Discharge model and plasma characteristics of high-power pulsed magnetron sputtering titanium target

Abstract

<sec>High-power pulsed magnetron sputtering has become a popular research tool in surface technology industry because it can prepare the films with excellent surface quality. The plasma density and metal ionization rate are the key factors affecting the quality of the film deposited by high-power pulsed magnetron sputtering. The parameters of high-power pulsed magnetron sputtering (such as applied voltage, pulse width, deposition pressure and peak current) affect the plasma density and metal ionization rate. In this paper, in order to more easily understand the plasma densities and metal ionization rates at the different process parameters, the plasma densities and ionization rates are calculated numerically. An equivalent circuit model established by MATLAB/Simulink software is used to obtain the discharge current curve of high-power pulsed magnetron sputtering titanium (Ti) target. The plasma density near the plasma sheath is calculated by the sheath resistance in the equivalent circuit model. The ionization rate of Ti is calculated by using the semi-cylinder global model theory combined with the discharge current simulated by equivalent circuit model. It is found that under the different high power pulse sputtering voltages, pulse widths and different deposition pressures, the discharge modes are of gas discharge and metal ion discharge, and the gas discharge interacts with metal ion discharge. The equivalent circuit model is produced by the main discharge mode, and the equivalent circuit model composed of capacitor, inductor and resistors in series and in parallel can be used to simulate the discharge current of Ti target. The result shows that the simulated discharge current is accurate in the rising edge and peak value in comparison with experimental data. The value of electron component in the model is related to the saturation ion current.</sec><sec>According to the sheath resistance in the model, the average plasma density in the vacuum chamber increases with increasing sputtering voltage, pulse width and deposition pressure. And the plasma density in the vacuum chamber lies in a range of (2–9) × 10¹⁷ m^–3. The particle equilibrium equation is established by using the semi-cylinder global model theory. The electron temperature (5 eV) and discharge current are used as boundary conditions to calculate the ionization rate of Ti. The value of the ionization rate of Ti is in a range of 31%–38% at different deposition pressures, and the ionization rate of Ti increases with the increase of deposition pressure.</sec>