U.S. patent application number 14/925498 was filed with the patent office on 2016-02-18 for apparatus for forming metal oxide film, method for forming metal oxide film, and metal oxide film.
This patent application is currently assigned to TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION. The applicant listed for this patent is KYOTO UNIVERSITY, TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION. Invention is credited to Shizuo FUJITA, Toshiyuki KAWAHARAMURA, Hiroyuki ORITA, Takahiro SHIRAHATA, Akio YOSHIDA.
Application Number | 20160047049 14/925498 |
Document ID | / |
Family ID | 45066286 |
Filed Date | 2016-02-18 |
United States Patent
Application |
20160047049 |
Kind Code |
A1 |
SHIRAHATA; Takahiro ; et
al. |
February 18, 2016 |
APPARATUS FOR FORMING METAL OXIDE FILM, METHOD FOR FORMING METAL
OXIDE FILM, AND METAL OXIDE FILM
Abstract
A method for forming a metal oxide film, the method including:
forming a source solution containing metal into a mist, heating a
substrate, supplying the source solution formed into a mist onto a
first main surface of the substrate through a first supply path,
and supplying hydrogen peroxide through a second path different
from the first supply path onto the first main surface of the
substrate, where the method further includes, in the following
order, preliminarily preparing data showing a relationship among a
molar ratio of an amount of the hydrogen peroxide to an amount of
the zinc in the source solution, a carrier concentration of the
metal oxide film, and a mobility of the metal oxide film,
determining an amount of the hydrogen peroxide supplied with the
data, and supplying the determined amount of the hydrogen peroxide
through the second path onto the first main surface of the
substrate.
Inventors: |
SHIRAHATA; Takahiro; (Tokyo,
JP) ; ORITA; Hiroyuki; (Tokyo, JP) ; YOSHIDA;
Akio; (Tokyo, JP) ; FUJITA; Shizuo; (Kyoto,
JP) ; KAWAHARAMURA; Toshiyuki; (Kochi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION
KYOTO UNIVERSITY |
Tokyo
Kyoto |
|
JP
JP |
|
|
Assignee: |
TOSHIBA MITSUBISHI-ELECTRIC
INDUSTRIAL SYSTEMS CORPORATION
Tokyo
JP
KYOTO UNIVERSITY
Kyoto
JP
|
Family ID: |
45066286 |
Appl. No.: |
14/925498 |
Filed: |
October 28, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13643380 |
Oct 25, 2012 |
|
|
|
PCT/JP10/59243 |
Jun 1, 2010 |
|
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|
14925498 |
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Current U.S.
Class: |
427/600 |
Current CPC
Class: |
C23C 18/1287 20130101;
C23C 18/1216 20130101; C23C 18/1279 20130101; C23C 18/1291
20130101; C23C 16/407 20130101 |
International
Class: |
C23C 18/12 20060101
C23C018/12 |
Claims
1. A method for forming a metal oxide film, the method comprising:
forming a source solution comprising metal into a mist; heating a
substrate; supplying the source solution formed into a mist onto a
first main surface of the substrate in the heating, through a first
supply path; and supplying hydrogen peroxide through a second path
different from the first supply path onto the first main surface of
the substrate in the heating, wherein the method further comprises,
in the following order: preliminarily preparing data showing a
relationship among a molar ratio of an amount of the hydrogen
peroxide to an amount of the zinc in the source solution, a carrier
concentration of the metal oxide film, and a mobility of the metal
oxide film; determining an amount of the hydrogen peroxide supplied
with the data, and supplying the determined amount of the hydrogen
peroxide through the second path onto the first main surface of the
substrate, wherein the substrate is arranged under atmospheric
pressure, the source solution is converted into a mist by an
ultrasonic atomizer, and the metal is zinc.
2-3. (canceled)
4. The method according to claim 1, wherein the source solution
further comprises ammonia.
5. The method according to claim 1, wherein the source solution
further comprises ethylenediamine.
6. The method according to claim 1, further comprising supplying
ozone onto the first main surface of the substrate in the
heating.
7. The method according to claim 2, wherein the supplying of the
source solution and the supplying of hydrogen peroxide do not
comprise supplying ozone onto the first main surface of the
substrate in the heating, and the molar ratio is 20 or smaller.
