Optimization of plasma uniformity in inductively coupled Ar/O2 discharges via coil configuration regulation

Inductively coupled plasmas (ICPs) operated with reactive gas mixtures are essential for semiconductor fabrication, yet achieving optimal spatial uniformity remains a significant challenge. In this study, a two-dimensional fluid model is employed to systematically investigate the regulation of plasma uniformity in Ar/O2 inductively coupled discharges through tailored coil configurations. The effects of both horizontally and vertically arranged coil positions (Rhc and Rvc) and number (Nhc and Nvc) on the spatial distributions of electron density and key reactive species are examined. Results reveal that the coil arrangement fundamentally determines the profiles of the azimuthal electric field and inductive power deposition, thereby dictating electron heating dynamics and active species generation. Specifically, coil placement near the chamber center (Rhc=2 cm) or extreme edge (Rhc=27 cm) is unfavorable, as these regions induce weak azimuthal electric fields. With a fixed reference coil at R=23 cm, shifting a secondary coil outward transforms the electron density profile from center-peaked to edge-peaked. The peak densities of neutral species follow this radial migration, though their distributions are additionally modulated by species-dependent diffusion lengths. Vertically stacked coil configurations (increasing Nvc) effectively elevate local plasma density, particularly at smaller radii (Rvc=9 cm), but typically compromise radial uniformity, with density gains saturating as either Rvc or Nvc increases. Introducing additional coils between two fixed positions (increasing Nhc) creates a pronounced inductive electric field maximum beneath the central coil, promoting localized density peaks and further degrading uniformity. Notably, source power and gas mixing ratio exert only marginal impacts on plasma uniformity, yet they offer effective leverage for tuning active species concentrations. In contrast, operating pressure exerts a dominant influence on spatial homogeneity, with lower pressures being strongly conducive to uniform distributions. These findings establish a robust optimization framework for independently controlling the density and uniformity of target species in reactive ICP discharges, offering guidance for advanced semiconductor processing applications.