The discharge characteristics of low-pressure dual-frequency capacitively coupled argon plasma are investigated through a self-consistent integration of a collisional-radiative model (CRM) and a nonlinear global model. The CRM incorporates 18 excited energy levels, and the electron temperature ( \(\:{\text{T}}_{\text{e}}\) ) and electron density ( \(\:{\text{n}}_{\text{e}}\) ) are determined across a pressure range of 20–70 mTorr by calibrating the emission intensities of the 750.4 nm and 696.5 nm spectral lines. To examine impedance-related effects, an L–π type matching network is experimentally designed and incorporated into the system. The computed values of \(\:{\text{T}}_{\text{e}}\:\) and \(\:{\text{n}}_{\text{e}}\) are then used as input parameters for the global model to analyze plasma current characteristics, including low- and high-frequency electron current components, and the corresponding plasma resistance and inductance, under fixed RF powers of 60 W at 13.56 MHz and 40.68 MHz, respectively, with varying chamber pressures. Fast Fourier Transform (FFT) analysis of the plasma current reveals distinct harmonic features, with pronounced peaks observed not only at the fundamental harmonic, but also at the 2nd, 4th, and 5th harmonic orders. These features are primarily attributed to nonlinear interactions between the plasma sheath and bulk regions, as well as impedance modulation introduced by the matching network. Furthermore, the harmonic structure is closely linked to electron-impact excitation processes between the 1s and 2p levels of argon and their associated reaction rate coefficients. This study establishes a comprehensive coupled modeling framework that connects microscopic excitation dynamics with macroscopic electrical behavior in dual-frequency plasmas, providing theoretical insights into nonlinear discharge mechanisms and valuable guidance for optimizing matching network design.
