Note: Descriptions are shown in the official language in which they were submitted.
CA 02210130 2003-06-26
DEVICE FOR TREATING PLANAR ELEMENTS WITH A PLASMA JET
BACKGROUND OF THE INVENTION
Field of the Invention.
The present invention relates to the field of plasma technology and may be
used
in electronics and electrical engineering when treating planar elements, for
example,
semiconductor wafers, substrates, printed circuit boards, compact disks and
other
products.
Description of the Related Art.
There has long been known a device for studying a plasma-surface interaction,
a device that comprises a plasma generator, a power source therefor, a system
for the
plasma generator displacement, a system for displacing samples, a gas
distribution
system and a control system (see, Theses of the Reports at the 10th All-Union
Conference, P.P. Kulik et al., "Low-Temperature Plasma Generators," Part II,
Minsk,
ITMS Publishers, Academy of Sciences of Byelorussian Soviet Socialist
Republic,
1986, p. 135). However, this device has a number of disadvantages.
The absence of a quick-operating loading-unloading system results in a large
expenditure of time and, hence, plasma generator energy that is consumed to no
purpose when plates-samples to be treated are replaced. The inability to
simultaneously treat several plates-samples one right after another decreases
the output
of the device.
The fact that there are present in this device a number of control and
measuring
means that inhibit any repeated treatment of samples according to a rigidly
prescribed
cycle, unambiguously defines this device as one purely for research.
Taken together, the above-mentioned features result in the fact that the
device
cannot be used under conditions of series production.
The closest prior art has been described in International Application No. WO
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92/21220, H05H 1/40, 1992, which discloses a device for treating wafers with a
plasma
jet, comprising a plasma jet generator; gas supplying means; a set of holders
for wafers
to be treated, said holders being structurally made in the form of a turntable
having a
drive for effecting angular displacement thereof and for facing a generator
plasma jet
turned downwards; each of the holders being made in the form of a horizontal
platform
mounted for rotation about the axis passing through the center thereof and
being
perpendicular to the plane of said platform; and said plasma jet and wafer
holder
having the possibility of being displaced with respect to each other in the
direction of
at least one axis of coordinates and may be in or out of contact with each
other.
The main drawbacks associated with this device include an underproductivity
created by the large number of manual operations necessary when loading-
unloading
the wafers to be treated. In addition, the wafers treated are inferior in
quality due to the
possibility of surface damage when contact-attaching in the holder.
Moreover, the direction of the plasma jet from top to bottom necessitates
taking
the measure of the cooling of the plasma generator from overheating caused by
upwardly moving hot gases formed during operation of the plasma generator.
SUMMARY OF THE INVENTION
The application according to the present invention provides a device for
treating
wafers with a plasma jet, comprising a plasma jet generator, gas supplying
means and a
set of holders for wafers to be treated. The holders have a drive for
effecting angular
displacement of the wafers and face a generator plasma jet. Each of the
holders is made
in the form of a horizontal platform to rotate about the axis passing through
the
geometric center thereof and perpendicular to a plane of said platform. Said
plasma jet
and wafer holder can be displaced with respect to each other in the direction
of at least
one axis of coordinates, and they may be in or out of contact with each other.
The device
further comprises a manipulator, storage devices for the wafers to be treated,
and a
closed chamber having a gas exchange system with the wafer holders and a
plasma jet
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generator located inside said chamber in such a way that a plasma jet is
directed from
bottom upwards in respect of a plane of locating horizontal platforms of said
wafer
holders. The closed chamber is provided with a window in which a movable
shutter is
installed. The manipulator is located in such away that it contacts said
storage devices
directly and with said wafer holder indirectly, through the chamber window.
Each of the
wafer holders is provided with a limiter at the edges and has its horizontal
platform
provided with at least three vortex chambers and three tangential channels
perpendicular
to a plane of said horizontal platform. Each of these vortex chambers is
provided with an
open portion located on a level end surface of the wafer holder, coupled
through a
tangential channel to the gas supplying means and located in such a way that
the vortex
flows that are formed make possible the positioning of the platform near the
holder and
the cooling of its individual areas to equalize, over the wafer surface, the
amount of
energy used for treatment thereof. The limiters on the wafer holder platforms
are
fabricated so that the rods are mounted at an angle a> 90 to the plane of
said
horizontal platform of the wafer holder. In so doing, their length, 1, is
chosen such that
21 sin (a > 90 ) > A,
where A denotes a maximum deviation from axisymmetric arrangement of the
treated
wafers in said storage devices.