8. The method according to claim 1, wherein the supplying of the
hydrogen peroxide further comprises supplying a dopant of a
predetermined conductivity type onto the first main surface of the
substrate with the hydrogen peroxide through the second path.
9. The method of claim 1, wherein the source solution comprises
boron, nitrogen, fluorine, aluminum, phosphorus, gallium, arsenic,
niobium, indium, antimony, bismuth, vanadium, tantalum, or any
combination thereof.
10. The method of claim 1, wherein the source solution comprises
water, an alcohol, or a mixed solution thereof.
Description
CROSS REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. application Ser.
No. 13/643,380, filed on Oct. 25, 2012, which is a 35 U.S.C. 371
national stage patent application of international patent
application PCT/JP10/059243, filed on Jun. 1, 2010, the entire
content of which is incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to an apparatus for forming a
metal oxide film that forms a metal oxide film on a substrate, and
a method for forming a metal oxide film. Further, the present
invention relates to a metal oxide film formed by the method for
forming a metal oxide film.
BACKGROUND ART
[0003] In the fields of solar cells, light emitting devices, touch
panels, sensors, and the like, metal oxide films are formed on
substrates. Conventionally, Patent Documents 1, 2, and 3 disclose
the technique of forming a metal oxide film on a substrate.
[0004] In the technique of Patent Document 1, a metal oxide film is
formed on a substrate by bringing a solution in which a metal salt
or a metal complex is dissolved into contact with a heated
substrate. In this technique, the solution contains at least one of
an oxidizing agent and a reducing agent.
[0005] In the technique of Patent Document 2, a tetrabutyltin
solution or a tin tetrachloride solution, in which hydrogen
peroxide is added as an oxidizing agent, is sprayed onto a
preheated substrate and thermally decomposed. Then, after the
substrate temperature lowered by spraying of the solution returns,
the solution is sprayed repeatedly. Accordingly, a thin film of tin
oxide is grown on the surface of the substrate.
[0006] In the technique of Patent Document 3, a solution in which a
thin film material is dissolved in a volatile solvent is
intermittently sprayed toward a substrate kept hot from above to
form a transparent conductive film on the surface of the substrate.
In this technique, intermittent spraying is high-speed pulsed
intermittent spraying in which one spraying duration is 100
milliseconds or less.
PRIOR ART DOCUMENTS
Patent Documents
[0007] Patent Document 1: Japanese Patent Application Laid-Open No.
2007-109406
[0008] Patent Document 2: Japanese Patent Application Laid-Open No.
2002-146536
[0009] Patent Document 3: Japanese Patent Application Laid-Open No.
2007-144297
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0010] If a material having high reactivity is selected in forming
a meal oxide film on a substrate, the material reacts with oxygen
and moisture in the atmosphere and is decomposed. Meanwhile, if a
material stable in the atmosphere is selected, as to the
temperature for forming a metal oxide film, a substrate needs to be
heated at high temperature. Under present circumstances, there is
desired a technique of heating a temperature at lower temperature,
to thereby form a metal oxide film having low resistance on a
substrate.
[0011] Therefore, an object of the present invention is to provide
an apparatus for forming a metal oxide film that forms a metal
oxide film having low resistance through a low temperature
treatment, and a method for forming a metal oxide film. Further,
the present invention provides a metal oxide film formed by the
method for forming a metal oxide film.
MEANS TO SOLVE THE PROBLEM
[0012] In order to solve the above-mentioned problem, an apparatus
for forming a metal oxide film according to the present invention
includes: a first container storing a source solution containing
metal; a second container storing hydrogen peroxide; a reaction
chamber in which a substrate is disposed, including a heating unit
heating the substrate; a first path connecting the first container
and the reaction chamber, for supplying the source solution from
the first container to the reaction chamber; and a second path
connecting the second container and the reaction chamber, for
supplying the hydrogen peroxide from the second container to the
reaction chamber.
[0013] Further, a method for forming a metal oxide film according
to the present invention includes the steps of: (A) forming a
source solution containing metal into a mist; (B) heating a
substrate; (C) supplying the source solution formed into a mist in
the step (A) onto a first main surface of the substrate in the step
(B); and (D) supplying hydrogen peroxide through another path
different from a supply path for the source solution onto the first
main surface of the substrate in the step (B).
