DESCRIPTION
THIN FILM FORMING METHOD AND DEVICE, AND THIN FILM
FORMING PROCESS MONITORING METHOD AND DEVICE
TECHNICAL FIELD
The present invention relates to a thin film forming method and to a thin film
forming device for forming a thin film, which is made of an oxide, on a substrate such as a
plastic container. Also, the present invention relates to a thin film forming process
monitoring method and to a thin film forming device for forming a silicon oxide thin film
on a surface of a substrate by plasmatizing a mixture gas including an organosilicon
compound gas and an oxidizing gas.
BACKGROUND ART
Plastic containers are used for packaging and containing purposes in various
fields such as beverages, foods, toiletry goods, and medicines because they not only have
a superior hardness, light weight, and superior moldability, but are also cost efficient,
difficult to break, and easy to re-seal.
Although plastic containers have these advantages, plastic containers also have
disadvantages in that a low molecular gas such as oxygen and carbon dioxide can be
transmitted therethrough. Such a disadvantage is called low gas impermeability because
gas impermeability is low. Occasionally, some of the contents in the container are
affected undesirably by such gases. Here, various attempts for improving the gas
impermeability of plastics have been made when producing containers industrially.
Among such attempts, one method is realized, in which a material having a high gas
impermeability and made of an inexpensive common material is formed in a multi-layer
structure.
However, it is difficult to recycle a material having a multi-layered structure
which consists of at least two kinds of material. Thus, there was a problem from an
ecological point of view because a material having a multi-layer structure must be
discarded after usage. Therefore, other attempts have been made for reducing a material
having a high gas impermeability as much as possible until the material having a high gas
impermeability has no effect on recycling. However, quite often, it was not possible to
realize a desirable gas impermeability in a material having a multi-layer structure.
Currently, in order to realize a recycling ability and gas impermeability to
oxygen, carbon monoxide, and steam, a method has been proposed in which a thin film
having gas impermeability is formed on the inner surface of a container made by
commonly-used plastics. One thin film forming method is a plasma-assisted CVD
method, in which a thin film is formed on the inner surface of a container by plasmatizing
a process gas and reacting the process gas chemically. Specifically, the plasma-assisted
CVD method, in which a container is disposed between a hollow high frequency electrode
having a shape which is approximately the same as the outer shape of the container, and an
inner electrode having a shape which is approximately the same as the inner shape of the
container, is known in the art (see, for example, patent document 1). As another form
of the plasma-assisted CVD method, both the high frequency electrode and the inner
electrode are disposed away from a surface of the container by approximately the same
distance (see a patent document 2).
Patent Document 1: Japanese Unexamined Patent Application, First Publication No.
H8-53117
Patent Document 2: Japanese Unexamined Patent Application, First Publication No.
H8-175528
However, even if a thin film is formed by these methods, it is still difficult to
control strictly flow ratio of a reactive gas and a monomer gas in the plasmatized process
gas. As a result, there has been a problem in that it was not possible to stably form a thin
film having a sufficient gas impermeability, and in that, the gas impermeability varied
even among the produced containers. Furthermore, there has been another problem in
that the gas impermeability of the thin film decreases because the produced thin film does
not have sufficient flexibility, and finally, cracking occurs on the thin film when using the
container.
Also, a thin film has been formed on the inner surface of not only plastic
container, but also, for example, glass container in order to prevent lead, cadmium, etc.,
from melting in the contents of the containers. For that case, it is necessary to form the
thin film stably without variation.
Also, a thin film having gas impermeability has been formed on the inner surface
of plastic containers in order to add gas impermeability. For that purpose, a
plasma-assisted CVD method (hereinafter, a plasma CVD method), in which a thin film is
formed on the inner surface of the plastic container by plasmatizing a process gas and
reacting the plasmatized process gas chemically, is known in the art.
It was not possible to know whether or not the thin film has a desirable surface
quality during forming the thin film by the plasma CVD method. Therefore,
conventionally, a thin film has been produced while monitoring parameters (for example,
degree of vacuum, applied power, and introduced gas flow amount), and after that,
whether or not the produced thin film had a desirable surface quality has been evaluated.
However, the monitoring of the parameters, such as the degree of vacuum, applied power,
and introduced gas flow amount, has not yet achieved the desirable surface quality of the
produced thin film. Therefore, a more improved process monitoring method is needed.
For that purpose, a method in which a plasma emission is monitored has been
proposed. This method is called a plasma diagnosis, in which it is possible to obtain
information concerning the actual inner structure of a plasma by monitoring emission of
the plasma. By employing this method, it is possible to forecast the surface quality of the
thin film accurately.
For example, a method is proposed in which whether or not a process is
conducted properly is determined by monitoring a ratio between the intensity of hydrogen
alpha rays and the intensity of hydrogen beta rays, which are radiated from a plasma, or by
monitoring a ratio between the hydrogen alpha rays or beta rays, and the intensity of
helium radiation, in Japanese Unexamined Patent Application, First Publication No.
H1-87777 (patent document 3).
However, the method which is disclosed in Japanese Unexamined Patent
Application, First Publication No. H1-87777, has the following problems.
Firstly, although the hydrogen alpha rays have a relatively large intensity, the
hydrogen beta rays have a small intensity, and the hydrogen beta ray vary greatly.
Therefore, when the ratio between the intensity of the hydrogen beta rays and the intensity
of the radiation of other atomic specimen (molecular specimen) is calculated, the
calculated ratio varies greatly; thus, it is difficult to know the inner structure of the plasma
accurately.
Also, even if the ratio of the intensities is calculated between relatively intense
rays such as the hydrogen alpha rays and the helium radiation, both the intensity of the
hydrogen alpha rays and the intensity of the helium radiation fluctuate similarly if the thin
film forming pressure fluctuates. Therefore, even if the thin film forming pressure
fluctuates and the surface quality of the produced thin film fluctuates accordingly, the ratio
between the intensity of the hydrogen alpha rays and the intensity of the helium radiation
does not vary greatly. Therefore, there is a problem in that it is not possible to monitor
the plasma accurately.
Also, the spectrum of the plasma is measured in a wide range from a visible
wavelength to a near-visible wavelength (see FIG. 3 in patent document 3). There is a
problem because a specific complicated spectrometer is necessary for such a
measurement, and such a spectrometer is expensive.
Patent Document 3: Japanese Unexamined Patent Application, First Publication No.
Hl-87777.
DISCLOSURE OF INVENTION
The present invention was conceived in view of the above circumstances, and an
object thereof is to provide a thin film forming method and a thin film forming device,
which can achieve a stable gas impermeability and a desirable flexibility in a thin film
without variation in surface quality even if the thin film is formed onto a large number of
substrates.
Another object thereof is to provide a thin film forming process monitoring
method, and a thin film forming device, by which it is possible to know the structure of a
generated plasma more accurately, and to know whether or not the produced thin film has
a desirable surface quality during the process in which a mixture gas consisting of an
organosilicon compound gas and an oxidizing gas is plasmatized, and a silicon oxide thin
film is formed on a surface of the substrate.
In the present invention, a thin film forming method for plasmatizing a mixture
gas which consists of a monomer gas and an oxidizing reactive gas, and forming a thin
film which is made of an oxide, on a surface of a substrate, includes: a first step of
forming a first thin film by plasmatizing the mixture gas while varying the flow amount
ratio of the monomer gas with respect to the reactive gas under the condition that the flow
amount ratio is in at least a specific range.
In the first thin film forming step, it is preferable to decrease the supply flow
amount ratio continuously.
In the first thin film forming step, it is preferable that an initial value of the
supply flow amount ratio in the first thin film forming step be in a range of 0.02 to 0.2.
It is preferable that the thin film forming method further includes a second thin
film forming step in which the supply flow amount ratio increases after the first thin film
forming step.
Also, in the thin film forming method, it is preferable that the plasmatization be
conducted while generated reflected power is controlled so as to be equal to 10% or less
than a supplied high frequency power by passing the high frequency power which is 100
MHz or lower through a impedance matching network before being supplied to a high
frequency electrode.
In the present invention, the thin film forming device for plasmatizing a mixture
gas which consists of a monomer gas and an oxidizing reactive gas, and for forming a thin
film which is made of an oxide, on an inner surface of a cylindrical container having a
closed end, includes: a plurality of thin film forming chambers, each of the thin film
forming chambers being provided with a cylindrical high frequency electrode, one end of
the high frequency electrode being closed such that the cylindrical container can be
disposed on the inner surface of the high frequency electrode, and a ground electrode
disposed in the cylindrical container, the ground electrode having a gas generating port on
a tip section of the ground electrode such that the gas generating port generates the
mixture gas; a high frequency power supply section having an impedance matching
network and a high frequency power supply such that high frequency power can be
supplied to the high frequency electrode through the impedance matching network; and a
flow amount control section for controlling the flow amount ratio of the monomer gas and
the reactive gas contained in the mixture gas. In this case, the high frequency power is
supplied to a plurality of the thin film forming chambers from a high frequency power
supply section.
It is acceptable if a detachable spacer which is formed by an insulative member is
disposed between the cylindrical container and the high frequency electrode.
It is preferable that the gas generating port have at least a hole of which the
diameter is 0.5 mm or smaller and/or a slit of which the width is 0.5 mm or narrower.
Also, it is preferable that an average surface roughness of the outer surface of the
ground electrode be 5 to 50 µm, or that a detachable cover pipe be provided on at least a
part of the outer periphery of the ground electrode and that an average surface roughness
of the outer surface of the cover pipe be 5 to 50 µm.
Also, it is preferable that a metal member or a ceramic member be sprayed onto
the outer surface which has the average surface roughness.
Also, in the present invention, a thin film forming process monitoring method for
plasmatizing a mixture gas consisting of an organosilicon compound gas and an oxidizing
gas, and for forming a silicon oxide thin film on a surface of a substrate includes the steps
of: measuring the intensity of hydrogen alpha rays which are radiated from the plasma and
the intensity of an oxygen radiation rays; comparing the intensity of the hydrogen alpha
rays and the intensity of the oxygen radiation rays with the intensity of the hydrogen alpha
rays and the intensity of the oxygen radiation rays which have been measured under the
condition that the silicon oxide thin film has a desirable surface quality; and determining
whether or not the silicon oxide thin film which has a desirable surface quality is formed.
