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FIELD OF THE INVENTION
The present invention relates to a microwave introducing device provided
with an endless circular waveguide and to a plasma treating apparatus
provided with said microwave introducing device. More particularly, the
present invention relates to a microwave introducing device capable of
uniformly and efficiently supplying a microwave from the entire
circumferential wall of a vacuum vessel into which a microwave is to be
introduced toward the center of said vacuum vessel and to a plasma
treating apparatus provided with said microwave introducing device.
BACKGROUND OF THE INVENTION
There are known a number of plasma treating apparatus in which a microwave
is used as the excitation source for generating plasma. Specific examples
of such plasma apparatus are CVD apparatus, etching apparatus, and the
like.
The formation of a deposited film using a so-called microwave plasma CVD
apparatus is conducted, for example, in such a manner as will be described
in the following. That is, a film-forming raw material gas is introduced
into the film-forming chamber of the microwave plasma CVD apparatus, and
at the same time, a microwave energy is introduced thereinto, whereby the
film-forming raw material gas is excited and decomposed with the action of
the microwave energy to produce plasma, resulting in causing the formation
of a deposited film on a substrate placed in the film-forming chamber.
The etching treatment of a substrate to be treated using a so-called
microwave plasma etching apparatus is conducted, for example, in such a
manner as will be described in the following. That is, an etching raw
material gas is introduced into the treating chamber of the microwave
plasma etching apparatus, and at the same time, a microwave energy is
introduced thereinto, whereby the etching raw material gas is excited and
decomposed with the action of the microwave energy to produce plasma,
resulting in etching the surface of said substrate with the plasma in the
treating chamber.
In each of these microwave plasma treating apparatus, a microwave is used
as the excitation source for the raw material gas used, and because of
this, it is possible to chain-like accelerate and excite electrons
generated as a result of ionizing the molecules of the raw material gas by
an electric field with an extremely large frequency. In this respect, the
microwave plasma treating apparatus has advantages such that a high
excitation efficiency and a high decomposition efficiency can be attained
as for the raw material gas, plasma with a high density can be relatively
easily produced, and the plasma treatment of an object can be conducted at
a high speed. In addition, there are further advantages in that the
microwave plasma treating apparatus can be designed to be of a
non-electrode discharging type because the microwave used has a property
of transmitting through a dielectric material and in that case, the plasma
treatment of an object can be conducted in a highly clean atmosphere.
The introduction of a microwave into these microwave plasma treating
apparatus is usually conducted by one of the following three manners. That
is, (i) a manner of introducing a microwave transmitted through a
waveguide from a microwave power source into the plasma treating chamber
through a coaxial antenna, (ii) a manner of introducing a microwave
transmitted through a waveguide from a microwave power source into the
plasma treating chamber through a dielectric window, and (iii) a manner of
introducing a microwave transmitted through a waveguide from a microwave
power source into the plasma treating chamber through one or more slots
(that is, one or more apertures) disposed at said waveguide. There are
known a number of plasma treating apparatus for subjecting an object to
plasma treatment, in which these microwave introducing manners are
employed.
As an example of the apparatus in which the above manner (i) is employed,
there can be mentioned a plasma treating apparatus of the constitution in
which a microwave is introduced into a plasma generation chamber through a
coaxial antenna which is described, for example, in Japanese Laid-open
patent application No. 131175/1980. The plasma treating apparatus
described in this publication is of the constitution schematically shown
in FIG. 10. The plasma treating apparatus shown in FIG. 10 comprises a
vacuum vessel 2105 having an electrically insulative cylinder 2116
installed therein, said insulative cylinder 2116 having a plurality of
specimens 2117 spacedly arranged on the inner wall face thereof. A
microwave outputted by a microwave oscillation source 2101 is introduced
into the vacuum vessel 2105 through a waveguide 2102 and an antenna 2121
made of a metal. When the microwave is introduced into the vacuum vessel
2105, plasma 2125 is produced between a cylindrical body 2122 made of a
quartz and the insulative cylinder 2116, wherein the specimens 2117 are
treated with the plasma generated. In FIG. 10, reference numeral 2106
indicates an exhaust pipe, reference numeral 2107 indicates a gas feed
pipe, and reference numeral 2124 indicates cooling gas which is flown in
the inside of the metallic antenna 2121. The above publication describes
that according to the apparatus shown in FIG. 10, a plasma region of an
area which is larger that the diameter of the waveguide 2102 can be formed
in the space surrounding the antenna 2124, and the gas pressure of the
plasma can be controlled to a large extent.