EFFECTS OF THE INVENTION
[0014] In the present invention, a heated substrate is supplied
with a source solution containing metal and is also supplied with
hydrogen peroxide through a channel different from that for the
source solution. This enables to form a metal oxide film having low
resistance on a first main surface of a substrate even if the
substrate is heated at low temperature.
[0015] The object, features, aspects, and advantages of the present
invention will be more apparent from the following detailed
description in conjunction with the attached drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a view showing a schematic configuration of an
apparatus 100 for forming a metal oxide film according to a first
embodiment.
[0017] FIG. 2 is a view for describing a method of producing a
solution 11 in which an amount of hydrogen peroxide is
adjusted.
[0018] FIG. 3 is a figure showing the relationships among the
carrier concentration of a metal oxide film, mobility of the metal
oxide film, and molar ratio of H.sub.2O.sub.2/Zn.
[0019] FIG. 4 is a view showing a schematic configuration of an
apparatus 150 for forming a metal oxide film according to a third
embodiment.
[0020] FIG. 5 is a view showing a schematic configuration of an
apparatus 200 for forming a metal oxide film according to a fourth
embodiment.
[0021] FIG. 6 is a view showing a schematic configuration of an
apparatus 250 for forming a metal oxide film according to the
fourth embodiment.
[0022] FIG. 7 is a view showing a schematic configuration of an
apparatus 500 for forming a metal oxide film, which causes a source
solution to contain hydrogen peroxide and a metal source and
supplies the source solution to a substrate.
[0023] FIG. 8 is a figure showing experimental results (sheet
resistance--molar ratio) in which the apparatus 500 for forming a
metal oxide film was used.
[0024] FIG. 9 is a figure showing experimental results (film
thickness--molar ratio) in which the apparatus 500 for forming a
metal oxide film was used.
[0025] FIG. 10 is a figure showing experimental results (sheet
resistance--heating temperature) in which the apparatus 150 for
forming a metal oxide film was used.
[0026] FIG. 11 is a figure showing experimental results (sheet
resistance--molar ratio) in which the apparatus 150 for forming a
metal oxide film was used.
[0027] FIG. 12 is another figure showing experimental results
(sheet resistance--molar ratio) in which the apparatus 150 for
forming a metal oxide film was used.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0028] Hereinafter, the present invention is specifically described
with reference to the drawings showing embodiments thereof.
First Embodiment
[0029] FIG. 1 is a view showing a schematic configuration of an
apparatus 100 for forming a metal oxide film according to a first
embodiment.
[0030] As shown in FIG. 1, the apparatus 100 for forming a metal
oxide film according to the first embodiment is configured of a
reaction chamber 1, a heating unit 3, a first solution container
5A, a second solution container 5B, a first mist forming unit 6A, a
second mist forming unit 6B, a first path L1, and a second path
L2.
[0031] In the film forming apparatus 100, a spray pyrolysis method,
a pyrosol method, a mist deposition method, or the like is
performed. That is, in the film forming apparatus 100, a
predetermined solution formed into a mist is sprayed onto a first
main surface of a substrate 2, so that a predetermined metal oxide
film can be formed on the first main surface of the substrate
2.
[0032] The substrate 2 being a film-formed body, on which a metal
oxide film is formed, is provided in the reaction chamber 1. The
heating unit 3 is disposed in the reaction chamber 1, and the
substrate 2 is placed on the heating unit 3 (alternatively, the
substrate 2 is provided apart from the heating unit 3 in the
reaction chamber 1 so as to face the heating unit 3). A metal oxide
film is formed on the first main surface of the substrate 2 being
heated by the heating unit 3.
[0033] As is apparent from this description, the first main surface
of the substrate 2 which is referred to in the present
specification is the main surface of the substrate 2 on a side on
which the metal oxide film is formed. On the other hand, a second
main surface of the substrate 2 which is referred to in the present
specification is the main surface of the substrate 2 on a side
being in contact with the heating unit 3.
[0034] During the film forming treatment for a metal oxide film,
the reaction chamber 1 is in a non-vacuum (that is, at atmospheric
pressure).