Here, it is preferable that the intensity of the hydrogen alpha rays and the
intensity of the oxygen radiation rays be measured by separating radiation rays which have
a specific range of wavelengths among radiation rays which are radiated from the plasma
and measuring the intensity thereof.
Also, it is preferable that the intensity of the hydrogen alpha rays and the
intensity of the oxygen radiation rays be measured by measuring the intensity of radiation
rays which have a wavelength in the range of 656 ±5 nm and the intensity of radiation rays
which have a wavelength range of 777± 5 nm among the radiation rays which are radiated
from the plasma.
Also, in the present invention, the thin film forming device includes: a chamber
for plasmatizing a mixture gas, the mixture gas which consists of an organosilicon
compound gas and an oxidizing gas, and for forming a silicon oxide thin film on a surface
of a substrate; a measuring section for measuring the intensity of hydrogen alpha rays and
the intensity of oxygen radiation rays, both of the rays being radiated from the plasma in
the chamber; a storage section for storing the intensity of the hydrogen alpha rays and the
intensity of the oxygen radiation rays such that the organosilicon thin film has a
predetermined desirable surface quality; and a determining section for determining
whether or not the intensity of the measured hydrogen alpha rays and the intensity of the
measured oxygen radiation rays are within specific ranges, by comparing the intensity of
the measured hydrogen alpha rays with the intensity of the hydrogen alpha rays in the
storage section, and by comparing the intensity of the oxygen radiation rays measured by
the measuring section with the intensity of the oxygen radiation rays which is stored in the
storage section.
Here, it is preferable that the measuring section be provided with a bandpass filter
which separate only radiation rays which have a specific wavelength range from among
the radiation rays which are radiated from the plasma in the chamber.
Also, it is preferable that the measuring section include a first bandpass filter of
which the transmittance of the radiation rays which have a wavelength range outside 656
±5 nm is 1% or lower, a second bandpass filter of which transmittance of the radiation
rays which have a wavelength range outside 777 ±5 nm is 1% or lower, a first quantity
sensor which receives the radiation rays which pass through the first bandpass filter, and a
second quantity sensor which receives the radiation rays which pass through the second
bandpass filter.
BRIEF DESCRIPTION OF THE ACCOMPAYING DRAWINGS
FIG. 1 is a general view of an example of a first embodiment of a thin film
forming device.
FIG. 2 is a vertical cross section of a thin film forming chamber which is provided
in the thin film forming device shown in FIG. 1.
FIG. 3 is a plan view in which a gas generating port is formed in a ground
electrode on the thin film forming device shown in FIG. 1.
FIG. 4 is a graph which shows an example of the change of a supply flow amount
ratio with respect to time.
FIG. 5 is a graph which shows another example of the change of a supply flow
amount ratio with respect to time.
FIG. 6 is a plan view in which another example of the gas generating port is
formed in the ground electrode on the thin film forming device.
FIG. 7 is a vertical cross section in which an example of the ground electrode
which is provided with the thin film forming device is shown.
FIG. 8 is a plan view in which another example of the thin film forming chamber
is shown.
FIG. 9 is a general view of an example of the thin film forming device according
to the present invention.
FIG. 10 is a cross section in which an example of the thin film forming chamber
according to the present invention is shown.
FIG. 11 is a general view in which an example of a monitoring computer
according to the present invention is shown.
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment
Details of a first embodiment of the thin film forming method according to the
present invention are explained with respect to the examples below, in which a thin film
made of silicon oxide is formed on the inner surface of a plastic cylindrical container,
which has a circular cross section with a closed end.
FIG. 1 shows an example of a thin film forming device 10 which is preferably
used in the present embodiment of the thin film forming method. The thin film forming
device 10 is provided with four sets of thin film forming chambers 20 which enables
forming of thin films in the four sets of cylindrical containers 21 simultaneously by
disposing the cylindrical containers 21 in predetermined positions in the thin film forming
chambers 20.
As shown in FIG. 2, each of the thin film forming chambers 20 is provided with a
cylindrical high frequency electrode 22 having a circular cross section and a closed end,
and a tubular ground electrode 23 of which the tip section is introduced inside of the
cylindrical container 21 when the cylindrical container 21 is disposed in the predetermined
position inside the high frequency electrode 22.
In this example, the high frequency electrode 22 consists of a cylinder section 22a
which is formed from a conductive material, and a lid section 22b, which is formed from a
conductive material and which seals an end of the cylinder section 22a. The lid section
22b is detachable from the cylinder section 22a.
Also, the ground electrode 23 is formed from a conductive material. A gas
generating port 23a is formed on the tip section of the ground electrode 23 in order to
generate a process gas, such as a mixture gas including a monomer gas and an oxidizing
reactor, for forming silicon oxide toward the inside of the cylindrical container 21. The
mixture gas is generated from the gas generating port 23 a by introducing the monomer gas
and the reactive gas from the base end section. As explained above, in this example, the
ground electrode 23 serves as a gas introducing pipe for the process gas. Also, in this
example, as shown in FIG. 3, the gas generating port 23 a consists of five approximately
rectangular slits 23b having a 0.5 mm width.
A port section supporting port 24a for supporting a port section of the cylindrical
container 21, and an insulating plate 24 formed from a ceramic material for insulating the
high frequency electrode 22, are formed on the other end of the high frequency electrode
22. Also, a cylindrical bottom section 25, which has a gas exhausting port 25a for
exhausting air into the thin film forming chamber 20, is provided through this insulating
plate 24. By connecting a suction pump, which is not shown in the drawing, to the gas
exhausting port 25a, etc., it is possible to depressurize the inside of the thin film forming
chamber 20 and evacuate air therewithin. Here, a connection hole (not shown in the
drawing) which can connect a space between the cylindrical container 21 and the high
frequency electrode 22 and a space inside of the cylindrical container 21 is formed in the
insulating plate 24. When the suction pump starts, it is possible to depressurize not only
the space inside the cylindrical container 21 but also the space between the cylindrical
container 21 and the high frequency electrode 22. Here, the tip of the above explained
ground electrode 23 is introduced to the inside of the cylindrical container 21 through the
bottom section 25.
In FIG. 1, reference numeral 42 indicates four sets of flow amount control
sections, each of which consists of a mass-flow controller 40 for controlling the flow
amount of the reactive gas and a mass-flow controller 41 for controlling the flow amount
of the monomer gas. The mass-flow controllers 40 and 41 are provided in each of the
thin film forming chambers 20. The flow amount of the reactive gas and the flow
amount of the monomer gas are controlled by the flow amount control sections 42. After
that, the reactive gas and the monomer gas are introduced into each of the thin film
forming chambers 20 from the base end section of the ground electrode 23. By doing
this, the reactive gas and the monomer gas are generated from the gas generating port 23 a.
In addition, as shown in FIG. 1, the thin film forming device 10 is provided with a
high frequency power supply section 30 which can supply high frequency power to the
four sets of the thin film forming chambers 20 simultaneously.
The high frequency power supply section 30 is provided with a high frequency
power supply 31 for supplying high frequency power, and an impedance matching
network 32 for rectifying the high frequency power supplied from the high frequency
power supply 31. The high frequency power supplied from the high frequency power
supply 31 is adjusted while controlling a matching value, and supplied to the high
frequency electrode 22. By doing this, it is possible to avoid a reflected power; thus, the
supplied high frequency power is sent to the high frequency electrode 22 efficiently. As
a result, it is possible to form a thin film which has a desirable gas impermeability.
Next, an example of a method by which the thin films are formed on the four sets
of the cylindrical containers 21 by the thin film forming device 10 in this example, is
explained.
Firstly, the lid section 22b of the high frequency electrode 22 is removed in each
of the thin film forming chambers 20. The cylindrical container 21, as a substrate, is put
into the high frequency electrode 22. The port section of the cylindrical container 21 is
fitted to the port section supporting port 24a formed on the insulating plate 24. Next, the
lid section 22b is fitted to the cylindrical section 22a of the high frequency electrode 22 so
as to form a seal. Thus, the end of the high frequency electrode 22 is sealed. The gas
generating port 23 a, which is formed on the tip of the ground electrode 23, is disposed
inside of the cylindrical container 21. After that, a suction pump, which is not shown in
the drawing, is started. After air in the space inside of the thin film forming chamber 20
is depressurized until it is completely evacuated, a mixture gas, which consists of a
monomer gas and a reactive gas, is introduced into the thin film forming chambers 20
while controlling the flow amount of the monomer gas and the flow amount of the reactive
gas by means of the flow amount control sections 42. By doing this, the mixture gas is
generated from the gas generating port 23 a. Next, the high frequency power supply
section 30 is started, high frequency power, which is not greater than 100 MHz, is
transmitted through the impedance matching network 32. The high frequency power is
supplied to the high frequency electrode 22 in each of the thin film forming chambers 20
while varying the matching value, and controlling the generated reflected power to under
10% of the supplied high frequency power. As a result, the mixture gas is plasmatized
between the high frequency electrode 22 and the ground electrode 23 in each of the thin
film forming chambers 20; thus, a thin film, which is formed of silicon oxide is formed on
the inner surface of the cylindrical container 21.
In addition, in a first thin film forming step, a flow rate decreases continuously
and gradually from a large flow rate while a flow rate (supply flow amount ratio) of the
monomer gas, with respect to the reactive gas in the supplied mixture gas is included
within at least a specific range. By such a first thin film forming step, it is possible to
stably form a thin film which has a particularly high gas impermeability without variation.
The supply flow amount ratio is controlled by the flow amount control section 42.