The proposed device in accordance with the present invention achieves its
technical results because it contains the following features:
(1) It provides the device with a common rotary drive for the holders, with
this
drive mounted inside the closed chamber and having its actuating mechanism
connected to each of the holders. This drive greatly enhances the output of
the device.
(2) It introduces a manipulator, with storage devices for the wafers, to be
treated, which makes it possible to further enhance the treatment capacity
while
reducing the time needed for loading-unloading the wafers.
(3) It further introduces a wafer holder with at least three vortex chambers
and
three tangential channels with the axes of said vortex chambers perpendicular
to the
horizontal platform of the holder, where each of said vortex chambers being
coupled to
the tangential channel connected to the gas supplying means. This permits the
stable
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positioning of the wafer to be treated in the vicinity of the holder with a
gas gap
without touching the wafer and the holder, which, in turn, makes it possible
to upgrade
treatment quality due to the absence of the touch traces (scratches).
(4) It arranges each of the vortex. chambers in the holder such that vortex
flows
formed by said vortex chambers make possible the fulfillment, at each side the
wafer
surface, of the condition
Qo = QI+Q2,
where:
Qo = a constant - an amount of energy for heating the wafer in the given site;
Ql - an amount of energy received by the given site of the wafer surface with
due regard to thermal transparency thereof;
Q2 - an amount of energy available at the expense of interaction with a
material
of the wafer surface in the given site.
This makes it possible to produce more uniform, and hence, higher-quality
treatment of
the wafer. This result is based on fact that each vortex chamber, when
creating a gas
vortex, permits not only the positioning of the wafer near the holder but also
the
cooling of individual areas of the wafer to be treated. Since in the process
for
treatment, different sites on the surface of the wafer to be treated are
originally under
different thermal conditions, then the energy balance caused by these vortex
flows
make possible the establishment of conditions that equalize Qo at all sites of
the wafer.
(4) It uses limiters on the holders in the rods mounted at an angle a> 90 to
the
horizontal platform of the holder, with their length 1 being chosen such that
21 sin (a > 90 ) > A,
where A denotes a maximum deviation from axisymmetric arrangement of the
wafers
in said storage devices, creates the possibility of the accuracy needed when
loading-
unloading the wafers, without using additional centering means.
Therefore, in accordance with the present invention, there is provided a
device
for treating wafers with a plasma jet, comprising a plasma jet generator; gas
supplying
means; a set of holders for wafers to be treated, said holders having a drive
for effecting
angular displacement thereof and for facing a generator plasma jet; each of
the holders being
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made in the form of a horizontal platform mounted for rotation about an axis
passing through
a geometric center thereof and perpendicular to a plane of said platform; said
plasma jet and
wafer holders being displaced with respect to each other and may be in or out
of contact with
each other, said plasma jet generator being located such that a plasma jet is
directed
upwardly in respect of a plane of said horizontal platforms of said wafer
holders; and
cooling means associated with each horizontal platform in fluid flow
communication with
said gas supplying means and located such that resulting gas flows permit the
positioning
of the platform near a holder and improve cooling of individual areas over the
wafer
surfaces while avoiding the need to provide additional cooling of said plasma
generator
due to natural convection of the hot gases.