[0035] A glass substrate, a resin substrate, a film, and the like
used in the fields of solar cells, light-emitting devices, touch
panels, and flat panel displays such as liquid crystal panels can
be employed for the substrate 2.
[0036] A heater or the like can be employed for the heating unit 3,
which can heat the substrate 2 placed on the heating unit 3 (or
facing the heating unit 3). The heating temperature of the heating
unit 3 is adjusted by an external controller (not shown) included
in the film forming apparatus 100, so that the heating unit 3 is
heated to a metal oxide film forming temperature during the film
forming treatment.
[0037] Stored in the first solution container 5A is a source
solution 10 containing metal. The first mist forming unit 6A is
provided onto the bottom of the first solution container 5A. For
example, an ultrasonic atomizer can be employed for the first mist
forming unit 6A. The first mist forming unit 6A can form the source
solution 10 in the first solution container 5A into a mist.
[0038] While the configuration in which each mist forming unit is
disposed on the bottom of each solution container is described
herein, the place in which each mist forming unit is provided is
not necessarily limited to the bottom of each solution
container.
[0039] The source solution 10 contains an alkoxide compound, a
.beta.-diketone compound, an organic salt compound, an inorganic
salt compound, or the like as a metallic element containing
compound.
[0040] The metal source contained in the source solution 10 may be
appropriately selected in accordance with the use of a metal oxide
film formed. For example, titanium (Ti), zinc (Zn), indium (In),
tin (Sn), or the like can be employed as the metal source.
[0041] The source solution 10 is not necessarily required to
contain a dopant source. However, it is preferable that the source
solution 10 contain at least any one of boron (B), nitrogen (N),
fluorine (F), aluminum (Al), phosphorus (P), gallium (Ga), arsenic
(As), niobium (Nb), indium (In), antimony (Sb), bismuth (Bi),
vanadium (V), and tantalum (Ta) as the dopant source.
[0042] Water, alcohols such as ethanol and methanol, and mixed
solutions thereof can be employed for the solvent of the source
solution 10.
[0043] As shown in FIG. 1, the first solution container 5A and the
reaction chamber 1 are connected to each other via the first path
L1. The source solution 10 formed into a mist by the first mist
forming unit 6A is supplied from the first solution container 5A to
the reaction chamber 1 through the first path L1. The supplied
source solution 10 is splayed onto the first main surface of the
substrate 2 disposed being heated in the reaction chamber 1.
[0044] Meanwhile, stored in the second solution container 5B is a
solution 11 containing hydrogen peroxide. The second mist forming
unit 6B is provided onto the bottom of the second solution
container 5B. For example, an ultrasonic atomizer can be employed
for the second mist forming unit 6B. The second mist forming unit
6B can form the solution 11 in the second solution container 5B
into a mist.
[0045] Water, alcohols such as ethanol and methanol, and mixed
solutions thereof can be employed for the solvent of the solution
11.
[0046] The description has been given of the mode in which the
source solution 10 in the first solution container 5A contains a
predetermined dopant. In place of the source solution 10 containing
the dopant, the solution 11 in the second solution container 5B may
contain the dopant.
[0047] As shown in FIG. 1, the second solution container 5B and the
reaction chamber 1 are connected to each other via the second path
L2. As is apparent from FIG. 1, the second path L2 is a path
provided independently of the first path L1. The solution 11 formed
into a mist by the second mist forming unit 6B is supplied from the
second solution container 5B to the reaction chamber 1 through the
second path L2. The supplied solution 11 is splayed onto the first
main surface of the substrate 2 being heated in the reaction
chamber 1.
[0048] As described above, the first path L1 and the second path L2
are paths independently of each other. Accordingly, the source
solution 10 containing metal and the solution 11 containing
hydrogen peroxide are supplied to the reaction chamber 1 through
different systems. Then, the source solution 10 and the solution 11
are mixed together in the reaction chamber 1.
[0049] The source solution 10 and the solution 11 supplied to the
reaction chamber 1 react with each other on the substrate 2 being
heated, whereby a predetermined metal oxide film is formed on the
first main surface of the substrate 2. The metal oxide film formed
is a transparent conductive film of indium oxide, zinc oxide, tin
oxide, or the like, which depend on the type of the metal source
contained in the source solution 11.