In this example, the specific range indicates a range of a supply flow amount
ratio, by which a thin film having a desirable gas impermeability can be formed. The
specific range varies according to the type of the produced thin film, and the type of
employed mixture gas. The specific range of the supply flow amount ratio of the
monomer gas, with respect to the reactive gas, for forming a thin film having a desirable
gas impermeability is in a range of 0 to approximately 0.05, if a thin film of an silicon
oxide is formed under the condition that, if the mixture gas is formed from a monomer gas
and a reactive gas, the monomer gas is an organosilicon compound such as
hexamethyldisiloxane, and the reactive gas is oxygen.
Therefore, for example, as shown in the graph in FIG. 4, the initial value of the
supply flow amount ratio in the first thin film forming step is set at 0.1, which is greater
than the above specific range. After that, the mixture gas is supplied. After that, the
high frequency power is supplied from the high frequency power supply section 30. The
mixture gas is plasmatized between the high frequency electrode 22 and the ground
electrode 23. Next, the supply flow amount ratio is decreased continuously by
decreasing the flow amount of the monomer gas continuously by means of the flow
amount control section 42 while the plasmatization of the mixture gas is maintained.
Consequently, the flow amount of the monomer gas is decreased for approximately 5
seconds until the supply flow amount ratio is 0.01. By doing this, the supply flow
amount ratio decreases continuously from 0.1 to 0.01 in approximately 5 seconds. Thus,
there is a time period of 3.5 seconds in which the supply flow amount ratio is in a range of
0 to 0.05, in which it is possible to form a thin film having a desirable gas impermeability.
By a method in which the supply flow amount ratio is controlled variably and
continuously such that the supply flow amount ratio is included within at least the specific
range, it is possible to form a thin film having a desirable gas impermeability more easily
than the case of strictly controlling the supply flow amount ratio, forming a thin film
having a desirable gas impermeability, and plasmatizing the mixture gas while strictly
maintaining the supply flow amount ratio strictly. Also, it is very difficult to control the
supply flow amount ratio at a constant level every time the thin film is formed.
However, by the above method, it is possible to form a thin film repeatedly without strictly
controlling the flow amount strictly. Therefore, the quality of the produced thin films is
consistent even if a large number of thin films are produced on the cylindrical container
21.
The specific range is variable in accordance with the type of the employed
mixture gas and the purpose for forming the thin film. Therefore, there is no limitation
for the specific range and it is possible to set the specific range desirably. Also, the time
for controlling the supply flow amount ratio within the specific range is variable in
accordance with the type of the employed mixture gas and the purpose for forming the
thin film. Therefore, there is no limitation for the time and it is possible to set the time
desirably. However, it is preferable to maintain the supply flow amount ratio for 2 to 5
seconds within the above specific range in order to use an organosilicon compound such
as hexamethyldisiloxane as the monomer gas, and use oxygen as the reactive gas in order
to form a thin film, which is formed from silicon oxide having a desirable gas
impermeability. There is a case in which a thin film having a desirable gas
impermeability cannot be produced, if the time is shorter than 2 seconds. If the time
exceeds 5 seconds, the gas impermeability is not improve.
Also, in this example, as shown in FIG 4, the supply flow amount ratio decreases
continuously by two steps of different speed reductions. However, such a two-stepped
speed reduction is not an absolute requirement. For example, a three, or more-stepped
speed reduction is acceptable. Also, it is acceptable if the supply flow amount ratio
decreases at a constant decreasing speed. Also, as long as the supply flow amount ratio
varies while being included in at least the specific range, the supply flow amount ratio
may increase in the first thin film forming step. Also, it is acceptable if the supply flow
amount ratio varies while repeating the increase and the decrease alternately. However,
like this example, in the method for decreasing the supply flow amount ratio continuously,
a mixture gas having a high monomer gas density is plasmatized in the initial period of the
first thin film forming step. Therefore, a more organic thin film is formed on a surface of
the substrate. If the substrate is made of plastic, adhesion strength between the substrate
and the thin film can be improved.
Also, in this example, the initial value of the supply flow amount ratio starts at
0.1 in the first thin film forming step, and after that, the supply flow amount ratio
decreases. A preferable initial value for the supply flow amount ratio is 0.02 to 0.2.
More preferably, it is 0.02 to 0.1. If the supply flow amount ratio is smaller than 0.01,
the supply flow amount ratio probably cannot be included in the specific range; thus, it is
not possible to form a thin film having a desirable gas impermeability. On the other
hand, if the supply flow amount ratio exceeds 0.2, it will take an undesirably long time for
forming a thin film.
Also, in this example, the supply flow amount ratio is variable while the reactive
gas is supplied by an approximately constant flow amount, and only the supply flow
amount of the monomer gas decreases. According to this method, it is possible to form a
thin film having a desirable gas impermeability in a short time. In addition, the supply
flow amount may be decreased by various other methods. For example, it is acceptable
that the supply flow amount of the reactive gas increase while the supply flow amount of
the monomer gas is approximately constant. Also, it is acceptable that both the supply
flow amount of the monomer gas and the supply flow amount of the reactive gas vary
while the supply flow amount of the mixture gas is approximately constant. An optimum
value for the total supply flow amount of the mixture gas varies in accordance with the
capacity (exhausting speed) of the suction pump; therefore, it is preferable to set the total
supply now amount in accordance with the capacity of the suction pump.
Also, as explained above, in this example, the mixture gas is plasmatized while
the generated reflected power is controlled to be 10% or lower of the supplied high
frequency power 100 MHz or lower high frequency power through the impedance
matching network 32 and supplying the high frequency power to the high frequency
electrode 22 while varying the matching value. Therefore, even if the impedance of the
plasma varies because the supply flow amount ratio varies in the first thin film forming
step, it is possible to maintain a substantially high frequency power for plasmatizing the
mixture gas at an approximately constant level, and avoid the reduced gas impermeability
of the thin film due to an increase of the reflected power. If the reflected power is
maintained at 10% or lower, the gas impermeability of the produced thin film can be
maintained at a higher level.
Also, like in this example, in the case of forming a thin film made of a silicon
oxide, in a second thin film forming step, it is preferable that the supply flow amount ratio
of the monomer gas with respect to the reactive gas increase after the above-explained
first thin film forming step. By means of the second thin film forming step, it is possible
to form an organic film on the outside of the thin film formed in the first thin film forming
step. As a result, it is possible to form a thin film which has not only gas impermeability,
but also flexibility. Thus, cracks hardly occur during use of the cylindrical container 21.
In other to increas the supply flow amount ratio of the monomer gas with
respect to the reactive gas, a method in which only the supply flow amount of the
monomer gas increases is available. Also, a method in which only the supply flow
amount of the reactive gas decreases is available. In addition, a method is preferable in as shown in Fig.5
which the total supply flow amount of the mixture gas is maintained approximately
constant without a large variance, the supply flow amount of the monomer gas increases,
and the total supply flow amount of the reactive gas decreases simultaneously. By doing
this, a more flexible thin film can be produced.
Also, like in this example, in order to form a flexible silicon oxide thin film
having a high gas impermeability, it is preferable that the supply flow amount ratio of the
monomer gas with respect to the reactive gas be 100 or greater in the end. It is more
preferable if it is 1000 or greater. Furthermore, it is preferable if the flow amount of the
reactive gas in the mixture gas is zero. Also, in such a case, it is preferable that the time
necessary for the second thin film forming step be in a range of 1 to 3 seconds.
The thin film forming method explained above includes a first thin film forming
step for plasmatizing the mixture gas while the supply flow amount ratio varies
continuously such that the supply flow amount ratio is included in at least the specific
range. Therefore, it is possible to form a thin film having a desirable gas impermeability
easily while avoiding variation in surface quality on the produced thin film, in comparison
with a method in which the supply flow amount ratio is controlled strictly such that a thin
film has a desirable gas impermeability, and the mixture gas is plasmatized, while the
supply flow amount ratio is maintained strictly. In addition, it is possible to form a thin
film having not only gas impermeability but also flexibility, in the above second thin film
forming step, after this first thin film forming step.
Also, even if a thin film is formed on a large number of the cylindrical containers
21, it is possible to form a thin film having a high gas impermeability stably while
avoiding variations in surface quality among the containers, particularly by using the thin
film forming device 10 which is shown in the drawings and which can supply high
frequency power from a high frequency power supply section 30 to a plurality of thin film
forming chambers 20. In addition, the thin film forming device 10 can be a compact
structure. Therefore, the thin film forming device 10 is preferable in view of having low
facility cost.
Five slits 23b, each of which has a 0.5 mm width, are formed in the width
direction of the gas generating port 23 a. Here, as shown in the drawings, the gas
generation port 23a is formed on the tip of the ground electrode 23 in the thin film forming
device 10. However, there are not limitations for the number of the slits, the width of the
slits, and the interval between the slits. Furthermore, there is no limitation for the shape.
That is, an oval shape, etc., is acceptable. However, the pressure difference between the
inside and an outside of the ground electrode 23 increases if the gas generating port 23a is
formed by slits each of which has a 0.5 mm width or narrower, or if the gas generating
port 23c is formed by at least a hole 23c having a 0.5 mm or smaller diameter as shown in
FIG. 6. In these cases, the mixture gas is plasmatized in a limited manner. As a result,
the thickness of the thin film is not different between the vicinity section near the gas
generating port 23a on an inner surface of the cylindrical container 21, and the rest of the
section. Thus, the thin film is formed uniformly.
Also, it is preferable that an average surface roughness (Ra) of the outer surface
of the ground electrode 23 be in a range of 5 to 50 µm. That is, when a mixture gas is
generated in the gas generating port 23a formed in the ground electrode 23 and the
mixture gas is plasmatized, a thin film is formed not only on the inner surface of the
cylindrical container 21, but also the outer surface of the ground electrode 23. Here, if
the average surface roughness (Ra) of the outer surface of the ground electrode 23 is
roughened in a range of 5 to 50 µm contact between the thin film and the outer surface
increases, even if the thin film is formed on this outer surface. Also, there is a repetition
of expansion and contraction on the ground electrode 23 due to heat. As a result, there is
an effect that stress is reduced even if stress is applied to the thin film. . Therefore, it is
possible to restrict contamination in the cylindrical container 21 due to peeling off of the
silicon oxide thin film from the outer surface of the ground electrode 23 while using the
thin film forming device 10. Here, if the average surface roughness is 5 µm or lower, the
roughness is insufficient. Therefore, it is not possible to restrict the peeling of the thin
film desirably. On the other hand, an abnormal electric discharge may sometimes occur
in a region having an excessive roughness over 50 µm. In such a case, a thin film cannot
be formed stably.