However, in the case of the plasma treating apparatus of the constitution
shown in FIG. 10, the coaxial antenna is always positioned within the
plasma generation chamber and because of this, a given inside area of the
plasma generation chamber which is occupied by the coaxial antenna is not
dedicated for the plasma treatment. Therefore, there is a limit for the
capacity of the inside area of the plasma generation chamber which can be
dedicated for the plasma treatment. Hence, this plasma treating apparatus
hardly satisfies the requirement of establishing a high density plasma
region of a large area as much as possible within a limited capacity so
that the plasma can be efficiently utilized. In addition, the density of
an electric power which can be applied to the coaxial antenna is governed
by the size thereof and therefore, there is a restriction for the density
of an electric power which can be applied to the coaxial antenna. In view
of this, it is almost impossible for this plasma treating apparatus to
attain high speed plasma treatment in which it is required to apply a
microwave with a great electric power.
As an example of the apparatus in which the above manner (ii) is employed,
there can be mentioned a plasma CVD apparatus of the constitution in which
a microwave is introduced into a plasma generation chamber through a
dielectric window which is described, for example, in Japanese Laid-open
patent application No. 186849/1985.
The plasma CVD apparatus disclosed in said publication No. 186849/1985 is
of the constitution shown in FIG. 11. The plasma CVD apparatus shown in
FIG. 11 comprises a vacuum vessel as a deposition chamber 2222 in which a
plurality of rotary shafts 2238 are spacedly arranged in parallel with
each other, and a cylindrical drum member 2212 is positioned on each of
said plurality of rotary shafts such that it can be rotated. The
cylindrical drum members 2212 are rotated by a driving chain 2264
extending from a motor 2250. In FIG. 11, there are shown only two
cylindrical drum members, but in practice, six cylindrical drum members
2212 are concentrically arranged while maintaining an equal interval
between each adjacent cylindrical drum members to establish an inside
chamber 2232 circumscribed by the six cylindrical drum members. The plasma
CVD apparatus is hermetically provided with a microwave transmissive
window 2296 which is situated above the inside chamber 2232. Reference
numeral 2272 indicates a microwave power source. A microwave energy from
the microwave power source is introduced into the inside chamber 2232
through an antenna probe 2276, waveguides 2280 and 2284, and the microwave
transmissive window 2296. Similarly, the plasma CVD apparatus is
hermetically provided with another microwave transmissive window 2294
which is situated below the inside chamber 2232. Reference numeral 2270
indicates another microwave power source. A microwave energy from this
microwave power source is introduced into the inside chamber 2232 through
an antenna probe 2274, waveguides 2278 and 2282, and the microwave
transmissive window 2294.
