Large volume, high density rf inductively coupled plasma

Boswell, Roderick; Porteous, R. K.

doi:10.1063/1.98257

Cited by 115 publications

(48 citation statements)

References 3 publications

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“…5 Neutral depletion was also postulated to occur in helicon sources although again no measurements of the phenomena were reported. 6 More recently a number of hydrodynamic, Monte-Carlo, or hybrid simulations of plasma and neutral transport in high density reactors have been reported [7][8][9] and have been used to predict neutral depletion within largesized HDP sources. A few experimental observations of neutral depletion within HDP sources have also been reported.…”

Section: Previous Neutral Depletion Studiesmentioning

confidence: 99%

Neutral depletion and transport mechanisms in large-area high density plasma sources

Tynan

1999

Journal of Applied Physics

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Plasma uniformity has been recognized as a significant parameter in large-sized high density plasma processing tools, but neutral uniformity issues have received less attention. In this article we show experimental and modeling results which indicate that significant neutral uniformity variations can occur in high density plasma processing tools. The experiments are carried out in both inductively coupled plasma and helicon plasma sources. A movable static pressure gauge is used to obtain the static radial neutral pressure distribution both with and without a discharge present. Without a wafer present in the reactor, significant (∼20%–40%) reductions in neutral pressure are observed in these sources during steady-state plasma operations. This spatially averaged neutral depletion is accompanied by hollow neutral pressure profiles. The degree of on-axis neutral depletion depends upon both plasma density and neutral fill pressure. We show that the “plasma pumping” effect, wherein electron impact ionization of neutral particles is followed by their rapid removal from the plasma by the pre-sheath electric field, can reproduce the experimental results. This effect has the potential to result in large (∼50%) neutral density variation across 300 mm wafers in high density plasma sources.

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Section: Previous Neutral Depletion Studiesmentioning

confidence: 99%

Neutral depletion and transport mechanisms in large-area high density plasma sources

Tynan

1999

Journal of Applied Physics

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“…3 In fact, Boswell and Porteous postulated that fully ionized plasmas in the center of helicon discharges were required for pressure balance between the hot plasma in the center and the dense, cold neutrals at the plasma edge. 4 However, experimental confirmation of hollow neutral density profiles in helicon sources has been limited. 5 The phenomenon of neutral pumping, whereby neutral atoms are ionized and then the ions are accelerated by the presheath electric field towards the chamber wall where they recombine and are pumped away, has also been investigated by several groups.…”

Section: Introductionmentioning

confidence: 99%

Neutral argon density profile determination by comparison of spectroscopic measurements and a collisional-radiative model (invited)

Keesee

Scime

2006

Review of Scientific Instruments

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Neutral atoms play important roles in non-fully-ionized plasmas. In helicon sources, neutral pumping and neutral damping of waves are poorly understood. Measurement of the spatial distribution of neutral atoms is possible with spectroscopic diagnostics such as laser-induced fluorescence ͑LIF͒ and passive emission spectroscopy. However, these measurements typically apply to an excited neutral atom state, rather than the entire neutral population. With a collisional-radiative ͑CR͒ model employing Langmuir probe measured electron parameters in argon helicon source plasmas, we have reproduced LIF and emission spectroscopy measured radial profiles for three excited neutral states. The CR model indicates a neutral depletion on axis of at least 60%. Simple calculations based on measured edge neutral pressures and peak plasma densities significantly underestimate the degree of ionization in the core of the helicon plasma.

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“…The large plasma diffusion system used in Canberra, WOMBAT, 15 has been described elsewhere but it briefly consists of a glass source tube 50 cm long and 18 cm in diameter attached on axis to a large stainless steel diffusion chamber 200 cm long and 90 cm inner diameter, as shown in Fig. 2.…”

Section: B Australian National Universitymentioning

confidence: 99%

Spatially limited ion acoustic wave activity in low-pressure helicon discharges

et al. 2004

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Ion acoustic wave phenomena are studied and compared in two low-pressure argon discharges created by helicon sources. The wave amplitudes are spatially localized near the edge of a plasma column as the amplitudes of the "mirror waves" that are separated from the helicon source frequency by the ion wave frequency. Dependencies of the ion wave on radial position, pressure, input power, and magnetic field are investigated. Measurements of the wavelength show that the wave is traveling azimuthally at approximately the ion sound speed in the direction of electron gyration. Although the wave spectra are indicative of a parametric decay phenomenon, it seems more likely that the radial plasma pressure gradient drives an ion acoustic instability which then modulates the helicon source.

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Large volume, high density rf inductively coupled plasma

Abstract: Magnetized argon plasma columns with peak densities of greater than 1018 m−3, lengths of 2 m, and full width half-maximum diameters of 0.3 m have been created at pressures of 40 mPa (3×10−4 Torr) with input powers of 1.5 kW of 7 MHz rf.

Cited by 115 publications

References 3 publications

Neutral depletion and transport mechanisms in large-area high density plasma sources

Neutral depletion and transport mechanisms in large-area high density plasma sources

Neutral argon density profile determination by comparison of spectroscopic measurements and a collisional-radiative model (invited)

Spatially limited ion acoustic wave activity in low-pressure helicon discharges

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