Also, even if the outer surface of the ground electrode 23 is roughened in this
manner, it is necessary to remove the thin film formed on the ground electrode 23
periodically if the thin film has a certain degree of thickness. Therefore, it is more
preferable that, a detachable cover pipe 26 of which the outer surface has 5 to 50 µm of
average surface roughness (Ra) be disposed on the outer periphery of the ground electrode
23, as shown in FIG. 7, in order to replace a currently-disposed cover pipe 26 by a new
cover pipe 26 when the outer surface of the currently-disposed cover pipe 26 has a certain
degree of thickness of the thin film. By doing this, it is possible to continue the operation
of the thin film forming device because the cover pipe 26 can be replaced by a new cover
pipe simply and quickly, even if a certain degree of thickness of the thin film is formed on
the outer surface of the cover pipe 26. Therefore, there is a superior maintenance ability.
There is no limitation for the method of regulating the average surface roughness
in the above range. For example, it is possible to name a sand blast method or a
chemical etching method. Alternatively, it is possible to control the average surface
roughness by spraying the metal or ceramics on the outer surface of the ground electrode
23, or on the outer surface of the cover pipe 26. The surface of the sprayed material
made of metal or ceramics is not only roughened but also porous thereinside. Therefore,
the sprayed material has superior contact to with respect to the thin film. Thus, it is
possible to prevent the thin film from being removed, or peeling from the outer surface of
the ground electrode 23, and the outer surface of the cover pipe 26..
Also, in the thin film forming chamber in the thin film forming device 10, as
shown in FIG. 8, a cylindrical insulative spacer 27 may be disposed detachably between
the cylindrical container 21 and the high frequency electrode 22, while the cylindrical
container 21 is disposed inside of the high frequency electrode 22. By doing this, it is
possible to form a thin film on various cylindrical containers 21 having various sizes and
outer shapes.
That is, if a thin film is formed on the surface of a cylindrical container 21 having
a small diameter, a relatively thick cylindrical spacer 27 is used. As a result, the volume
of the space between the cylindrical container 21 and the high frequency electrode 22 is
reduced; thus, it is possible to evacuate the space in the thin film forming chamber 20
quickly. Also, even if the spacer 27 is used, the cylindrical container 21 is positioned
coaxially with the high frequency electrode 22; therefore, the thickness of the produced
thin film is uniform. Also, if the cross section of the cylindrical container 21 has a
non-circular shape, such as an oval or a rectangular shape, it is possible to form a thin film
having a desirable gas impermeability with a uniform thickness on any type of the
cylindrical containers 21 by using the spacer 27 of which the cross section of the inner
surface has an outer shape which is similar to the cylindrical container 21.
Also, in such a case, it is possible to form a thin film on the inner surface of the
cylindrical container 21 efficiently by disposing the spacer 27 so as to contact the inner
surface of the high frequency electrode 22.
Furthermore, as explained above, it is possible to form a thin film stably on
various cylindrical containers 21 having different sizes and different outer shapes by using
the spacer 27. Also, it is possible to restrict contamination in the mixture gas on an inner
surface of the high frequency electrode 22. If the inner surface of the high frequency
electrode 22 is contaminated, the electricity discharge efficiency may sometimes
decreases. Therefore, it is possible to prevent the electricity discharge efficiency from
decreasing by using the spacer 27 in this manner. Thus, the surface quality of the thin
film is stable for a long time.
It is possible to name plastics and ceramics as the material for forming the spacer
27 because they do not affect the electricity discharge efficiency in the high frequency
electrode 22, even if its inner surface is contaminated. In particular, it is possible to
name plastics because of their formability.
As explained above, the thin film forming method includes the first thin film
forming step in which the mixture gas is plasmatized while the supply flow amount ratio
varies continuously, such that the supply flow amount ratio is included in at least the
specific range. Therefore, in comparison with a method in which the supply flow
amount ratio is strictly controlled in a range, it is possible to easily form a thin film having
a desirable gas impermeability without an uneven surface quality of the thin film. Also,
it is unlikely that variations in surface quality will occur when the thin films are formed on
a large number of the substrates. Furthermore, in the above second thin film forming
step, it is possible to form a thin film having not only gas impermeability but also
flexibility after the first thin film forming step.
Also, as shown in the drawings, a certain type of the thin film forming device 10,
which can supply high frequency power from a high frequency power supply section 30 to
a plurality of thin film forming chambers 20, may be used. By doing this, even if the thin
film is formed on a large number of substrates, it is possible to form a thin film which has
a high gas impermeability, more stably and productively, without variations in surface
quality among the containers. In addition, the thin film forming device 10 has a compact
structure. Therefore, the thin film forming device 10 is preferable in view of a low
facility costs.
In the above explained thin film forming method, the plastic cylindrical container
21 is shown as an example of the substrate. There is no limitation for the material for
forming the substrate. Glass is acceptable as the material for forming the substrate as
long as a thin film, which can realize predetermined functions stably, can be formed
thereon. Also, in view of the shape, the substrate is not limited to a container.
In addition, although the above explanations are made for the case in which the
mixture gas includes the monomer gas and the reactive gas, the mixture gas may include
an inert gas such as helium, argon, etc. Also, regarding the monomer gas which is used
for forming the thin film which is formed of silicon oxide, it is possible to select it from
among hexamethyldisiloxane, 1,1,3,3-tetramethyldisiloxane, vinyltrimethylsilane,
methyltrimethoxysilane, hexamethyldisilane, methylsilane, dimethylsilane,
trimethylsilane, diethylsilane, propylsilane, phenylsilane, vinyltriethoxysilane, vinyl
trimethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, methyl
triethoxysilane, and octamethylcyclotetrasiloxane. In particular, 1,1,3,3-
tetramethyldisiloxane, hexamethyldisiloxane, and octamethylcyclotetrasiloxane are
preferable. However, it is also possible to use aminosilane and silazane.
Also, it is possible to form an alumina thin film by using an organic metal
aluminum such as trimethylaluminum as a monomer gas.
Also, it is possible to use not only oxygen but also nitrous oxide, carbon dioxide,
and ozone, as the oxidizing reactive gas.
(Experimental Example)
Hereinafter, the present invention is explained specifically in detail with respect
to Experimental Examples.
(Experimental Example 1)
A cylindrical container 21, which is made of polyethyleneterephthalate and has a
circular cross section and a 500 ml capacity, is disposed in a thin film forming chamber
20. The space in the thin film forming chamber 20 is evacuated (initial pressure for
forming a thin film: 10 Pa). After that, the flow amount of hexamethyldisiloxane
(monomer gas) and the flow amount of oxygen (reactive gas) are controlled by a
mass-flow controller. The monomer gas and the reactive gas are supplied from the base
end of the ground electrode 23 (gas introducing pipe). The initial supply flow amount of
hexamethyldisiloxane is 10 ml/min. The initial supply flow amount of oxygen is 500
ml/min (that is, the initial supply flow amount ratio = 0.02). Also, as shown in FIG. 3,
the ground electrode 23, which has the gas generating port 23a at the tip section of the
ground electrode 23, and consists of five approximately rectangular slits 23b with a 0.5
mm width, is prepared. Also, as shown in FIG. 7, the copper cover pipe 26 having an
average surface roughness (Ra) of 10 µm, which is finished by a sand-blast treatment, is
disposed on the outer periphery of the ground electrode 23.
Next, 13.56 MHz high frequency power is supplied to the high frequency
electrode 22 in the thin film forming chamber 20 for 5 seconds, by supplying 400 watts of
electricity. By doing this, a thin film is formed. During this period, the supply flow
amount ratio of hexamethyldisiloxane with respect to an oxygen varies continuously as
shown in TABLE 1.
As a result, a silicon oxide thin film is formed uniformly on the inner surface of
the cylindrical container 21. Furthermore, the above operation is repeated. Thus, the
thin film is formed on 30 cylindrical containers 21 in total. The permeability of the
oxygen is measured in each of these containers 21; thus, its average value and its standard
deviation are calculated. As a result, as shown in TABLE 2, it is clarified that it is
possible to form a thin film in which every average value and every standard deviation of
the permeability of oxygen are small, the oxygen impermeability is high, and the surface
quality does not vary. Here, the oxygen permeability is measured by Mocon Inc.'s
Oxitran 10/50. Here, in the space inside of the cylindrical container 21, the temperature
is 25°C in a 90% nitrogen/hydrogen mixture gas atmosphere. The outside space of the
cylindrical container is 25°C temperature in a 65% atmospheric condition.
In addition, although the thin film is formed by the above method thousands of
times, the produced thin film never peels off from the outer surface of the cover pipe 26.
(Experimental Examples 2 to 10)
A silicon oxide thin film is formed on an inner surface of the cylindrical container
21 in a manner similar to that of Experimental Example 1, except that the initial supply
flow amount of hexamethyldisiloxane (monomer gas) and the initial supply flow amount
of oxygen (reactive gas) are set as shown in TABLE 1, and the supply flow amount ratio
varies in accordance with TABLE 1. Furthermore, the above operation is repeated in
each of the Experimental Examples. Thus, the thin film is formed on 30 cylindrical
containers 21 in total. The permeability of the oxygen is measured in each of these
containers 21; thus, its average value and its standard deviation are calculated. As a
result, as shown in TABLE 2, it is clarified that it is possible to form a thin film in which
every average value and every standard deviation of the permeability of oxygen are small,
an oxygen impermeability is high, and the surface quality does not vary.