The formation of a deposited film in this plasma CVD apparatus is
conducted, for example, in the following manner. That is, the inside of
the vacuum vessel 2222 is evacuated to a desired vacuum degree through an
exhaust pipe 2224. Thereafter, raw material gases are introduced into the
inside chamber 2232 through gas feed pipes 2226 and 2228. Microwave energy
is then introduced into the inside chamber 2232 from the above and below
sides, wherein the raw material gases introduced therein are decomposed to
produce plasma 2268, whereby causing the formation of a semiconductor film
for electrophotography on the surface of each of the cylindrical drum
members 2212 each being maintained at a desired temperature by a heater
2200. The above publication describes that according to this plasma CVD
apparatus, there can be formed a uniform deposited film on each of the
cylindrical drum members 2212 at a high raw material gas utilization
efficiency. However, in practice, there are disadvantages for the plasma
CVD apparatus shown in FIG. 11 such that since the apparatus is of such
constitution that microwave is introduced into the inside chamber 2232
from the above and below sides, the density of plasma generated in the
vicinity of each of the microwave transmissive windows 2296 and 2294
unavoidably becomes higher than the density of plasma generated at the
central part of the inside chamber 2232 and because of this, it is
extremely difficult to form a uniform plasma region with a uniform density
in the space of the inside chamber 2232, and as a result, the resulting
deposited film on each of the cylindrical drum members 2212 varies in
terms of film property between the film deposited on each of the opposite
end portions of the cylindrical drum member 2212 and the film deposited on
the central portion thereof. The plasma CVD apparatus shown in FIG. 11
also has a disadvantage such that since a microwave is introduced through
each of the opposite microwave transmissive windows 2296 and 2294, it is
necessary to appropriately adjust the microwave propagation mode and the
position of each of the opposite waveguides such that the microwave
introduced through one of the opposite microwave transmissive windows is
prevented from transmitting through the other microwave transmissive
window to get into the waveguide and the microwave power source.
As an example of the apparatus in which the above manner (iii) is employed,
there can be mentioned a plasma treating apparatus of the constitution in
which a microwave is introduced into a plasma generation chamber through
slots (that is apertures) disposed at a waveguide which is described, for
example, in Japanese Laid-open patent application No. 30420/1991. The
plasma CVD apparatus described in this publication comprises a
film-forming chamber (that is, a plasma generation chamber) having a
circumferential wall formed by curving a web member as said web member is
continuously moving in the longitudinal direction, in which a deposited
film is formed on the inner wall face of the film-forming chamber. FIG. 12
is a schematic explanatory view illustrating the configuration of a
circular waveguide 2301 which is used for introducing a microwave into the
film-forming chamber of the plasma CVD apparatus. The circular waveguide
2301 has an end portion 2303 and a plurality of slots (that is, apertures)
2304 to 2308 being spacedly formed through one side thereof. A microwave
transmitted from the direction expressed by an arrow is introduced into
the film-forming chamber through the slots 2304 to 2308. The above
publication describes that according to this plasma CVD apparatus, it is
possible to continuously and uniformly form a large area of deposited
film, and the thickness of the deposited film formed can be properly
controlled by adjusting the transportation speed of the web member.
However, there are disadvantages for this plasma CVD apparatus such that
the density of plasma generated in the vicinity of the slots disposed at
the waveguide 2301 in the film-forming chamber is remarkably higher than
that of plasma generated in other regions in the film-forming chamber and
because of this, it is extremely difficult to produce plasma in a uniform
state in the film-forming chamber, and therefore, a well-skilled technique
is required in order to form a homogenous and uniform deposited film on a
large area web member. Incidentally, the circular waveguide 2301 is of the
constitution in that the end portion 2303 is provided to terminate
propagation of the microwave.
SUMMARY OF THE INVENTION
The principal object of the present invention is to eliminate the foregoing
problems of the known microwave introducing devices and to provide an
improved microwave introducing device capable of uniformly and efficiently
introducing a microwave into a vacuum vessel into which a microwave is to
be introduced through the periphery thereof.
Another object of the present invention is to provide an improved microwave
introducing device provided with a plurality of slots capable of uniformly
and efficiently introducing a microwave into a vacuum vessel through the
periphery of said vacuum vessel.
A further object of the present invention is to provide an improved
microwave introducing device provided with a plurality of slots capable of
dividing a microwave transmitted into two directions and interfering the
divided microwaves with each other which enables uniform and efficient
introduction of microwave into a vacuum vessel through the periphery of
said vacuum vessel.
A further object of the present invention is to provide an improved plasma
treating apparatus provided with the above-described microwave introducing
device which can conduct uniform and efficient plasma treatment for an
object to be treated.
A further object of the present invention is to provide an improved plasma
treating apparatus provided with the above-described microwave introducing
device which can to localize a region for plasma to be generated and which
enables to conduct uniform and efficient plasma treatment for an object to
be treated, which is arranged to isolate from the said plasma generation
region, without suffering from damages by the plasma.
