Control of plasma uniformity in a capacitive discharge using two very high frequency power sources

Journal Article · Sat Aug 01 00:00:00 EDT 2009 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3183946· OSTI ID:21359342

Bera, Kallol; Rauf, Shahid; Ramaswamy, Kartik; Collins, Ken ^[1]

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1. Applied Materials, Inc., 974 E. Arques Ave., M/S 81517, Sunnyvale, California 94085 (United States)

Very high frequency (VHF) capacitively coupled plasma (CCP) discharges are being employed for dielectric etching due to VHF's various benefits including low plasma potential, high electron density, and controllable dissociation. If the plasma is generated using multiple VHF sources, one can expect that the interaction between the sources can be important in determining the plasma characteristics. The effects of VHF mixing on plasma characteristics, especially its spatial profile, are investigated using both computational modeling and diagnostic experiments. The two-dimensional plasma model includes the full set of Maxwell equations in their potential formulation. The plasma simulation results show that electron density peaks at the center of the chamber at 180 MHz due to the standing electromagnetic wave. Electrostatic effects at the electrode edges tend to get stronger at lower VHFs such as 60 MHz. When the two rf sources are used simultaneously and power at 60 MHz is gradually increased, the ion flux becomes uniform and then transitions to peak at electrode edge. These results are corroborated by Langmuir probe measurements of ion saturation current. VHF mixing is therefore an effective method for dynamically controlling plasma uniformity. The plasma is stronger and more confined when the 60 MHz source is connected to the smaller bottom electrode compared to the top electrode.

• OSTI ID: 21359342
• Journal Information: Journal of Applied Physics, Vol. 106, Issue 3; Other Information: DOI: 10.1063/1.3183946; (c) 2009 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BOUNDARY LAYERS
DIELECTRIC MATERIALS
DISSOCIATION
ELECTRODES
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
HIGH-FREQUENCY DISCHARGES
LANGMUIR PROBE
MAXWELL EQUATIONS
MHZ RANGE 100-1000
PLASMA
PLASMA DENSITY
PLASMA POTENTIAL
PLASMA SIMULATION
PLASMA WAVES
TWO-DIMENSIONAL CALCULATIONS
DIFFERENTIAL EQUATIONS
ELECTRIC DISCHARGES
ELECTRIC POTENTIAL
ELECTRIC PROBES
EQUATIONS
FREQUENCY RANGE
LAYERS
MATERIALS
MHZ RANGE
PARTIAL DIFFERENTIAL EQUATIONS
PROBES
RADIATIONS
SIMULATION