Spatially averaged (global) model of time modulated high density argon plasmas

Abstract

The behavior of argon plasmas driven by time modulated power in ‘‘high density’’ plasma reactors is investigated using a global model. The time evolution of the electron temperature and the plasma density is calculated by solving the particle and energy balance equations. In the first stage of power application during the ‘‘on’’ time, the electron temperature rapidly increases above the steady state value. In this region, charged particles accumulate in the plasma due to the relatively higher power applied than for the continuous wave (cw) case. In the first stage of the ‘‘off’’ time, the electron temperature drops quickly, yielding a smaller particle loss (Bohm) velocity. These effects give rise to higher time-average plasma densities than for the cw plasma driven by the same average power. The highest average plasma density obtained was more than twice the density of the cw plasma for a duty ratio of 25%. Even higher plasma densities were obtained for shorter duty ratios. The possibility of controlling chemical reactions in the plasma by changing the modulation period is also shown.

An ionization region model for high-power impulse magnetron sputtering discharges

“…It has an inflection point close to current maximum where the gas depletion rate is strongest, and a minimum toward the end of the pulse when the sum of the loss terms is balanced by diffusion-refill (curve (b) in figure 6(a)). An interesting observation is that in this HiPIMS discharge the ionization losses (curve (b) in figure 6(b)) dominate over the sputter wind term (curve (d)), a new finding compared with gas rarefaction as earlier modeled in dc magnetron discharges [13] and in Monte Carlo simulations of the HiPIMS discharge [26].…”

“…The model, IRM, is constructed so that parameters for different discharge geometries, target materials, pressures, electric pulse forms, and process gases can relatively easily be implemented. It is built on earlier global models [8,13,14] but contains some new features: the introduction of a fitting parameter F PWR that is adjusted to give electric input power and current that match input experimental data, the introduction of gas rarefaction through a new density balance equation for gas atoms, and a geometric limitation to the ionization region. When the fitting parameter F PWR is determined by current matching, the model output becomes completely determined by the input experimental data.…”

“…However, geometrical effects are included indirectly in the treatment of particle fluxes across the boundaries to the target and the bulk plasma. New features in the IRM compared with the earlier related models [8,13,14] are the following.…”

“…The IRM model is based on the time-dependent global (volume-averaged) model developed by Ashida et al [13] that was later extended to model an IPVD process in an inductively coupled plasma assisted magnetron sputtering discharge by Hopwood [8], and to describe the HiPIMS process by Gudmundsson [14]. The time development is defined by a set of ordinary differential equations giving the first time derivatives of the electron energy (here, the electron temperature) and the particle densities for all the particles.…”

Emission and afterglow properties of an expanding RF plasma with nonuniform neutral gas density

“…Advantages of pulsed operation include the ability to obtain high plasma densities without excessive heat loads on the system 3 and opportunities to take advantage of the unique properties of the "afterglow" plasma that remains after the power source is switched off, such as high plasma density (n i ) with very low electron temperature (T e ) 3 and intense visible and infrared (IR) light emission. 4 In this paper, we discuss some interesting properties of the emission characteristics and afterglow evolution in a high density (peak n i ) 10 19 m À3 ) pulsed radiofrequency (RF) discharge at 100-700 mTorr.…”