Reversal of the asymmetry in a cylindrical coaxial capacitively coupled Ar/Cl₂ plasma

Journal Article · Thu Oct 08 00:00:00 EDT 2015 · Journal of Vacuum Science and Technology A

DOI:https://doi.org/10.1116/1.4932562· OSTI ID:1245208

Upadhyay, Janardan ^[1]; Im, Do ^[1]; Popović, Svetozar ^[1]; Vušković, Leposava ^[1]; Valente-Feliciano, Anne -Marie ^[2]; Phillips, Larry ^[2]

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1. Old Dominion Univ., Norfolk, VA (United States)
2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

The reduction of the asymmetry in the plasma sheath voltages of a cylindrical coaxial capacitively coupled plasma is crucial for efficient surface modification of the inner surfaces of concave three-dimensional structures, including superconducting radio frequency cavities. One critical asymmetry effect is the negative dc self-bias, formed across the inner electrode plasma sheath due to its lower surface area compared to the outer electrode. The effect on the self-bias potential with the surface enhancement by geometric modification on the inner electrode structure is studied. The shapes of the inner electrodes are chosen as cylindrical tube, large and small pitch bellows, and disc-loaded corrugated structure (DLCS). The dc self-bias measurements for all these shapes were taken at different process parameters in Ar/Cl₂ discharge. Lastly, the reversal of the negative dc self-bias potential to become positive for a DLCS inner electrode was observed and the best etch rate is achieved due to the reduction in plasma asymmetry.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• Grant/Contract Number: AC05-06OR23177
• OSTI ID: 1245208
• Report Number(s): DOE/OR/23177--3647; JLAB-ACC--15-2206
• Journal Information: Journal of Vacuum Science and Technology A, Journal Name: Journal of Vacuum Science and Technology A Journal Issue: 6 Vol. 33; ISSN 0734-2101; ISSN JVTAD6
• Publisher: American Vacuum Society
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SRF cavity
asymmetric discharge
coaxial rf discharge
direct current power transmission
electrodes
high pressure
plasma etching
plasma sheaths