[0050] The source solution 10 and solution 11 unreacted in the
reaction chamber 1 are always (continuously) discharged out of the
reaction chamber 1.
[0051] Further, as shown in FIG. 2, the film forming apparatus 100
includes a container 51 and a container 52 separately. The
container 51 stores hydrogen peroxide 11a. Meanwhile, the container
52 stores a component 11b other than the hydrogen peroxide 11a of
the solution 11.
[0052] The film forming apparatus 100 is externally operated for
producing the solution 11. This operation is aimed for adjusting
and determining the content of the hydrogen peroxide 11a in the
solution 11. The operation is executed on the film forming
apparatus 100, so that a predetermined amount of the hydrogen
peroxide 11a is delivered from the container 51 and another
predetermined amount of the component 11b is delivered from the
container 52. Accordingly, the hydrogen peroxide 11a and the
component 11b each output are supplied to the second solution
container 5B, and the solution 11 containing the hydrogen peroxide
11a of a content determined through the above-mentioned operation
is produced in the second solution container 5B.
[0053] Next, the method for forming a metal oxide film according to
the present embodiment is described.
[0054] First, the hydrogen peroxide 11a and the component 11b are
mixed together, to thereby produce the solution 11. Here, the
source solution 10 containing a predetermined molar amount of zinc
as a metal source is prepared in the first solution container
5A.
[0055] The film forming apparatus 100 is provided with an input
part (not shown) for inputting/selecting the content of hydrogen
peroxide in the solution 11. A user performs the operation of
inputting or selecting a desired value as the content of hydrogen
peroxide on the input part. Then, a first amount of the hydrogen
peroxide 11a according to the operation is delivered from the
container 51. Meanwhile, a second amount of the component 11b
according to the operation is delivered from the container 52.
Then, the hydrogen peroxide 11a and the component 11b each
delivered are supplied to the second solution container 5B, whereby
the solution 11 is produced in the second solution container 5B.
Here, the content of hydrogen peroxide in the produced solution 11
is a desired value in the operation.
[0056] The inventors have found that the relationships shown in
FIG. 3 exist among the molar ratio (=H.sub.2O.sub.2/Zn) of the
content of hydrogen peroxide in the solution 11 (amount of hydrogen
peroxide supplied to the reaction chamber 1) to the amount of zinc
contained in the source solution 10, the carrier concentration of
the metal oxide film formed, and the mobility of the metal oxide
film formed.
[0057] The vertical axis on the left side in FIG. 3 represents the
carrier concentration (cm.sup.-3) of the metal oxide film formed.
The vertical axis on the right side in FIG. 3 represents the
mobility (cm.sup.2/Vs) of the metal oxide film formed. The
horizontal axis in FIG. 3 represents the molar ratio
(=H.sub.2O.sub.2/Zn) of amount of substance of hydrogen peroxide
(H.sub.2O.sub.2) to amount of substance of zinc (Zn). "Square
marks" in FIG. 3 indicate data values showing the relationship
between the molar ratio and the carrier concentration. "Triangular
marks" in FIG. 3 indicate data values showing the relationship
between the molar ratio and the mobility.
[0058] FIG. 3 reveals that the carrier concentration of the metal
oxide film formed decreases along with an increase of the content
of hydrogen peroxide in the solution 11 to the content of zinc in
the source solution 10. Further, FIG. 3 reveals that the mobility
of the metal oxide film formed increases along with an increase of
the content of hydrogen peroxide in the solution 11 to the content
of zinc in the source solution 10.
[0059] As is well known, the resistivity of a metal oxide film
formed is proportional to the inverse of carrier
concentration.times.mobility.
[0060] Therefore, data shown in FIG. 3 is prepared in advance prior
to the production of the solution 11. Then, the user considers that
the physical properties (such as transmittance) of the metal oxide
film are changed by changing the resistivity, mobility and carrier
concentration of a metal oxide film formed. In the case of the
operation of selecting/inputting the content of hydrogen peroxide,
the user takes the above into consideration and then determines the
content of hydrogen peroxide in the solution 11 in accordance with
the use of the metal oxide film formed, using the data shown in
FIG. 3. In other words, the user determines the amount of hydrogen
peroxide supplied to the reaction chamber 1 using the data shown in
FIG. 3.
