Modeling of wave heated discharges used in plasma processing reactors

Magnetically enhanced inductively coupled plasma (MEICP) and helicon plasma sources typically have a higher plasma density for a given power deposition than conventional inductively coupled plasma (ICP) sources. In industrial plasma sources where magnetic fields typically span a large range of values and modes are likely not to be pure, power deposition likely has contributions from both noncollisional heating and electrostatic damping. Mechanisms for power deposition and electron energy transport in MEICPs have been computationally investigated using 2-D and 3-D plasma equipment models. In the 2-D model, 3-D components of the inductively coupled electric field are produced from an m = 0 antenna and 2-D applied magnetic fields. These fields are then used in Monte Carlo simulations to generate electron energy distributions (EEDs), transport coefficients, and electron impact source functions. The electrostatic component of the wave equation is resolved by estimating the charge density using a oscillatory perturbed electron density.; Results for process relevant gas mixtures are examined, and the dependence on magnetic field strength and field configuration is discussed. Standing wave patterns in the electric fields result in power deposition within the volume if the plasma. As the static magnetic field is increased, the electric field propagation follows magnetic flux lines, and significant power can be deposited downstream. However, the ability to deposit power downstream is limited by the wavelength of the helicon wave, which depends on the plasma density. If the plasma is significantly electronegative in the low power-high magnetic field regime, power deposition will resemble ICP behavior.; Collisional damping may be the dominant heating mechanism at moderate pressures (>2 mTorr). However, at lower pressures, where resonant electrons have velocities near the wave phase velocity, Landau damping may be an important heating mechanism. Landau damping may occur over a broad range of energies (10–100 eV), in contrast to earlier predictions of narrow energetic beams.; The tails of the EEDs are enhanced in the downstream region, indicating some amount of electron trapping. This results from noncollisional heating by the axial electric field for electrons which have long mean-free-paths. Results indicate that the effect of the electrostatic term in Maxwell's equations is to structure the power deposition near the coils. At low magnetic fields, the electrostatic term and the helicon term are strongly coupled. However, the propagation of the helicon component is little affected at large magnetic fields where the electrostatic term is damped.; Asymmetric antennas (m = +1,−1) produce 3-D components of the electric field lacking any significant symmetries and so must be fully resolved in 3-D. To investigate these processes, a 3-D plasma equipment model was improved to resolve 3-D components of the electric field produced by m = + 1,−1 antennas in solenoidal magnetic fields. For magnetic fields of 10–600 G, rotation of the electric field was observed downstream of the antenna where significant power deposition also occurs.