Also, the internal pressure in the containers 21, which are used in the
Experimental Examples 5 and 9, is maintained at 7 kg/cm2 for 2 hours, and after that the
oxygen permeability is measured in order to evaluate the flexibility of the thin film formed
on the cylindrical containers 21. As a result, the oxygen permeabilities are 0.028
fmol/s-Pa and 0.023 fmol/sPa, respectively. In the Experimental Example 9, in which
the second thin film forming step is conducted after the first thin film forming step, the
oxygen permeability does not vary before and after the space inside of the cylindrical
container 21 is pressurized. The oxygen permeability increases slightly in Experimental
Example 5 in which the second thin film forming step is omitted. This is because the
produced thin film has a sufficient flexibility because of the second thin film forming step.
By doing this, cracks are not generated because the thin film adjustably varies its shape
even if the cylindrical container 21 is deformed slightly; thus, the oxygen impermeability
is maintained desirably.
(Experimental Example 11)
As shown in FIG. 1, thin films are produced on four sets of polyethylene
terephthalate'cylindrical containers 21 simultaneously, which have circular cross sections.
In order to do this, four sets of thin film forming chambers 20, and thin film forming
device 10, which is provided with the high frequency power supply section 30 for
supplying high frequency power to each high frequency electrode 22, are used. In each
of the thin film forming chambers 20, the same ground electrode 23 as used in
Experimental Example 1 is used.
The initial supply flow amount of hexamethyldisiloxane as the monomer gas is
10 ml/min in each of the thin film forming chambers 20. The initial supply flow amount
of oxygen as the reactive gas is 500 ml/min in each of the thin film forming chambers 20
(that is, the initial supply flow amount ratio = 0.02). After that, the supply flow amount
ratio of the hexamethyldisiloxane with respect to the oxygen varies as shown in TABLE 1.
Also, the initial pressure for forming a thin film is 10 Pa. The supplied high
frequency power (charged electricity) is 400 watts in each of the thin film forming
chambers 20 (1600 watts in total). A thin film is formed by supplying 13.56 MHz of
high frequency power for 5 seconds. Here, the matching value varies during supply of
the high frequency power. Also, the reflected power is controlled so as to be at 160 watts
constantly, which is 10% or lower of the supplied electricity.
In addition, the above operation is repeated. The thin film is formed on 30
cylindrical containers 21 in total; thus, the thin film is formed on 120 cylindrical
containers 21 in the thin film forming device 10 in total. Furthermore, the permeability
of the oxygen is measured in each of these containers 21; thus, its average value and its
standard deviation are calculated. As a result, as shown in TABLE 2, it is evident that it
is possible to form a thin film in which every average value and every standard deviation
of the permeability of oxygen are small, the oxygen impermeability is high, and the
surface quality does not vary.
(Comparative Examples 1 to 8)
A thin film is formed in a manner similar to that of Experimental Example 1
except that the supply flow amount ratio is constant as shown in TABLE 1. The oxygen
impermeability is measured in the 30 produced cylindrical containers 21 in total. The
results are shown in TABLE 1 similar to Experimental Example 1.
As clearly shown in TABLES 1 and 2, it is possible to form thin films having a
desirable oxygen impermeability on many containers without variation in surface quality
in the embodiments, in which the thin films are formed by the first thin film forming step
for generating a plasma while decreasing the supply flow amount ratio of the monomer
gas with respect to the reactive gas. In particular, it is found that in the embodiment in
which the second thin film forming step is conducted after the first thin film forming step,
the produced thin film has flexibility.
On the other hand, it is possible to form a thin film having a desirable gas
impermeability in some of the comparative examples, in which the supply flow amount
ratio of the monomer gas with respect to the reactive gas is controlled constantly.
However, in many cases, a thin film having a desirable gas impermeability cannot be
formed, and the surface quality of the produced thin films vary greatly.
A second embodiment of the present invention is explained as follows.

FIG 9 is a general view showing an example of the thin film forming device
according to the present invention. As a general structure, this thin film forming device
includes a thin film forming chamber 111 in which a mixture gas including an
organosilicon compound gas and an oxidizing gas is plasmatized so as to form a silicon
oxide thin film (SiOx membrane) on a substrate, an optical spectrometer 112 (measuring
section) for measuring the intensity of hydrogen alpha rays radiated from a plasma in the
thin film forming chamber 111 and measuring an intensity of an oxygen radiation rays, an
optical fiber 114 for transmitting radiation rays separated from a glass viewport 113
disposed in the thin film forming chamber 111 toward the optical spectrometer 112, a
monitoring computer 115 for monitoring the intensity of hydrogen alpha rays measured by
the optical spectrometer 112 and for monitoring the intensity of the oxygen radiation rays,
gas supply sections 116, 117 for supplying the organosilicon compound gas and the
oxidizing gas to the thin film forming chamber 111, a vacuum pump 118 for evacuating
the space in the thin film forming chamber 111, a pressure meter 119 for measuring the
pressure in the thin film forming chamber 111, and a high frequency power supply 120 for
supplying the high frequency power to the thin film forming chamber 111.
(Thin Film Forming Chamber)
As shown in FIG. 10, the thin film forming chamber 111 includes; an outer
electrode 124 having a cylinder section 122 for containing a plastic container 121
(substrate), through which radiation can be transmitted, and a lid section 123 detachably
disposed on the upper end surface of the cylinder section 122; an insulative plate 126,
formed on the bottom end surface of the cylinder section 122, and having a supporting
hole for supporting a port section of the container 121; a bottom section 128, disposed on
the bottom end of the cylinder section 122 for covering the insulative plate 126, and
having an exhausting port 127 on the bottom surface; a gas introducing pipe 129, of which
the tip is introduced inside of the container 121 from outside of the thin film forming
chamber 111 through a hole on a side surface of the bottom section 128 and a supporting
hole 125 formed in the insulative plate 126; and a glass viewport 113, which is disposed
on a side wall of the cylinder section 122, connecting to a tip section 130 of the optical
fiber 114.
Here, the outer electrode 124 is connected to the high frequency power supply
120. The cylinder section 122 and the lid section 123, which form the outer electrode
124, are formed by a conductive member for supplying high frequency power from the
high frequency power supply 120.
Also, the gas introducing pipe 129 introduces an organosilicon compound gas and
an oxidizing gas into the container 121. In addition, the gas introducing pipe 129 is
formed by a conductive member so as to serve as a ground electrode, when it is connected
to ground.
Also, the pressure meter 119 is connected to the bottom section 128; thus, it is
possible to measure the pressure in the thin film forming chamber 111.
(Measuring Section)
The optical spectrometer 112 includes: a first bandpass filter for separating only a
specific wavelength range of radiation rays from either one of two sets of divided
radiation rays, which are separated from the viewport 113 and transmitted to the optical
spectrometer 112 through the optical fiber 114; a second bandpass filter for separating
only the remainder of the specific wavelength range of the two sets of divided radiation
rats; a first optical sensor for receiving radiation rays which pass through the first
bandpass filter; and a second optical sensor for receiving radiation rays which pass
through the second bandpass filter.
Here, in order to transmit only the wavelength (656 nm) of the hydrogen alpha
rays and radiation rays which are close to this wavelength, the permeability of the
radiation rays having a wavelength range outside of 656 ± 5 nm is 1% or lower in the first
bandpass filter.
Here, in order to transmit only this wavelength (777 nm) of the oxygen radiation
rays and radiation rays which are close to the wavelength, the permeability of the radiation
rays having a wavelength range outside of 777 ± 5 nm is 1 % or lower in the second
bandpass filter.
It is possible to use a commonly-known photoelectric element such as a photo
diode or a photo transistor for the optical sensor.
(Storing Section, Determining Section)
As shown in FIG. 11," as a general structure, the monitoring computer 115
includes a storing section 131 (storing section), a calculating section 132 (determining
section), and a determining section 133 (determining section).
Here, the storing section 131 stores average values (or a center value) of the
intensity of the hydrogen alpha rays and the intensity of the oxygen radiation rays as
standard values, with respect to a previous thin film forming process in which the
production process for the thin film was the same as that of the present thin film forming
process, and in which the inspection results were successful (that is, an organosilicon thin
film had a desirable surface quality). Also, the storing section 131 stores ranges of the
intensity of the hydrogen alpha rays and the intensity of the oxygen radiation rays, which
enable a silicon oxide thin film having a desirable surface quality to be obtained. These
ranges represent a tolerable range (threshold) for the deviation of these intensity values
from the standard values. Here, the storing section 131 may be a volatile memory such
as a RAM (Random Access Memory), a hard disk device, an optical magnetic disc device,
and a flash memory. Also, the storing section 131 may consist of a combination of these
volatile memory devices..
- The calculating section 132 calculates differences between the intensity of
hydrogen alpha rays measured by the optical spectrometer 122 in the currently-operated
thin film forming process and the standard value of the hydrogen alpha rays stored in the
storing section 131, and between the intensity of the oxygen radiation rays measured by
the optical spectrometer 112 and the standard value of the oxygen radiation rays stored in
the storing section 131.
The determining section 133 determines whether or not the difference between
these intensities and the standard values are in the tolerable ranges which are stored in the
storing section 131.
The above-explained monitoring computer 115 may consist of a memory and a
central processing unit (CPU). In order to execute the above functions, programs may be
loaded into the memory. Also, the above-explained functions may be executed by
hardware which is designed and produced for a specific use.
Also, peripherals, including an inputting device 134 such as a display touch
panel, a switch panel, and a keyboard, and a peripheral apparatus, including an outputting
device 135 such as a CRT monitor, a liquid display device, and a printer, may be
connected to the monitoring computer 115.
The inputting device 134 stores standard values and tolerable ranges in the
storing section 131 such that the standard values and the tolerable ranges are determined
in accordance with the intensity of hydrogen alpha rays and the intensity of oxygen
radiation rays, with respect to a previous thin film forming process in which the silicon
oxide thin film having a desirable surface quality was produced.