A further object of the present invention is to provide an improved plasma
treating apparatus provided with the above-described microwave introducing
device further comprising means for generating a magnetic field, said
magnetic field generating means being disposed respectively at a given
position of said microwave introducing device in the vicinity of the slots
and in parallel to the inner wall face of the plasma generation chamber,
said improved plasma treating apparatus being capable of conducting
uniform and efficient plasma treatment for an object to be treated.
A further object of the present invention is to provide an improved plasma
treating apparatus provided with the above-described microwave introducing
device which can efficiently form a desirable semiconductor film or a
desirable insulative film excelling in uniformity.
A further object of the present invention is to provide an improved plasma
treating apparatus provided with the above-described microwave introducing
device which can localize a region for plasma to be generated and can
uniformly and efficiently form a deposited film on a substrate, which is
arranged to isolate from the said plasma generation region, without
suffering from damages by the plasma.
A further object of the present invention is to provide an improved plasma
treating apparatus provided with the above-described microwave introducing
device which can uniformly and efficiently form a high quality deposited
film on a web member or a lengthy substrate each having a relatively large
width.
In order to eliminate the foregoing problems of the known microwave
introducing devices and the known plasma treating apparatus provided with
such microwave introducing devices and in order to attain the above
objects, the present inventor made various studies through experiments
which will be later described. As a result, the present inventor obtained
a finding of the outline that in the case of using a microwave introducing
device comprising an endless circular waveguide, which can be arranged to
circumscribe vacuum vessel, and a means for introducing a microwave from a
microwave power source into the circular waveguide wherein a plurality of
slots each having a given shape are spaced at a given equal interval at
the inner side of the circular waveguide, a microwave can be uniformly and
efficiently introduced into a vacuum vessel through the periphery thereof.
The present inventor obtained another finding that in the case of using a
plasma treating apparatus in which said microwave introducing device is
installed, an object to be treated which is positioned in a plasma
generation space of the plasma treating apparatus can be uniformly and
efficiently treated with plasma with plasma generated therein. The present
inventor obtained a further finding that in the case of using a plasma
treating apparatus in which the above microwave introducing device is
installed, plasma can be produced in a localized state, and an object to
be treated which is arranged to isolate from the region where the plasma
is generated can be treated without suffering from damages by the plasma.
The present inventor obtained a further finding that in the case of using
a plasma treating apparatus in which the above microwave introducing
device is installed, a high quality deposited film can be uniformly and
efficiently formed on a substrate. The present inventor obtained a further
finding that in the case of using a plasma treating apparatus in which the
above microwave introducing device is installed, plasma can be produced in
a localized state, and a high quality deposited film can be uniformly and
efficiently formed on a substrate on which a film is to be deposited,
which is arranged to isolate from the region where the plasma is
generated, without suffering from damages by the plasma. The present
inventor obtained a further finding that in the case of using a plasma
treating apparatus in which the above microwave introducing device is
installed, a high quality deposited film can be uniformly and efficiently
formed on a web member or a lengthy substrate each having a relatively
large width.
The present invention has been accomplished based on the above findings
obtained by the present inventor through the experiments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1(A) is a schematic view illustrating an example of a microwave
introducing device according to the present invention.
FIG. 1(B) is a schematic explanatory view of an apparatus employed in the
experiments conducted upon accomplishing the present invention.
FIG. 2(A) is a schematic view illustrating the configuration of an example
of a microwave introducing device according to the present invention.
FIG. 2(B) is a graph showing the results obtained in Experiment 1 which was
conducted upon accomplishing the present invention.
FIG. 2(C) is a graph showing the results obtained in the comparative test
in Experiment 1, which was conducted upon accomplishing the present
invention.
FIG. 3(A) is a schematic view illustrating the configuration of another
example of a microwave introducing device according to the present
invention.
FIG. 3(B) is a graph showing the results obtained in Experiment 2 which was
conducted upon accomplishing the present invention.
FIG. 3(C) is a graph showing the results obtained in Experiment 3 which was
conducted upon accomplishing the present invention.