Also in accordance with the present invention, there is provided a device for
treating wafers with a plasma jet, comprising a plasma jet generator, gas
supplying
means; a set of holders for wafers to be treated, said holders having a drive
for
effecting angular displacement thereof and for facing a generator plasma jet;
each of
the holders being made in the form of a horizontal platform mounted for
rotation about
an axis passing through a geometric center thereof and perpendicular to a
plane of said
platform; said plasma jet and wafer holders being displaced with respect to
each other
and may be in or out of contact with each other; a plasma jet generator
located such
that a plasma jet is directed in the direction of said horizontal platforms of
said wafer
holders, each wafer holder being provided with at least three vortex chambers
and three
tangential channels in fluid flow communication between said gas supplying
means
and said chambers, said chambers defining axes substantially perpendicular to
a plane
of said horizontal platforms; each of said vortex chambers being provided with
an open
portion located on a level end surface of the wafer holder, coupled through
the
tangential channel to said gas supplying means and located such that resulting
vortex
flows formed permit the positioning of each wafer near the holder and cooling
of its
individual areas to equalize, over each wafer surface, an amount of energy
used for
treating the wafer surfaces.
Still in accordance with the present invention, there is provided a device for
treating wafers with a plasma jet, comprising a plasma jet generator; gas
supplying
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means; a set of holders for wafers to be treated, each having an edge, said
holders
having a drive for effecting angular displacement thereof and for facing a
generator
plasma jet; each of the holders being made in the form of a horizontal
platform
mounted for rotation about an axis passing through a geometric center thereof
and
being perpendicular to a plane of said platform; said plasma jet and wafer
holders
being displaced with respect to each other and may be in or out of contact
with each
other, a plasma jet generator located such that a plasma jet is directed in
the direction
of said horizontal platforms of said wafer holders, each of the wafer holders
being
provided with a limiter at the edges and cooling means associated with each
horizontal
platform in fluid flow communication with said gas supplying means and located
such
that resulting gas flows permit the positioning of each wafer near a holder
and cooling
of its individual areas, said limiters on the wafer holder platforms having
lengths and
being arranged to limit maximum deviation from axisymmetric arrangement of the
treated wafers during treatments thereof.
Still further in accordance with the present invention, there is provided a
device
for treating wafers with a plasma jet, comprising a plasma jet generator; gas
supplying
means; a set of holders for wafers to be treated, said holders having a drive
for effecting
angular displacement thereof and for facing a generator plasma jet; each of
the holders
being made in the form of a horizontal platform mounted for rotation about an
axis
passing through a geometric center thereof and perpendicular to a plane of
said platform;
said plasma jet and wafer holders being displaced with respect to each other
and may be
in or out of contact with each other, said plasma jet generator being located
such that a
plasma jet is directed upwardly in respect of a plane of said horizontal
platforms of said
wafer holders; cooling means associated with each horizontal platform in fluid
flow
communication with said gas supplying means and located such that resulting
gas flows
permit the positioning of the platform near a holder and improve cooling of
individual
areas over the wafer surfaces while avoiding the need to provide additional
cooling of
said plasma generator due to natural convection of the hot gases; a
manipulator; storage
devices for the wafers to be treated; and a closed chamber having a gas
exchange system
with the wafer holders and a plasma jet generator located inside said chamber.
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Still further in accordance with the present invention, there is provided a
device for treating wafers with a plasma jet, the said device comprising: a
plasma jet
generator; gas supplying means; a set of holders for wafers to be treated, the
said
holders having a drive for effecting angular displacement thereof and for
facing a
generator plasma jet, each of the holders being made in the form of a
horizontal
platform mounted for rotation about an axis passing through a geometric center
thereof and perpendicular to a plane of the said platform, the said plasma jet
and
wafer holders being displaceable with respect to each other and in or out of
contact
with each other; said plasma jet generator is located such that a plasma jet
can be
directed upwardly in respect of a plane of the said horizontal platforms of
the said
wafer holders; and in that cooling means is associated with each horizontal
platform,
the said cooling means being in fluid flow communication with the said gas
supplying
means, defining an axis substantially perpendicular to a plane of the said
horizontal
platforms, being provided with an open portion located on a level end surface
of the
wafer holder and being located such that gas vortex flows that are formed
permit the
positioning of the wafer near a holder and improve cooling of individual areas
over
the wafer surfaces while avoiding the need to provide additional cooling of
the said
plasma generator due to natural convention of the hot gases.
