configurations are used to generate distinct radial magnetic field component (Br) distributions. Without an applied magnetic field, the plasma density peak is located near the electrode center. When the magnetic field is applied, the plasma enhancement shifts toward the radial position of maximum Br in both configurations and remains near this position as the coil current is further increased. An opposing-current dual-coil condition displaces the Br maximum without relocating the coils, and the ion density profile forms a broad maximum near the displaced Br maximum rather than near the maxima of the total magnetic flux density (B) or axial magnetic field component (Bz). These results identify the radial position of maximum Br as a practical design parameter for controlling the plasma density peak location in magnetized CCPs.