Radiant energy – Ion generation – Field ionization type
Reexamination Certificate
1999-01-30
2001-06-05
Berman, Jack (Department: 2881)
Radiant energy
Ion generation
Field ionization type
C250S427000, C315S111810, C315S111410, C315S111010, C313S360100, C313S362100
Reexamination Certificate
active
06242749
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of ion-emission technique, particularly to an ion source with uniform ion-beam current density on the surface of an object being treated. The ion-beam source of the invention is intended for etching, cleaning, activation, polishing, or thin-film coating of objects with large surface areas.
BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART
An ion source is a device that ionizes gas molecules and then focuses, accelerates, and emits them as a narrow beam. This beam is then used for various technical and technological purposes such as cleaning, activation, polishing, thin-film coating, or etching.
An example of wide-aperture type ion sources intended for treating objects with large surface area is the so-called Kaufman ion source, also known as a Kaufman ion engine or an electron-bombardment ion source described in U.S. Pat. No. 4,684,848 issued to H. R. Kaufman in 1987.
This ion source consists of a discharge chamber, in which plasma is formed, and an ion-optical system, which generates and accelerates an ion beam to an appropriate level of energy. A working medium is supplied to the discharge chamber, which contains a hot cathode that functions as a source of electrons and is used for igniting and maintaining a gas discharge. The plasma, which is formed in the discharge chamber, acts as an emitter of ions and creates, in the vicinity of the ion-optical system, an ion-emitting surface. As a result, the ion-optical system extracts ions from the aforementioned ion-emitting surface, accelerates them to a required energy level, and forms an ion beam of a required configuration. Typically, aforementioned ion sources utilize two-grid or three-grid ion-optical systems.
A disadvantage of such a device is that it does not provide a uniform ion-emitting surface, especially when the ion-emitting surface is large. Another disadvantage is that it requires the use of ion accelerating grids which contaminate the ion beam, and hence the surface of the object, as a result of sputtering of the material from the surface of the grid-like electrode. Another disadvantage of the Kaufman ion sources is that the ion beams emitted from such sources are still of insufficient intensity.
Attempts have been made to provide ion sources with ion beams of higher intensity by holding the electrons in a closed space between a cathode and an anode where the electrons could be held. For example, U.S. Pat. No. 4,122,347 issued in 1978 to Kovalsky et al. describes an ion source with a closed-loop trajectory of electrons for ion-beam etching and deposition of thin films, wherein the ions are taken from the boundaries of a plasma formed in a gas-discharge chamber with a hot cathode. The ion beam is intensified by a flow of electrons which are held in crossed electrical and magnetic fields within the accelerating space and which compensate for the positive spatial charge of the ion beam.
A disadvantage of devices of such type is that they do not allow formation of ion beams of chemically-active substances for ion beams capable of treating large surface areas. Other disadvantages of the aforementioned devices are short service life and high non-uniformity of ion beams.
Russian Patent No. 2,030,807 issued in 1995 to M. Parfenyonok, et al. describes an ion source that comprises a magnetoconductive housing used as a cathode having an ion-emitting slit, an anode arranged in the housing symmetrically with respect to the emitting slit, a magnetomotance source, a working gas supply system, and a source of electric power supply.
For better understanding the construction and principle of operation of an ion-beam source with a closed-loop ion-beam emitting slit and electrons drifting in crossed electric and magnetic fields, to which the present invention pertains, it would be expedient to describe the construction and operation of such a source in more detail.
FIGS. 1 and 2
schematically illustrate the aforementioned known ion source with a circular ion-beam emitting slit. More specifically,
FIG. 1
is a sectional side view of an ion-beam source with a circular ion-beam emitting slit, and
FIG. 2
is a sectional plan view along line II—II of FIG.
1
.
The ion source of
FIGS. 1 and 2
has a hollow cylindrical housing
40
made of a magnetoconductive material such as Armco steel (a type of mild steel), which is used as a cathode. Cathode
40
has a cylindrical side wall
42
, a closed flat bottom
44
and a flat top side
46
with a circular ion emitting slit
52
.
A working gas supply hole
53
is formed in flat bottom
44
. Flat top side
46
functions as an accelerating electrode. Placed inside the interior of hollow cylindrical housing
40
between bottom
44
and top side
46
is a magnetic system in the form of a cylindrical permanent magnet
66
with poles N and S of opposite polarity. An N-pole faces flat top side
46
and S-pole faces bottom side
44
of the ion source. The purpose of a magnetic system
66
with a closed magnetic circuit formed by parts
66
,
40
,
42
, and
44
is to induce a magnetic field in ion emitting slit
52
. It is understood that this magnetic system is shown only as an example and that it can be formed in a manner described, e.g., in aforementioned U.S. Pat. No. 4,122,347. A circular annular-shaped anode
54
, that is connected to a positive pole
56
a
of an electric power source
56
, is arranged in the interior of housing
40
around magnet
66
and concentric thereto. Anode
54
is fixed inside housing
40
by means of a ring
48
made of a non-magnetic dielectric material such as ceramic. Anode
54
has a central opening
55
in which aforementioned permanent magnet
66
is installed with a gap between the outer surface of the magnet and the inner wall of opening
55
. A negative pole
56
b
of electric power source is connected to housing
40
, which is grounded at GR.
Located above housing
40
of the ion source of
FIGS. 1 and 2
is a sealed vacuum chamber
57
which has an evacuation port
59
connected to a source of vacuum (not shown). An object OB to be treated is supported within chamber
57
above ion emitting slit
52
, e.g., by connecting it to an insulator block
61
rigidly attached to the housing of vacuum chamber
57
by a bolt
63
but so that object OB remains electrically and magnetically isolated from the housing of vacuum chamber
57
. However, object OB is electrically connected via a line
56
c
to negative pole
56
b
of power source
56
. Since the interior of housing
40
communicates with the interior of vacuum chamber
57
, all lines that electrically connect power source
56
with anode
54
and object OB should pass into the interior of housing
40
and vacuum chamber
57
via conventional commercially-produced electrical feedthrough devices which allow electrical connections with parts and mechanisms of sealed chambers without violation of their sealing conditions. In
FIG. 1
, these feedthrough devices are shown schematically and designated by reference numerals
40
a
and
57
a
. Reference numeral
57
b
designates a seal for sealing connection of vacuum chamber
57
to housing
40
.
The known ion source of the type shown in
FIGS. 1 and 2
is intended for the formation of a unilaterally directed tubular ion beam. The source of
FIGS. 1 and 2
forms a tubular ion beam IB emitted in the direction of arrow A and operates as follows.
Vacuum chamber
57
is evacuated, and a working gas is fed into the interior of housing
40
of the ion source. A magnetic field is generated by magnet
66
in the accelerating gap between anode
54
and cathode
40
, whereby electrons begin to drift in a closed path within the crossed electrical and magnetic fields. Plasma
58
is formed between anode
54
and cathode
40
. When the working gas is passed through the ionization gap, tubular ion beam IB, which is propagated in the axial direction of the ion source shown by an arrow A, is formed in the area of an ion-emitting slit
52
and in an accelerating gap
52
a
between anode
54
and cathode
40
.
Maishev Yuri
Ritter James
Shkolnik Alexander
Velikov Leonid
Berman Jack
Wells Nikita
LandOfFree
Ion-beam source with uniform distribution of ion-current... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ion-beam source with uniform distribution of ion-current..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ion-beam source with uniform distribution of ion-current... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2486080