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BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent from the
following description, when taken in connection with the accompanying
drawings, in
which:
FIG. 1 is a view showing a device for treating wafers with a plasma jet;
FIG. 2 is a "breakaway" top plan view of FIG. 1;
FIG. 3 is a functional diagram of an actuating mechanism of a conunon rotary
drive for holders;
FIG. 4 is a view showing a wafer holder; and
FIG. 5 is a sectional view along line 5-5 of FIG. 4.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIGS. 1, 2 illustrate a device for treating wafers with a plasma jet,
comprising a
closed chamber 1; a gas exchange system 2; a power supply unit 3; gas
supplying means
4; and a control system 5. The closed chamber 1 is provided with a window 6 in
which a
movable shutter 7 with a drive 8 is installed. Inside the closed chamber 1, on
a base 9, a
generator 10 of a plasma jet 11 and an angular displacement drive 12 with its
upright
shaft 13 coupled to holders 14 are located. The generator 10 of the plasma jet
11 facing
the holders 14 is mounted on the base 9 on a support 15 adjustable for height
such that
the axis of the plasma jet 11 and respective axes of each of the holders 14
are equidistant
from the axis of the upright shaft 13 of the angular displacement drive 12.
Referring to
FIG. 4, the holders 14 are made in the form of horizontal platforms 16 with
limiters 17.
Said limiters 17 are fabricated as the rods, for example, cylindrical rods.
With reference
to FIG. 3, horizontal platforms 16 are set in rotation about their axes by a
drive 18, for
example, by means of an actuating mechanism 19 through a step-by-step
interaction of
its gears 20, 21, 22 and pulleys 23, 24. In FIGS. 4 and 5 the horizontal
platforms 16 are
provided with vortex chambers 25 each having an open portion located on a
level end
surface of the holder 14 and coupled to a tangential channel 26 connected to
said gas
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supplying means 4. In FIG. 1, outside the closed chamber 1, on the base 9, a
manipulator
27 and storage devices 28 for wafers 29 are mounted.
The device operates as follows.
In the initial state, one of the storage devices 28 is provided with wafers
29, while
the other is free from the wafers. The manipulator 27 grips a bottom wafer 29
in the
storage device 28 and transports it through a window 6 (with a shutter 7
opened by a
drive 8) into the closed chamber 1. At this moment, the first of the holders
14 is being
loaded. The manipulator 27 conveys the wafer 29 into a position below the
horizontal
platform 16 of the first holder 14.
By switching on the gas supplying means 4 in the vortex chamber 25 and the
channel 26, of the holder 14, gas vortex flows are generated for the
positioning /
maintaining of the wafer 29 at a distance of about 0.5 - 1.0 mm from the level
end
surface of the platform 16 of the holder 14. At that moment, the manipulator
14
releases the wafer 29. The wafer is now loaded. Thereupon, the next wafer is
loaded.
In the embodiment illustrated here, a device for treating wafers with a plasma
jet is provided with five wafer holders angularly displaced at an angle of 72
to one
another in the horizontal plane. Feeding the next holder in the loading zone
is
performed with an angular displacement drive 12 for the holder 14.
Once all the holders are loaded, the manipulator 27 is withdrawn from the
closed chamber 1 while closing the shutter 7 with the drive 8. The required
gas is then
supplied to the chamber. By means of the support 15, the generator 10 of the
plasma jet
11 is mounted, with respect to the surface of the wafer 29 to be treated, at a
height
suitable for manufacture. On switching the drive 18, the holders 14 start to
rotate about
their axes together with the wafers 29. Simultaneously, the control system 5
is used to
regulate the dynamics of the wafer movement. The generator 10 of the plasma
jet 11
and the angular displacement drive 12 are switched and treatment is performed.
After a prescribed number of contacts of the wafer 29 with the plasma jet 11
of
the generator 10, the drive 12 is brought to a halt, under the predetermined
program
from the control system 5, so that none of the wafers 29 in the holders 14
falls within
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the zone of action of the generator plasma jet. The drive 18 and the generator
10 are
then turned off.
The cycle may then be repeated with the next batch of wafers.
Various modifications may be made to this device and to this embodiment
without departing from the spirit or scope of the general inventive concept as
defined
by the appended claims.
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