FIG. 4(A) is a schematic view illustrating the configuration of a further
example of a microwave introducing device according to the present
invention.
FIG. 4(B) is a graph for explaining the principles of the microwave
introducing device used in Experiment 4 which was conducted upon
accomplishing the present invention.
FIG. 4(C) is a graph explaining the measured results with regard to plasma
density distribution in the circuit direction.
FIG. 5(A) is a schematic view illustrating the configuration of a further
example of a microwave introducing device according to the present
invention.
FIG. 5(B) is a graph showing the results obtained in Experiment 5 which was
conducted upon accomplishing the present invention.
FIG. 6(A) is a schematic view illustrating the configuration of a further
example of a microwave introducing device according to the present
invention.
FIG. 6(B) is a graph showing the results obtained in Experiment 6 which was
conducted upon accomplishing the present invention.
FIG. 7(A) is a schematic view illustrating an example of a plasma treating
apparatus according to the present invention.
FIG. 7(B) is a schematic view illustrating another example of a plasma
treating apparatus according to the present invention.
FIG. 8(A) is a schematic view illustrating a further example of a plasma
treating apparatus according to the present invention.
FIG. 8(B) is a schematic view illustrating a further example of a plasma
treating apparatus according to the present invention.
FIG. 9(A) is a schematic view illustrating a further example of a plasma
treating apparatus according to the present invention.
FIG. 9(B) is a schematic view illustrating a further example of a plasma
treating apparatus according to the present invention.
FIG. 10 is a schematic view for explaining the known coaxial antenna type
microwave introducing device.
FIG. 11 is a schematic view for explaining the known transmissive window
type microwave introducing device.
FIG. 12 is a schematic view for explaining the known slot type microwave
introducing device.
Description will be made of embodiments of a microwave introducing device
according to the present invention which is of any of the following
configuration and of embodiments of a plasma treating apparatus provided
with such microwave introducing device according to the present invention.
1. Microwave Introducing Device
The microwave introducing device according to the present invention
includes Embodiment 1-(1) to Embodiment 1-(5) which will be described
below.
Embodiment 1-(1)
A microwave introducing device comprising a waveguide and means for
introducing a microwave from a microwave power source into said waveguide,
characterized in that said waveguide is an endless circular waveguide, and
a plurality of slots each having a given shape are spaced at the inner
side face of said circular waveguide at a given equal interval.
Embodiment 1-(2)
A microwave introducing device comprising a waveguide and means for
introducing a microwave from a microwave power source into said waveguide,
characterized in that said waveguide is an endless circular waveguide, and
a plurality of slots each having a given shape are spaced at the inner
side face of said circular waveguide at an equal interval corresponding to
a 1/4 of the guide wavelength of said microwave.
Embodiment 1-(3)
A microwave introducing device comprising a waveguide and means for
introducing a microwave from a microwave power source into said waveguide,
characterized in that said waveguide is an endless circular waveguide, a
plurality of slots each having a given shape are spaced at the inner side
face of said circular waveguide at a given equal interval, and said
microwave introducing means is disposed to direct to the tangential
direction of said circular waveguide.
Embodiment 1-(4)
A microwave introducing device comprising a waveguide and means for
introducing a microwave from a microwave power source into said waveguide,
characterized in that said waveguide is an endless circular waveguide, a
plurality of slots each having a given shape are spaced at the inner side
face of said circular waveguide at an equal interval, and said plurality
of slots are designed such that their length in the direction
perpendicular to the direction of the microwave to transmit is gradually
increased along the direction of the microwave to transmit.
Embodiment 1-(5)
A microwave introducing device comprising a waveguide and means for
introducing a microwave from a microwave power source into said waveguide,
characterized in that said waveguide is an endless circular waveguide, a
plurality of slots each having a given shape are spaced at the inner side
face of said circular waveguide at a given equal interval, and said
microwave introducing means is provided with means capable of dividing
said microwave into two directions so that the microwave transmits in
opposite directions in the circular waveguide.