[0061] The source solution 10 is prepared in the first container
5A, and the solution 11 is prepared in the second container 5B, so
that the source solution 10 is formed into a mist by the first mist
forming unit 6A in the first solution container 5A, and the
solution 11 is formed into a mist by the second mist forming unit
6B in the second solution container 5B.
[0062] The source solution 10 formed into a mist is supplied to the
reaction chamber 1 through the first path L1. Meanwhile, the
solution 11 formed into a mist is supplied to the reaction chamber
1 through the second path L2 that is a path different from the
first path L1.
[0063] Meanwhile, the substrate 2 being in contact with the heating
unit 3 is heated to a metal oxide film forming temperature by the
heating unit 3, and the temperature of the substrate 2 is
maintained at the metal oxide film forming temperature. For
example, the temperature of the substrate 2 is maintained at
300.degree. C. or lower.
[0064] The source solution 10 formed into a mist and the solution
11 formed into a mist are supplied to the first main surface of the
substrate 2 being heated as descried above. Accordingly, a
predetermined metal oxide film is formed on the first main surface
of the substrate 2 located in the reaction chamber 1.
[0065] As described above, in the present embodiment, the source
solution 10 containing metal and the solution 11 containing
hydrogen peroxide are supplied to the reaction chamber 1 through
different paths. Then, the source solution 10 and the hydrogen
peroxide (solution 11) are brought into contact with the substrate
2 being heated in the reaction chamber 1.
[0066] Therefore, a metal oxide film having low resistivity can be
formed on the first main surface of the substrate 2 even if the
heating temperature of the substrate 2 is low. This effect is
described in a fifth embodiment below with reference to
experimental data.
[0067] In the present embodiment, the data shown in FIG. 3 is
prepared in advance, and the amount of hydrogen peroxide to the
amount of zinc contained in the source solution 10, which is
supplied to the reaction chamber 1, is determined by using the
data.
[0068] Therefore, the carrier concentration and mobility of a metal
oxide film formed can be adjusted, whereby it is possible to
provide a metal oxide film having physical property values
according to the use.
[0069] As described above, the source solution 10 or the solution
11 may contain a dopant. Depending on the conductivity type of a
dopant, a metal oxide film (transparent conductive film) being an
n-type semiconductor can enter an electron-richer state. In this
case, the electric resistance of a metal oxide film (transparent
conductive film) formed can be lowered more. Further, it is
conceivable that a metal oxide film may be a p-type semiconductor
depending on the conductivity type of the dopant. In the metal
oxide film being a p-type semiconductor, a hole serves as a carrier
to become conductive, which increases the usefulness thereof as a
light-emitting device rather than as a transparent conductive
film.
Second Embodiment
[0070] In a second embodiment, the source solution 10 described in
the first embodiment further contains ammonia or
ethylenediamine.
[0071] That is, in the film forming apparatus 100 shown in FIG. 1,
the first solution container 5A stores the source solution 10
further containing a predetermined amount of ammonia or a
predetermined amount of ethylenediamine.
[0072] Then, the first mist forming unit 6A forms the source
solution 10 further containing ammonia or ethylenediamine into a
mist. Then, the source solution 10 formed into a mist is supplied
to the reaction chamber 1 through the first path L1. As described
also in the first embodiment, in this case, the substrate 2 is
heated to a metal oxide film forming temperature in the reaction
chamber 1.
[0073] The configuration of the film forming apparatus 100 and the
operation in the film forming method other than the above are
similar to those described in the first embodiment.
[0074] As described above, in the present embodiment, the source
solution 10 containing ammonia (or ethylenediamine) in addition to
metal is formed into a mist. Then, in the reaction chamber 1, the
source solution 10 formed into a mist is brought into contact with
the heated substrate 2.
[0075] Accordingly, it is possible to further improve the
production efficiency of the metal oxide while maintaining low
resistance of a metal oxide film formed. That is, the source
solution 10 further contains ammonia (or ethylenediamine), leading
to improvement of the film forming rate of a metal oxide film.
