Djilali Benyoucef

Ar+/Ar, O2+/O2 and N2+/N2 Elastic Momentum Collision Cross Sections: Calculation and Validation Using the Semi-Classical Model

The aim of this paper is to obtain relevant sets of collision cross sections of the parent ions in low pressure discharges in argon, oxygen, and nitrogen, i.e., Ar+ in Ar, O2+ in O2 and N2+ in N2. These ion data are first discussed and then validated from comparisons between the calculated transport coefficients and those measured in the literature. The elastic momentum transfer collision cross sections are determined from a semi-classical approximation for the phase shift calculation based on a 12-6-4 inter-particle potential while ion transport coefficients are determined versus the reduced electric field from Monte Carlo simulations.

Self-consistent particle modeling of radio frequency discharge in Ar/O2 mixtures: Effects of crossed electric and magnetic fields and partial pressure

A particle-in-cell/Monte Carlo model is developed to study and analyze the electrical characteristics of the nonequilibrium plasma created by radio frequency (RF) discharge in Ar/O2 mixtures in the presence of crossed electric and magnetic fields. The method of collision treatment is based on an optimized estimation of the free time flight. The needed basic data—more specifically, the ion–neutral cross sections—are determined first. The simulation conditions are 50 mTorr for the total gas pressure and 200 V for the peak of the RF voltage at a frequency of 13.56 MHz. The magnetic field is varied from 0 to 50 G. The effect of the partial pressure ratio of O2 in the mixture and the effect of the magnitude of the magnetic field are discussed. In particular, the results show an increase of the plasma density that is ten times higher in the presence of a magnetic field.

PIC MC Using Free Path for the Simulation of Low-Pressure RF Discharge in Argon

In this paper, we used the particle-in-cell/Monte Carlo techniques 1 Dimension 3 Velocities and 3 Dimensions 3 Velocities to simulate low-pressure radio-frequency (RF) discharge in argon. The plasma conditions are 50-100 mtorr of pressure and 200 V of peak RF voltage at 13.56 MHz. The method used in collision treatment is based on an optimized estimation of the collision free path which is independent of the electron energy. It depends only on the maximum of total cross sections. To reduce the number of null collisions, two maximums of total cross sections are chosen. The results obtained were compared with data from experiments that were already carried out.

Particle modelling of magnetically confined oxygen plasma in low pressure radio frequency discharge

The main objective of this paper is the modelling and simulation of a radio frequency (RF) discharge in oxygen at low pressure and at room temperature, including the effect of crossed electric and magnetic fields for generation and confinement of oxygen plasma. The particle model takes into account one axial dimension along the electric field axis and three velocity components during the Monte Carlo treatment of the collisions between charged particles and background gas. The simulation by this developed code allows us not only to determine the electrodynamics characteristics of the RF discharge, but also to obtain kinetics and energetic description of reactive oxygen plasma at low pressure. These information are very important for the control of the deep reactive-ion etching technology of the silicon to manufacture capacitors with high density and for the deposition thick insulating films or thick metal to manufacture micro-coils. The simulation conditions are as follows: RF peak voltage of 200 V, freque...

Effects of Increasing Magnetic Field and Decreasing Pressure on Asymmetric Magnetron Radio Frequency

The aim of this paper is to define the optimal couple of the total pressure and the magnetization of the permanent magnets for self-maintaining under optimal conditions an asymmetric magnetron radio frequency (RF) discharge. Electro-dynamics discharge simulations are based on a self-consistent particle model using Monte Carlo method for the treatment of collisions between charged particle and background gas. The simulations are performed at a fixed mixture of 90% Ar/10% O2 by simultaneously decreasing the total pressure P and increasing the magnetization σ. In the case of a sinusoidal RF power supply with 200 V for peak voltage and 13.56 MHz for frequency, the magnetization of the permanent magnets varies between 500 Gauss at 25 mTorr to 1400 Gauss at 5 mTorr. We use a semianalytical method for calculating the applied magnetic field generated by two permanent magnets that are composed of concentric rings. This enables generating, in a specific region of the interelectrode gap near the cathode, an optimal magnetic field crossing the RF electric field for application to magnetron discharges. The simulation results of RF magnetron discharge shown that, in the case of the lowest considered pressure (5 mTorr), a high magnetization of 1400 Gauss is the most favorable for self-maintaining the discharge and generating a quasi-ion beam energy distribution near the cathode that is interesting for cathode sputtering processes.

{\rm Ar}/{\rm O}_{2}

In this paper, we present a contribution to the electrical modeling of positive dc point-to-plane corona discharges in dry air (20%O2 and 80%N2) at atmospheric pressure. The electrical equivalent circuit of the proposed model is regarded as a variable resistor in series with a variable capacitor. The evolutions of the electrical parameters are obtained using a mathematical method of identification based on the recursive least squares algorithm. For the same experimental conditions, the comparison between the measured discharge current and the calculated currents obtained using the identified electrical parameters of the proposed equivalent model shows good agreement, which validates the model as well as the method of identification. To validate this work, results and discussions are given in two different operating points.

Discharges

In this paper, we present an analytical method for calculating the axial and radial components of the magnetic field created by a permanent magnet in the form of a ring used in a magnetron radio frequency (RF) reactor. The calculation is based on the symmetric integral of the first kind; it was performed under a Linux 64-bit operating system. This analytical method allows us to accurately assess the magnetic field, and it allows us to reduce the computational time. Finally, in order to validate the results, they are successfully compared with the results obtained by a numerical method based on finite-difference method.

Modeling and Identification of Electrical Parameters of Positive DC Point-to-Plane Corona Discharge in Dry Air Using RLS Method

This paper proposes the design of a new adaptive power control scheme for full bridge series-parallel resonant inverter with AVC control strategy. This scheme is used to control the heating process by adjusting the output power of the inverter irrespective of load and line variations. Two independent control loops are used in this technique: power control loop and frequency control loop (PLL). In the first, an adaptive PID controller with parallel structure is used to force the output power to track the desired trajectory. The adaptive PI controller of the PLL varies the DC input of the VCO in order to generate the required output frequency to maintain ZVS operating during the heating process. The desired performances of the closed loop control are given by two independent reference models. The design of the adaptive mechanism is based on MIT rule and the small signal model of the inverter around the operating point. Compared with other works, the adaptive mechanism redesigns the parameter gains of the PID and the PI controllers in order to avoid the disturbance. Simulation results confirm the effectiveness of the proposed system.