Electric heating – Metal heating – By arc
Patent
1996-08-27
1998-03-10
Paschall, Mark H.
Electric heating
Metal heating
By arc
21912152, 156345, 31511151, B23K 1000
Patent
active
057264139
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to an apparatus for generating a plasma by inductive coupling of high frequency (HF) energy for the plasma-supported processing of substrates.
Plasma processes are used increasingly in the technical treatment of surfaces or layers close to a surface. It may relate to the precipitation of layers, the hardening of surfaces, to the removal of a layer, or to cleaning processes.
Different methods are available for generating a plasma, such as, for instance, electron-cyclotron-resonance or straight capacitive energy coupling. In the case at hand the plasma generation is accomplished by an inductive coupling of HF energy through an especially configured antenna. There is a survey by B. J. Hopwood of this kind of plasma generation in Plasma Sources Sci. Technol. 1 (1992), 109-116.
2. State of the Art
The problem inherent in inductive coupling is that electric potentials are created on the antenna because of its finite inductance, which lead to a capacitive (E field) component of the excitation. This capacitive component is undesirable as it leads to high plasma potentials which detrimentally affect any directed treatment of a substrate.
A further problem relates to the generation of uniform plasmas over large areas, for instance, in the treatment of flat panel displays. Scaling up existing plasma sources quickly encounters technical limitations. An arbitrarily sized area of homogenous plasma density may, however, be provided by a surface array of an arbitrary number of conventionally sized individual sources. Such apparatus have been described, for instance, in U.S. Pat. Nos. 4,713,585 or 5,133,825. Compactly structured and inherently superficial plasma sources are especially suitable as individual sources.
U.S. Pat. No. 5,122,251 discloses a device for generating plasma by inductive coupling of HF energy, comprising a cylindrical plasma generating chamber which is open at one side, a gas input conduit and an antenna which partially encloses the plasma generating chamber in a plane normal to its longitudinal axis. The device is additionally provided with means arranged around the plasma generating chamber for establishing a longitudinal magnetic field within the plasma generating chamber, as well as with a device for exciting the antenna with HF energy. The antenna is configured as an open loop with the feedlines positioned side-by-side at one side of the plasma generating chamber. The particularly simple configuration of the antenna results in a compact structure of the plasma source.
An improvement of the disclosed device consists of a side-by-side arrangement of a plurality of series-connected plasma generation chambers and associated antennae connected to a common matching circuit (match box) and fed from a single HE transmitter. This makes it possible to treat larger surfaces.
The device does, however, suffer from the disadvantage mentioned above, that is the capacitive component of the plasma excitation resulting from the inductance of the antenna detrimentally affecting a directed substrate treatment.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a compact apparatus for generating a plasma by inductive coupling of HF energy which by comparison with to existing devices, has a significantly lower capacitive plasma excitation component.
In accordance with the invention, the object is accomplished by an apparatus for generating a plasma for the plasma-supported processing of substrates, having a plurality of plasma generating chambers of substantially cylindrical configuration arranged in side by side relationship, an annular antenna surrounding each chamber in a plane disposed normal to the longitudinal axis of the chamber for inductively coupling high frequency energy into each chamber, a device for establishing a longitudinal magnetic field in each of said chambers, and high frequency feed lines respectively connected to diagonally opposite points of said antenna and a source of high frequency. Speci
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Hopwood, B.J., in Plasma Sources Sci. Technol. 1 (1992) 109-116.
Baenziger Ulrich
Neumann Gerold
Scheer Hella-C.
Fraunhofer-Gesellschaft fur die angewandte . . .
Hormann Karl
Paschall Mark H.
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