Coating apparatus – Gas or vapor deposition – With treating means
Patent
1996-09-05
1999-05-04
Dang, Thi
Coating apparatus
Gas or vapor deposition
With treating means
20429841, C23C 1400
Patent
active
059000635
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for coating a substrate, and in particular, to a method and apparatus which creates a magnetoplasma in the vicinity of an evaporated source material to assist the transport of an evaporant and/or ions of a background gas under the influence of an applied magnetic field for deposition on a substrate material.
DESCRIPTION OF THE PRIOR ART
The transporting of plasma by means of a magnetic field is well known in the literature, and is commonly used for forming thin film coatings in the case where the source of material is a cathodic arc (Aksenov et al, Soviet Journal of Plasma Physics 4 (1978), page 425).
The transportation of plasma by magnetic fields has also been described, in U.S. Pat. No. 4,810,935, entitled `Method and apparatus for producing large volume magnetoplasmas` by R W Boswell. In this case no source of evaporation was discussed, but rather the plasma was created in gases admitted to the process.
The use of a thermal evaporation source with a plasma in its vicinity is also well known as the `ion plating` process. That known process differs from the present invention by its use of electric fields only to transport the plasma to the substrate rather, than a magnetic field and an electric field, as in the invention.
The use of energetic ions to densify a film is also well known as Ion Assisted Deposition. That known process differs from the present invention by its use of a source of bombarding ions (plasma or ion source) not transported by a magnetic field and separate from the source of deposited material.
SUMMARY OF THE INVENTION
The present invention seeks to provide a method and apparatus for forming a coating on a substrate, which differs from those prior art methods and apparatus hereinbefore discussed.
The present invention also seeks to provide a method and apparatus for forming a coating on a substrate which has a wide variety of applications therefor, such as producing "doped" films or alloys of various materials, for example, semiconductor materials.
In one broad form, the present invention provides an apparatus for forming a coating on a substrate, comprising: the said evaporant and (most usually) also from a background gas; and, transport said magnetoplasma to said substrate.
Preferably, said plasma generation chamber is supplied intermediate said evaporator and said substrate.
Preferably, the antenna is excited with radio frequency power, which is preferably in the frequency range 10 to 30 MHz.
Also preferably, each of said evaporator, said plasma generation chamber and said substrate are substantially axially concentric.
Most preferably, said plasma generation chamber is situated above said evaporator and below said substrate in a substantially vertical configuration.
In the preferred embodiment, said magnetic field acts to increase the density of said magnetoplasma and to increase the ionisation proportion of said evaporant and any background gases admitted to the chamber.
In another preferred embodiment the ionisation proportion of said evaporant is low or zero, and in the primary effect of the magnetic field is to transport ions of the said background gas to the surface to carry out the process of ion assisted deposition.
In another preferred embodiment the background gas contains precursors enabling the deposition of a doped film onto said substrate which originates from the background gas, while the dopant originates from the evaporant.
Most preferably, said evaporator is comprised of a crucible possibly having more than one compartment therein, each compartment housing a different source material, and whereby said evaporator is controlled to produce evaporant(s) from each source material, as desired.
In a preferred form, a bias voltage (DC or RF) is applied to said substrate.
Perhaps most preferably, said bias voltage is up to about 4 kV.
Preferably said substrate is heated or cooled.
In a most preferred form, a potential maximum in the plasma is located near to the evaporator such that said
REFERENCES:
patent: 4683838 (1987-08-01), Kimura et al.
patent: 4990229 (1991-02-01), Campbell et al.
patent: 5126030 (1992-06-01), Tamagaki et al.
Boswell Roderick
Durandet Antoine
MacKenzie David
Chambers Guy W.
Dang Thi
The Australian National University
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