Through the improvement of the film forming rate, it is possible to
form a metal oxide film having a predetermined film thickness in a
short time.
Third Embodiment
[0076] FIG. 4 is a view showing a schematic configuration of an
apparatus 150 for forming a metal oxide film according to a third
embodiment.
[0077] As is apparent from the comparison between FIGS. 1 and 4,
the apparatus 150 for forming a metal oxide film according to the
present embodiment has a configuration in which an ozone generator
7 is added to the configuration of the apparatus 100 for forming a
metal oxide film according to the first embodiment. In addition, a
third path L3 is disposed in a film forming apparatus 200 for
supplying ozone from the ozone generator 7 to the second solution
container 5B.
[0078] The other configuration is similar to the descriptions above
in the first and second embodiments except that the ozone generator
7 and the third path L3 are additionally provided.
[0079] The ozone generator 7 can generate ozone. The ozone
generated in the ozone generator 7 is supplied to the second
solution container 5B through the third path L3. Then, the supplied
ozone is supplied toward the first main surface of the substrate 2
in the reaction chamber 1 through the second path L2, together with
the solution 11 containing hydrogen peroxide.
[0080] In the ozone generator 7, for example, an oxygen molecule is
decomposed by applying high voltage between parallel electrodes
disposed in parallel and passing oxygen between the electrodes, and
the oxygen molecule couples with another oxygen molecule, so that
ozone is generated.
[0081] When ozone, the misty solution 11, and the misty source
solution 10 are supplied to the reaction chamber 1, the ozone, the
solution 11, and the source solution 10 react with each other on
the substrate 2 being heated, whereby a predetermined metal oxide
film is formed on the first main surface of the substrate 2. The
ozone, solution 11, and source solution 10 unreacted in the
reaction chamber 1 are always (continuously) discharged out of the
reaction chamber 1.
[0082] Next, a method for forming a metal oxide film according to
the present embodiment is described.
[0083] First, as described in the first embodiment (see FIGS. 2 and
3), the amount of hydrogen to the content of a metal source
contained in the source solution 10, which is supplied to the
reaction chamber 1, is determined. Then, the solution 11 containing
hydrogen peroxide is produced in the second solution container 5B
based on the determined amount.
[0084] The source solution 10 and the solution 11 are prepared in
the first solution container 5A and the second solution container
5B, respectively, and then, ozone is generated in the ozone
generator 7. In the first solution container 5A, the first mist
forming unit 6A forms the source solution 10 into a mist. In the
second solution container 5B, the second mist forming unit 6B forms
the solution 11 into a mist.
[0085] The generated ozone is supplied to the second solution
container 5B through the third path L3. Then, the ozone and the
misty solution 11 are supplied to the reaction chamber 1 through
the second path L2. The misty source solution 10 is supplied to the
reaction chamber 1 through the first path L1. As described in the
first embodiment, the second path L2 through which hydrogen
peroxide passes is different from the first path L1 through which
the source solution 10 containing metal passes.
[0086] Meanwhile, the substrate 2 being in contact with the heating
unit 3 is heated to a metal oxide film forming temperature by the
heating unit 3, and the temperature of the substrate 2 is
maintained at the metal oxide film forming temperature. For
example, the temperature of the substrate 2 is maintained at
approximately 200.degree. C.
[0087] The ozone, the source solution 10 containing metal, and the
solution 11 containing hydrogen peroxide are supplied to the first
main surface of the substrate 2 being heated. The contact of the
ozone and the solutions 10 and 11 with the substrate 2 being heated
causes thermal decomposition of the ozone, which produces an oxygen
radical. The oxygen radical accelerates the decomposition of the
source solution 10, so that a predetermined metal oxide film is
formed on the first main surface of the substrate 2.
[0088] As described above, the ozone generator 7 that generates
ozone to be supplied to the reaction chamber 1 is also provided in
the present embodiment.
[0089] Therefore, ozone and active oxygen produced as a result of
the decomposition of ozone due to heat or the like are highly
reactive, and accordingly, the decomposition and oxidation of
material compound in the source solution 10 are accelerated. This
enables to form a metal oxide film having low resistance on the
substrate 2 even in a state in which a heating temperature is lower
compared with the first embodiment.
