Sharma, S and Sirse, N and Kuley, A and Sen, A and Turner, MM (2020) Driving frequency effect on discharge parameters and higher harmonic generation in capacitive discharges at constant power densities. In: Journal of Physics D: Applied Physics, 54 (5).

PDF
Jou_Phy_DAp_545_2020.pdf  Published Version Download (3MB)  Preview 
Abstract
Very high frequency (VHF) driven capacitive discharges are now being increasingly adopted for plasmabased materials processing due to their high processing rates and lower substrate damage. Past studies related to complex plasma dynamics and higher harmonics generation in such systems were limited to constant voltage/current conditions, whereas, industrial systems are mostly driven by constant power density sources. In the present study, using particleincell (PIC) simulation, we explore the dynamics of collisionless symmetric capacitive discharges that is operated at constant power densities. Our focus is on the effect of the driving frequency on the discharge parameters like the electron density/temperature, the electron energy distribution function (EEDF), the ion energy distribution function (IEDF), and the generation of higher harmonics in the device. The simulations are performed for a driving frequency from 27.12 to 100 MHz in argon plasma at a gas pressure of 1 Pa and for two values of the power density, namely, 2 kW m3 and 20 kW m3. It is observed that the required discharge voltage for maintaining constant power density decreases and discharge current increases with an increase in the driving frequency. A transition frequency is observed at both power densities. The density decreases (electron temperature increases) before the transition frequency and the trend is reversed after crossing the transition frequency. The EEDF shows an enhancement in the population of the midenergy range of electrons as the driving frequency increases up to the transition frequency thereby changing the shape of EEDF from biMaxwellian to nearly Maxwellian, and then transforms into a nearly biMaxwellian at higher driving frequencies. The IEDF at the electrode surface shows bimodal behaviour at a lower driving frequency, becoming more pronounced at a power density of 20 kW m3, and then turning into a single energy peak. The corresponding maximum ion energy is found to decrease with driving frequency.
Item Type:  Journal Article 

Publication:  Journal of Physics D: Applied Physics 
Publisher:  IOP Publishing Ltd 
Additional Information:  The copyright for this article belongs to the Authors. 
Keywords:  Distribution functions; Dynamics; Electron energy analyzers; Electron energy levels; Electron temperature; Electrons; Harmonic analysis; Harmonic generation; Plasma diagnostics; Plasma simulation, Capacitive discharges; Constant power density; Electron energy distribution functions; High processing rates; Higher harmonics generation; Ion energy distribution functions; Particleincell simulations; Transition frequencies, Electric discharges 
Department/Centre:  Division of Physical & Mathematical Sciences > Physics 
Date Deposited:  23 Jan 2023 10:19 
Last Modified:  23 Jan 2023 10:19 
URI:  https://eprints.iisc.ac.in/id/eprint/79268 
Actions (login required)
View Item 