Enhancing plasma uniformity in SiH4/NH3 capacitively coupled plasmas via dielectric structure adjustment positioning adjacent to the power electrode

A two-dimensional axisymmetric fluid model was implemented in COMSOL Multiphysics to study the plasma characteristic in radio frequency capacitively coupled SiH4/NH3 plasmas, generally using for deposition of silicon nitride films. The model fully resolves coupled multiphysics (electric-thermal-fluid-plasma interactions), enabling systematic analysis of plasma density uniformity modulation via dielectric structures near the radio frequency-powered upper electrode. By varying the thickness of this dielectric structure, the electric field at the electrode edge can be significantly modified, thereby modulating both the generation rate and spatial distribution of electrons and radicals. Interestingly, when substantial gas flow is introduced, while the electron density distribution remains unchanged, the radical distribution undergoes significant modification. Moreover, the thickness-dependent dielectric structure geometrically constricts the electrode edge gap, accelerating local gas flow and consequently modifying radical transport. This interdependence necessitates coupled optimization of flow patterns and structural parameters for uniformity control.