For example, the outputting device 135 outputs: the intensity of the hydrogen
alpha rays and the intensity of the oxygen radiation rays, which are measured by the
optical spectrometer 112; the standard value of the hydrogen alpha rays and the standard
value of the oxygen radiation rays which are stored iri the storing section 131; the tolerable
range of the intensity of the hydrogen alpha rays and the tolerable range of the oxygen
radiation rays, which are stored in the storing section 131; and a determination result in
the determining section 133, etc.

Next, a thin film forming process and a monitoring method therefor are explained
with reference to FIGS. 9 to 11.
Before starting the thin film forming process, average values (or a center value)
for a quantity (intensity) of the hydrogen alpha rays and a quantity (intensity) of the
oxygen radiation rays are inputted into the inputting device 134, and the inputted average
values are stored in the storing section 131 in the monitoring computer 115 as standard
values, such that the average values are based on a previous thin film forming process in
which the silicon oxide thin film had a desirable surface quality in the same thin film
forming process as the present thin film forming process. The tolerable range of each of
the quantities of the radiation rays, which are determined based on records for the quantity
(intensity) of the hydrogen alpha rays and the quantity (intensity) of the oxygen radiation
rays, are inputted into the inputting device 34. The inputted tolerable ranges are stored in
the storing section 131 in the monitoring computer 115, such that the quantities of the
radiation rays are in accordance with a previous thin film forming process, in which the
produced organosilicon thin film had a desirable surface quality.
The lid section 123 of the thin film forming chamber 111 is removed. The
container 121 through which the radiation rays can be transmitted is put into the cylinder
section 122 such that the gas introducing pipe 129 can be inserted into the container 121.
The port section of the container 121 is engaged by the supporting hole 125 of the
insulative plate 126 so as to be supported there. After that, the lid section 123 is attached
onto thean upper end surface of the cylinder section 122.
Next, the vacuum pump 118 is started so as to depressurize the space in the thin
film forming chamber 111 by exhausting the gas in the external electrode 124 from the
exhausting port 127 through the insulative plate 126; thus, the pressure in the space in the
thin film forming chamber 111 was a predetermined value (approximately a vacuum
condition). After that, a gas which includes an organosilicon compound gas and an
oxidizing gas is supplied from the gas supplying sections 116 and 117 to the thin film
forming chamber 111. A mixture gas which includes the organosilicon compound gas
and the oxidizing gas is introduced into the container 121 through the gas introducing pipe
129. •
Next, the mixture gas is plasmatized between the external electrode 124 and the
gas introducing pipe 129 serving as a ground electrode by starting the high frequency
power supply 120 and supplying the high frequency power to the external electrode 124 in
the thin film forming chamber 111. Thus, the organosilicon thin film is formed on the
inner surface of the container 121.
During the thin film forming process, radiation rays which are radiated from a
plasma 140 (inside the dotted line in the drawing) generated in the container 121 and
which permeate through the transparent container 121 are separated from the viewport 113
so as to be transmitted to the optical spectrometer through the optical fiber 114. After the
radiation rays which are transmitted to the optical spectrometer 112 are divided into two
sets of rays, one of the sets of divided radiation rays are transmitted through the first
bandpass filter. The hydrogen alpha rays which are transmitted there are received by the
first optical sensor for measurement of the quantity (intensity) of the hydrogen alpha rays.
Also, the other set of the two divided radiation rays are transmitted through the second
bandpass filter. The oxygen radiation rays which are transmitted therethrough are
received by the second optical sensor for measurement of the quantity (intensity) of the
oxygen radiation rays.
The quantity (intensity) of the hydrogen alpha rays and the quantity (intensity) of
the oxygen radiation rays which are measured by the optical spectrometer 112 are
converted into voltages in accordance with the measured quantities; thus, the converted
quantities are outputted to the monitoring computer 115.
The quantities of the radiation rays which are outputted to the monitoring
computer 115 are treated as follows.
First, in the calculating section 132, the difference between the quantity
(intensity) of hydrogen alpha rays measured by the optical spectrometer 122 and the
standard value of the hydrogen alpha rays stored in the storing section 131 is calculated.
Also, the difference between the quantity (intensity) of the oxygen radiation rays
measured by the optical spectrometer 12 and the standard value of the oxygen radiation
rays stored in the storing section 131 is calculated.
Next, the determining section 133 determines whether or not the differences
between these quantities and the standard values are within the tolerable ranges which are
stored in the storing section 131.
The determination result in the determining section 133 is outputted to the
outputting device 133 together with the quantity (intensity) of the hydrogen alpha rays and
the quantity (intensity) of the oxygen radiation rays which are measured by the optical
spectrometer 112, the standard value of the hydrogen alpha rays and the standard value of
the oxygen radiation rays which are stored in the storing section 131, and the tolerable
range of the intensity of the hydrogen alpha rays and the tolerable range of the oxygen
radiation rays which are stored in the storing section 131. Also, if the differences
between the quantities of the radiation ray and the standard values for the radiation rays
exceed the tolerable ranges which are stored in the storing section 131 as a result of the
determination made in the determining section 133, an abnormality in the radiation rays
which are emitted from the plasma may be reported to an operator by activating an alarm
device and lamps, etc.
As organosilicon compounds which are used in the thin film forming process, it is
possible to name, for example, tetramethyldisiloxane, hexamethyldisiloxane,
vinyltrimethylsilane, methyltrimethoxysilane, hexamethyldisilane, methylsilane,
dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane,
vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane,
phenyltrimethoxysilade, methyl triethoxysilane, octamethylcyclotetrasiloxane, etc..
As the oxidizing gas, it is possible to name, for example, oxygen, carbon
monoxide, carbon dioxide, and ozone, etc. Also, it is possible to mix argon or helium as
a carrier gas into the organosilicon compound gas or the oxidizing gas.
In the above-explained monitoring method for the thin film forming process, the
intensity of the hydrogen alpha rays and the intensity of the oxygen radiation rays which
are radiated from the plasma during the thin film forming process are measured, and the
measured intensities are compared with the intensity of the hydrogen alpha rays and the
intensity of the oxygen radiation rays under the condition that a silicon oxide thin film
which has a desirable surface quality is obtained. Therefore, it is possible to know
reliably whether or not the process has been properly carried out (whether or not the
plasma structure is normal). Also, it is possible to determine whether or not the produced
thin film has a desirable surface quality during the process.
That is, if the mixture gas consisting of an organosilicon compound gas and an
oxidizing gas is plasmatized, radiation rays having unique properties are radiated because
various excited specimen exist in the plasma. These radiation rays include not only
hydrogen alpha rays and oxygen radiation rays but also hydrogen beta rays, SiO2
radiation, and CH3 radiation. However, when the quantity (intensity) of the radiation
rays emitted from the plasma generated in the container 121 is measured, the emitted
radiation rays transmitted on a path from the container 121, through the container 121, the
relatively small glass viewport 113, and the optical fiber 114 to the the optical
spectrometer 112, into which the emitted radiation is finally introduced. The intensity of
the emitted radiation is attenuated in the path. Therefore, if the intensities of the excited
specimen, such as hydrogen beta rays, hydrogen gamma rays, SiO radiation, and CH3
radiation, etc., having low intensities initially, are measured, measurement error increases
undesirably. Therefore, it is possible to know reliably whether or not the structure of the
plasma is normal by monitoring the intensity of hydrogen alpha rays, oxygen radiation
rays, having relatively high intensities.
Also, the intensity of the two sets of radiation rays such as the hydrogen alpha
rays and oxygen radiation rays are measured. Thus, it is possible to reliably detect an
abnormality in various parameters (thin film forming pressure, supplied electricity, flow
amounts of organosilicon compound gas and oxidizing gas) in the thin film forming
process. That is, if an abnormality occurs in at least one of the parameters, the
abnormality is indicated in at least the intensity of the hydrogen alpha rays or the intensity
of the oxygen radiation rays. Therefore, it is possible to detect an abnormality of the
process reliably.
Also, it is possible to detect an abnormality in the process more reliably by the
thin film forming process monitoring method according to the present invention and by
monitoring a process condition (for example, parameters such as degree of vacuum,
supplied power, flow amount of an introduced gas).
Also, the above-explained thin film forming device includes: an optical
spectrometer 121 for measuring the intensity of hydrogen alpha rays radiated from a
plasma in the thin film forming chamber 111 and the intensity of the oxygen radiation
rays; and a determining section 133, in which the intensity of the hydrogen alpha rays
measured in the optical spectrometer 121 and the intensity of the hydrogen alpha rays
stored in the storing section 131 are compared, the intensity of the oxygen radiation rays
measured by the optical spectrometer 121 and the intensity of the oxygen radiation rays
stored in the storing section 131 are compared, and whether or not the measured intensity
of the hydrogen alpha rays and the measured intensity of the oxygen radiation rays are
within tolerable ranges. Therefore, it is possible to know reliably whether or not the
process is working properly and whether or not the structure of the plasma is normal.
Also, it is possible to determine whether or not the produced thin film has a desirable
surface quality during the process.
Also, the thin film forming device according to the present invention is not
limited to the structure shown in the drawings. Thus, the thin film forming device may
include: a chamber for plasmatizing a mixture gas consisting of an organosilicon
compound gas and an oxidizing gas, and for forming a silicon oxide thin film on the
surface of a substrate; a measuring section for measuring the intensity of hydrogen alpha
rays and the intensity of an oxygen radiation rays, which are radiated from the plasma
generated in the chamber; a storage section for storing the intensity of the hydrogen alpha
rays and the intensity of the oxygen radiation rays such that the organosilicon thin film has
a desirable surface quality which is measured in a previous thin film forming process; and
a determining section for comparing the intensity of the hydrogen alpha rays measured by
the measuring section with the intensity of the hydrogen alpha rays stored in the storage
section, comparing the intensity of the oxygen radiation rays measured by the measuring
section with the intensity of the oxygen radiation rays stored in the storage section, and
determining whether or not the intensity of the measured hydrogen alpha rays and the
intensity of the measured oxygen radiation rays are within a specific range.