2. Plasma Treating Apparatus
The plasma treating apparatus according to the present invention includes
Embodiment 2-(1) to Embodiment 2-(8) each being provided with one of the
microwave introducing devices described in the above Embodiments 1-(1) to
1-(5) which will be described below.
Embodiment 2-(1)
A plasma treating apparatus comprising a plasma generation chamber capable
of being vacuumed and a microwave introducing means, said microwave
introducing means being arranged along the periphery of said plasma
generation chamber so as to circumscribe said plasma generation chamber,
said microwave introducing means comprising one of the microwave
introducing devices described in the foregoing Embodiments 1-(1) to 1-(5),
wherein a microwave is uniformly introduced into said plasma generation
chamber through the circumferential wall thereof to generate plasma in
said plasma generation chamber whereby an object to be treated which is
positioned in said plasma generation chamber is treated with the plasma.
Embodiment 2-(2)
A plasma treating apparatus comprising a plasma generation chamber capable
of being vacuumed, a microwave introducing means which is arranged along
the periphery of said plasma generation chamber so as to circumscribe said
plasma generation chamber, and a treating chamber which is isolated from
but is communicated with said plasma generation chamber, said microwave
introducing means comprising one of the microwave introducing devices
described in the foregoing Embodiments 1-(1) to 1-(5), wherein a microwave
is uniformly introduced into said plasma generation chamber through the
circumferential wall thereof to generate plasma containing active species
in said plasma generation chamber, said active species are introduced into
said treating chamber wherein an object to be treated which is positioned
therein is treated with the active species.
Embodiment 2-(3)
A plasma treating apparatus comprising a plasma generation chamber capable
of being vacuumed and a microwave introducing means which is arranged
along the periphery of said plasma generation chamber so as to
circumscribe said plasma generation chamber, said microwave introducing
means comprising one of the microwave introducing devices described in the
foregoing Embodiments 1-(1) to 1-(5), said plasma generation chamber being
provided with a plurality of magnetic field generating means each being
disposed at a given position thereof in the vicinity of the slots and in
parallel to the inner wall face of the plasma generation chamber, wherein
a microwave is uniformly introduced into said plasma generation chamber
through the circumferential wall thereof to generate plasma in said plasma
generation chamber whereby an object to be treated which is positioned in
said plasma generation chamber is treated with the plasma.
Embodiment 2-(4)
A plasma treating apparatus comprising a plasma generation chamber capable
of being vacuumed, a microwave introducing means which is arranged along
the periphery of said plasma generation chamber so as to circumscribe said
plasma generation chamber, and a treating chamber which is isolated from
but is communicated with said plasma generation chamber, said microwave
introducing means comprising one of the microwave introducing devices
described in the foregoing Embodiments 1-(1) to 1-(5), said plasma
generation chamber being provided with a plurality of magnetic field
generating means each being disposed at a given position thereof in the
vicinity of the slots and in parallel to the inner wall face of the plasma
generation chamber, wherein a microwave is uniformly introduced into said
plasma generation chamber through the circumferential wall thereof to
generate plasma containing active species in said plasma generation
chamber, said active species are introduced into said treating chamber
wherein an object to be treated which is positioned therein is treated
with the active species.
Embodiment 2-(5)
A plasma treating apparatus comprising a plasma generation chamber capable
of being vacuumed and a microwave introducing means, said microwave
introducing means being arranged along the periphery of said plasma
generation chamber so as to circumscribe said plasma generation chamber,
said microwave introducing means comprising one of the microwave
introducing devices described in the foregoing Embodiments 1-(1) to 1-(5),
wherein a microwave is uniformly introduced into said plasma generation
chamber through the circumferential wall thereof to generate plasma in
said plasma generation chamber whereby a cylindrical substrate as the
object to be treated is treated with the plasma without moving said
cylindrical substrate or while moving said cylindrical substrate in
parallel to the central axis thereof.
Embodiment 2-(6)
A plasma treating apparatus comprising a plasma generation chamber capable
of being vacuumed and a microwave introducing means, said microwave
introducing means being arranged along the periphery of said plasma
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