For example, the measuring section is not limited to the optical spectrometer 121
which is shown in the drawings. Any measuring section is acceptable as long as it is
possible to measure the intensity of hydrogen alpha rays and the intensity of oxygen
radiation rays. However, if a bandpass filter for separating only a specific wavelength
range of radiation rays from among the radiation rays radiated from the plasma in the thin
film forming chamber is used, it is possible to simplify the measuring section at a low
cost; therefore, the measuring section should preferably include a bandpass filter.
Also, any bandpass filter is acceptable as long as it is possible to extract hydrogen
alpha rays or oxygen radiation rays from among the radiation rays which are radiated from
the plasma.
Also, in the drawings, the plasma 140 is observed through the viewport 113 while
traversing horizontally. However, it is acceptable if the viewport 113 is disposed on the
lid section 123 so as to observe the plasma 140 from above. Also, it is acceptable if the
viewport 113 is disposed diagonally in the cylinder section 122 so as to observe the
plasma 140 diagonally downward from above. In order to separate the radiation rays
radiated from the plasma in a longitudinal cylindrical container, it is preferable to observe
the plasma diagonally downward from above because the quantity (intensity) of the
radiation is high.
Also, the determining section (determining section 133) in the monitoring
computer 115 in the drawing calculates a difference between the intensities of the
measured hydrogen alpha rays and the measured oxygen radiation rays and the standard
values of the radiation rays stored in the storing section 131 (calculating section 132) and
determines whether or not the difference between these intensities and the standard values
are within the tolerable ranges stored in the storing section 131 (determining section 133)
However, in the present invention, the determining section is not limited to such a
structure. For example, the storing section 131 may store an upper limit value and a
lower limit value for the intensity of the hydrogen alpha rays and the intensity of oxygen
radiation rays, and the determining section may determine whether or not the intensity of
the measured hydrogen alpha rays and the intensity of the measured oxygen radiation rays
are in a range between the upper limit value and the lower limit value, without calculating
a difference between the intensity of the radiation rays and the standard value, such that
the stored intensities for the hydrogen alpha rays and the oxygen radiation rays are
determined in accordance with a previous thin film forming process in which the
production process for the thin film was the same as that of the present thin film forming
process.
Also, in the case in which the standard value of the hydrogen alpha rays and the
standard value of the oxygen radiation rays which are stored in the storing section 131
fluctuate in the process while the intensity of the radiation fluctuates throughout the
process, the standard value of the radiation may be stored in the storing section 131 over
time in the process; thus, a tolerable range for the standard value may be set over time in
the process. The process, in terms of several phases, can be divided into a beginning
phase, a middle phase, and an approximate end phase.
Also, it is not necessary to use the monitoring computer 115 in the thin film
forming process monitoring method according to the present invention. That is, it is
acceptable if the intensity of the measured hydrogen alpha rays and the intensity of the
oxygen radiation rays are outputted from the optical spectrometer 121 directly to an
outputting device such as a monitor, and an operator monitors the outputted result and
compares the intensity of these radiation rays to the measured intensity of the hydrogen
alpha rays and the measured intensity of the oxygen radiation rays under the condition that
the silicon oxide thin film which has a desirable surface quality is obtained; thus, it is
determined whether or not the silicon oxide thin film which has a desirable surface quality
is formed.
Also, the thin film forming process monitoring method according to the present
invention is not limited to the thin film forming process in which high frequency waves
are used. The thin film forming process monitoring method according to the present
invention can be adapted to a thin film forming process in which microwaves are used.
Also, the substrate on which the thin film is formed in the present invention is not
limited to a plastic container 121 through which radiation rays can" be transmitted as
shown in the drawings. The present invention can be adapted to various substrates such
as a container, a film, and a sheet which are made of plastic, glass, or metal.
Examples
Examples of the present invention are shown below.
A silicon oxide thin film is formed on the inner surface of the container 21 which
has a 500 ml capacity and is made of polyethyleneterephthalate by using the thin film
forming device as shown in FIGS. 9 to 11. A mixture gas which includes
hexamethyldisiloxane (hereinafter HMDSO) and oxygen is used as the process gas.
(Measurement of Standard Value)
The space in the thin film forming chamber 111 is depressurized by starting the
vacuum pump 118 so as to have a predetermined thin film forming pressure (100 Pa).
After that, the HMDSO and oxygen are supplied from the gas supplying sections 116,117
to the thin film forming chamber 111. The mixture gas is introduced into the container
121 through the gas introducing pipe 129. Here, the flow amount of the HMDSO is 2
seem; The flow amount of oxygen is 100 seem.
Next, the mixture gas is plasmatized between the outer electrode 124 and the gas
introducing pipe 129 serving as a ground electrode by starting the high frequency power
supply 120 and supplying the 13.56 MHz high frequency waves to the outer electrode 124
in the thin film forming chamber 111 at 200 watts for 10 seconds; thus, the silicon oxide
thin film is formed on an inner surface of the container 121.
Radiation rays which are radiated from the plasma 140 which is generated in the
container 121 and permeated through the transparent container 121 are separated from the
glass viewport 113 of which the diameter is 10 mm during the thin film forming process
so as to be transmitted to the optical spectrometer 112 through the optical fiber 114 which
has a 6 mm diameter and a 2 m length. After the radiation rays which are transmitted to
the optical spectrometer 112 are divided into two sets of rays, one sets of the divided
radiation rays is transmitted through the first bandpass filter of which the central
wavelength is 656 nm. The hydrogen alpha rays which are transmitted there are received
by the first optical sensor for measurement of a quantity (intensity) of the hydrogen alpha
rays. Also, the other set of the two divided radiation rays is transmitted through the
second bandpass filter of which the central wavelength is 777 nm. The oxygen radiation
rays which are transmitted there are received by the second optical sensor for
measurement of a quantity (intensity) of the oxygen radiation rays. A voltage in a range
of 0 to 5 V is outputted from an optical sensor.
Also, the permeability of the oxygen in the container 121 on which a thin film is
formed is measured in accordance with a Mocon method so as to evaluate a surface
quality (oxygen impermeability) of the produced thin film. More specifically, the oxygen
permeability is measured by using Mocon Inc.'s Oxitran 10/50. Here, the space inside of
the cylindrical container 121 is under conditions of a 25 °C and a 90% nitrogen/hydrogen
mixture gas atmosphere, and the outside space of the container 121 is at a 25°C and 65%
atmospheric condition.
TABLES 3 to 6 show various parameters (conditions) for the process such as the
quantity of the measured hydrogen alpha rays, a quantity of the oxygen radiation rays, and
the oxygen impermeability of the container 121 on which a thin film is formed.
It is found that the oxygen impermeability of the container 121 on which a thin
film is formed is sufficiently low; thus, the container 121 has a desirable surface quality of
the thin film. In addition, the thin film forming processes are repeated under the same
condition. As a result, it is found that it is possible to form a thin film which has a
desirable surface quality (oxygen impermeability) if the quantity of the hydrogen alpha
rays are in a range of 3.0 to 3.4 V and the quantity of the oxygen radiation rays is in a
range of 3.0 to 3.4 V. Therefore, the standard value is 3.2 and the tolerable range is ± 2 V
for the quantity of hydrogen alpha rays and oxygen radiation rays.
(Variance of Quantity due to Fluctuation of Flow Amount of HMDSO)
Next, the variance of the quantity of hydrogen alpha rays, the variance of the
quantity of oxygen radiation rays, and the variance of the surface quality of a thin film are
observed under condition that the flow amount of HMDSO fluctuates from 2 (seem) to 1,
5, and 10 (seem). Results are shown in TABLE 3.
The quantity of the obtained hydrogen alpha rays and the quantity of the obtained
oxygen radiation rays indicate a fluctuation of the flow amount of HMDSO; thus, it is
possible to estimate oxygen impermeability to some degree, which is one of the indexes
for indicating the surface quality based on the quantity of each radiation.
Next, the variance of the quantity of hydrogen alpha rays, the variance of the
quantity of oxygen radiation rays, and the variance of the surface quality of a thin film are
observed under condition that the flow amount of oxygen fluctuates from 100 (seem) to 50
and 200 (seem). The results are shown in TABLE 4.
The quantity of the obtained hydrogen alpha rays and the quantity of the obtained
oxygen radiation rays indicate a fluctuation of the flow amount of oxygen; thus, it is
possible to estimate oxygen impermeability to some degree, which is one of the indexes
for indicating the surface quality based on the quantity of each radiation.
(Variance of Quantity of Radiation due to Fluctuation of Applied Power)
Next, the variance of the quantity of hydrogen alpha rays, the variance of the
quantity of oxygen radiation rays, and the variance of the surface quality of a thin film are
observed under the condition that the applied power fluctuates from 200 (watts), 100, and
300 (watts). The results are shown in TABLE 5.
The quantity of the fluctuated hydrogen alpha rays and the quantity of the
fluctuated oxygen radiation rays indicate a fluctuation of the thin film forming pressure;
thus, it is possible to estimate the oxygen impermeability to some degree, which is one of
the indexes for indicating the surface quality based on the quantity of each radiation.
(Variance of Quantity of Radiation due to Fluctuation of Thin Film Forming Pressure)
Next, the variance of the quantity of hydrogen alpha rays, the variance of the
quantity of oxygen radiation rays, and the variance of the surface quality of a thin film are
observed under the condition that the thin film forming pressure fluctuates from 10 (Pa) to
20 and 50 (Pa) by varying the operation conditions of the vacuum pump 118. The results
are shown in TABLE 6.
The quantity of the obtained hydrogen alpha rays and the quantity of the obtained
oxygen radiation rays indicate a fluctuation of the thin film forming pressure; thus, it is
possible to estimate oxygen impermeability to some degree, which is one of the indexes
for indicating the surface quality based on the quantity of each radiation.
INDUSTRIAL APPLICABILITY
As explained above, such a thin film forming method includes a first thin film
forming step in which the supply flow amount ratio is included within a specific range.
Therefore, it is possible to form a thin film easily which has a desirable gas
impermeability without variation in comparison with a method in which the supply flow
amount ratio is strictly controlled in a range such that a thin film which has a desirable gas
impermeability can be formed and plasmatization is performed while such a supply flow
amount ratio is strictly maintained. Furthermore, by performing a second thin film
forming step after this first thin film forming step, it is possible to form a thin film which
has not only gas impermeability but also flexibility.
Also, according to the thin film forming device according to the present
invention, it is possible to supply high frequency power from a high frequency power
supply to a plurality of thin film forming chambers. Therefore, it is possible to strictly
form a thin film which has a certain quality without variation for various substrates.
Also, the facility cost is inexpensive and the facility size is compact.
Also, according to the thin film forming process monitoring method according to
the present invention, the intensity of hydrogen alpha rays and the intensity of oxygen
radiation rays are measured during the process. In addition, these intensities are
compared to the intensity of hydrogen alpha rays and the intensity of oxygen radiation
rays which are realized under previous condition in which an organosilicon thin film
which has a desirable surface quality was obtained. Thus, it is possible to know the
structure of the generated plasma more accurately and determine whether or not the
surface quality of the produced thin film has a desirable condition during the process.
Also, if a specific wavelength range of radiation rays is separated from among the
radiation rays which are radiated from the plasma; it is possible to measure the intensity of
the radiation by an inexpensive and simple measuring device.
Also, since the thin film forming device according to the present invention has
the above structure, it is possible to know the structure of the generated plasma more
accurately and determine whether or not the generated thin film has a desirable quality
during the process.
Also, if a bandpass filter is used which separates only a specific wavelength range
of radiation rays from among the radiation rays which are radiated from the plasma in the
thin film forming chamber, it is possible to simplify the measuring section at a low cost.
According to the present invention, in a thin film forming process which uses a
plasma CVD method in which a silicon oxide thin film is formed on the surface of a
substrate by plasmatizing a mixture gas which includes an organosilicon compound gas
and an oxidizing gas, it is possible to know the structure of the generated plasma more
accurately and determine whether or not the produced thin film has a desirable surface
quality during the process.
We Claim:
1. A thin film forming method for plasmatizing a mixture gas, the mixture
gas consisting of a monomer gas, such as hereinbefore described, and an
oxidizing reactive gas, such as hereinbefore described, and for forming a thin
film on a surface of a substrate, the thin film being made of an oxide,
comprising:
a first step of forming a first thin film by plasmatizing the mixture gas
while, varying a flow amount ratio of the monomer gas with respect to the
reactive gas under the condition that the flow amount ratio is 0.05 or lower
within 2 to 5 seconds; and
the flow amount of monomer gas is gradually reduced while the amount
of the oxidizing reactive gas is maintained at the substantially fixed level.
2. A thin film forming method as claimed in Claim 1, wherein the flow
amount ratio decreases continuously in the first thin film forming step.
3. A thin film forming method as claimed in Claim 2, wherein an initial
value of the flow amount ratio in the first thin film forming step is in a range of
0.02 to 0.2.
4. A thin film forming method as claimed in Claim 2 or 3, comprising:
a second step of forming the thin film by increasing the flow amount
ratio after the first thin film forming step.
5. A thin film forming method as claimed in any one of Claims 1 to 4,
wherein the mixture gas is plasmatized by controlling reflected power to be
10% or lower than supplied high frequency power, the reflected power being
generated by supplying high frequency power of 100 MHz or lower to a high
frequency electrode through an impedance matching network.
6. A thin film forming device for plasmatizing a mixture gas, the mixture
gas consisting of a monomer gas and an oxidizing reactive gas, and for forming
a thin film, on an inner surface of a cylindrical container having a closed end,
the thin film being made of an oxide, comprising:
a plurality of thin film forming chambers, each of the thin film forming
chambers being provided with a cylindrical high frequency electrode, one end
of the high frequency electrode being closed such that the cylindrical container
can be disposed on an inner surface of the high frequency electrode, and a
ground electrode disposed in the cylindrical container, the ground electrode
having a gas generating port on a tip section of the ground electrode such that
the gas generating port generates the mixture gas;
a high frequency power supply section having an impedance matching
network and a high frequency power supply such that high frequency power
can be supplied to the high frequency electrode through the impedance
matching network; and
a flow amount control section for controlling a flow amount ratio of the
monomer gas and the reactive gas contained in the mixture gas so that the flow
amount ratio is 0.05 or lower within 2 to 5 seconds, wherein
the high frequency power is supplied to a plurality of the thin film
forming chambers from the high frequency power supply section, and
the flow amount of monomer gas is gradually reduced while the amount
of the oxidizing reactive gas is maintained at a substantially fixed level.
7. A thin film forming device as claimed in Claim 6, wherein a detachable
spacer which is formed by an insulative member is disposed between the
cylindrical container and the high frequency electrode.
8. A thin film forming device as claimed in Claim 6 or 7, wherein the gas
generating port has at least a hole of which the diameter is 0.5 mm or smaller
and/or a slit of which the width is 0.5 mm or narrower.
9. A thin film forming device as claimed in any one of Claims 6 to 8,
wherein an average surface roughness of an outer surface of the ground
electrode is 5 to 50 µm.
10. A thin film forming device as claimed in any one of Claims 6 to 8,
wherein a detachable cover pipe is provided on at least a part of an outer
periphery of the ground electrode, and an average surface roughness of an outer
surface of the cover pipe is 5 to 50 µm.
11. A thin film forming device as claimed in Claim 9 or 10, wherein a metal
member or a ceramic member is sprayed onto the outer surface which has the
average surface roughness.
12. A thin film forming process monitoring method for plasmatizing a
mixture gas, the mixture gas consisting of an organosilicon compound gas and
an oxidizing gas, such as hereinbefore described, and for forming a silicon
oxide thin film on a surface of a substrate, comprising:
measuring an intensity of hydrogen alpha rays radiated from the plasma
and an intensity of oxygen radiation rays;
comparing the intensity of the hydrogen alpha rays and the intensity of
the oxygen radiation rays, with an already measured intensity of hydrogen alpha
rays and an already measured intensity of the oxygen radiation rays, for which
the silicon oxide thin film has a desirable surface quality; and
determining whether or not the silicon oxide thin film having a desirable
surface quality is formed.
13. A thin film forming process monitoring method as claimed in Claim 12,
wherein the intensity of the hydrogen alpha rays and the intensity of the oxygen
radiation rays are measured by extracting radiation rays which have a specific
range of wavelengths from among radiation rays which are radiated from the
plasma, and measuring the intensity thereof.
14. A thin film forming process monitoring method as claimed in Claim 12,
wherein the intensity of the hydrogen alpha rays and the intensity of the oxygen
radiation rays are measured by measuring an intensity of radiation rays which
have 656±5 nm wavelength range and an intensity of radiation rays which have
777± 5 nm wavelength range among the radiation rays which are radiated from
the plasma.
15. A thin film forming device, comprising:
a chamber for plasmatizing a mixture gas, the mixture gas consisting of
an organosilicon compound gas and an oxidizing gas, and for forming a silicon
oxide thin film on a surface of a substrate;
a measuring section for measuring intensity of hydrogen alpha rays and
an intensity of oxygen radiation rays, both kinds of rays being radiated from the
plasma in the chamber;
a storage section for storing the intensity of the hydrogen alpha rays and
the intensity of the oxygen radiation rays such that the organosilicon thin film
has a predetermined desirable surface quality; and
a determining section for determining whether or not the intensity of the
measured hydrogen alpha rays and the intensity of the measured oxygen
radiation rays are within specific ranges by comparing the intensity of the
measured hydrogen alpha rays with the intensity of the hydrogen alpha rays in
the storage section, and by comparing the intensity of the oxygen radiation rays
measured by the measuring section with the intensity of the oxygen radiation
rays which is stored in the storage section.
16. A thin film forming device as claimed in Claim 15, wherein the
measuring section is provided with a bandpass filter for separating only
radiation rays having a specific wavelength range from among the rays which
are radiated from the plasma in the chamber.
17. A thin film forming device as claimed in Claim 15, wherein the
measuring section comprises:
a first bandpass filter of which a transmittance for the radiation rays
which have a wavelength range outside 656 ± 5 nm is 1% or lower;
a second bandpass filter of which a transmittance for the radiation rays
which have a wavelength range outside 777 ± 5 nm is 1% or lower;
a first photosensor which receives the radiation rays which pass through
the first bandpass filter; and
a second photosensor which receives the radiation rays which pass
through the second bandpass filter,

In a thin film forming method in which a mixture gas which includes a monomer
gas and an oxidizing reactive gas is plasmatized and a thin film which is formed of an
oxide is formed on a surface of a substrate, the mixture gas is plasmatized while a flow
amount ratio of the monomer gas with respect to the reactive gas is varied under the
condition that the flow amount ratio is included within at least a specific range. In this
case, a thin film forming device 10 in which high frequency electricity is supplied from a
high frequency power supply section 30 to a plurality of thin film forming chambers is
used. By doing this, it is possible to provide a thin film forming method and a thin film
forming device in which it is possible to strictly form a thin film which has characteristics
such as a gas barrier property without variation in quality and to provide flexibility to the
thin film even if the thin film is formed onto a large number of substrates. Also, in a
monitoring method for measuring the intensity of the hydrogen alpha rays and the
intensity of the oxygen radiation rays which are radiated from the plasma while forming
the thin film and comparing each intensity with a standard intensity of each radiation
under the condition that the thin film has a desirable surface quality, and for determining
whether or not a thin film which has a desirable surface quality is formed, a thin film
forming device is provided with: an optical spectrometer which measures the intensity
of each radiation, a storage section which stores a standard intensity of each radiation, and
a determining section which determines whether or not each measured intensity is in a
specific range by comparing each measured intensity with the standard intensity of each
radiation. By doing this, it is possible to determine whether or not the produced thin film
has a desirable surface quality during the process.