[0090] Also in the present embodiment, the source solution 10 may
contain ammonia or ethylenediamine as described in the second
embodiment. Alternatively, the source solution 10 or the solution
11 may contain a dopant as described in the first embodiment. The
metal contained in the source solution 10 is appropriately selected
depending on the type of a metal oxide film to be formed. Still
alternatively, the amount of hydrogen peroxide to the amount of
zinc contained in the solution 10, which is supplied to the
reaction chamber 1, may be determined in accordance with the use of
a metal oxide film (zinc oxide film) to be formed, as described
with reference to FIGS. 2 and 3.
Fourth Embodiment
[0091] The present embodiment describes modifications of the third
embodiment. FIGS. 5 and 6 show the modifications of the film
forming apparatus including the ozone generator 7 described in the
third embodiment.
[0092] In the apparatus 200 for forming a metal oxide film shown in
FIG. 5, the ozone generator 7 is connected to the reaction chamber
1 by means of the third path L3. The ozone generated in the ozone
generator 7 is supplied to the reaction chamber 1 through the third
path L3. As is apparent from the comparison between FIGS. 4 and 5,
in the film forming apparatus 200, the ozone passes through the
third path L3 provided independently of the first and second paths
L1 and L2.
[0093] Therefore, the source solution 10 containing metal, the
solution 11 containing hydrogen peroxide, and the ozone are
supplied to the reaction chamber 1 in which the substrate 2 being
heated is disposed through the first path L1, the second path L2,
and the third path L3, respectively.
[0094] The other configuration and operation of the film forming
apparatus 200 are similar to the description in the third
embodiment.
[0095] In an apparatus 250 for forming a metal oxide film shown in
FIG. 6, the ozone generator 7 is connected to the reaction chamber
1 by means of the third path L3. The ozone generated in the ozone
generator 7 is supplied to the reaction chamber 1 through the third
path L3. Further, a container 21 is provided. The container 21
stores a gas 18 containing hydrogen peroxide of a predetermined
concentration. The second path L2 connecting the container 21 to
the reaction chamber 1 is provided. The gas 18 in the container 21
is supplied to the reaction chamber 1 through the second path L2.
The film forming apparatus 250 is further provided with another
solution container 5D that stores a solution 19 containing a
dopant. The another solution container 5D is connected to the
reaction chamber 1 by means of another path L4. The solution 19 in
the another solution container 5D that is formed into a mist by
another mist forming unit 6D is supplied to the reaction chamber 1
through the another path L4.
[0096] That is, as is apparent from the comparison between FIGS. 4
and 6, the film forming apparatus 250 is different from the film
forming apparatus 150 in the following points.
[0097] In the film forming apparatus 250, ozone passes through the
third path L3 provided independently of the paths L1, L2, and L4.
In place of preparing liquid hydrogen peroxide (see container 21
and gas 18) and supplying the misty hydrogen peroxide to the
reaction chamber 1, in the film forming apparatus 250, gaseous
hydrogen peroxide is prepared, and the hydrogen peroxide is
supplied to the reaction chamber 1 as the gas. The film forming
apparatus 250 is also provided with the second path L2 for
supplying gaseous hydrogen peroxide independently of the first path
L1 through which the source solution 10 is supplied.
[0098] The film forming apparatus 250 is provided with the another
solution container 5D that stores the solution 19 containing a
dopant and the another path L4 for transferring the solution 19.
That is, the another solution container 5D and the another path L4
are elements dedicated to a dopant.
[0099] Therefore, in a case where the supply of a dopant to the
reaction chamber 1 is omitted, the film forming apparatus 250 may
not be provided with the elements including the another solution
container 5D and the another path L4. Also in a case where the
supply of a dopant to the reaction chamber 1 is not omitted, if the
source solution 10 contains a dopant as well, the film forming
apparatus 250 may not be provided with the elements including the
another solution container 5D and the another path L4.
[0100] In the film forming apparatus 250, the source container 10
containing metal, the gas 18 containing hydrogen peroxide, and the
ozone are supplied to the reaction chamber 1 in which the substrate
2 being heated is disposed through the first path L1, the second
path L2, and the third path L3, respectively, and the solution 19
containing a dopant is supplied thereto through the another path
L4.
[0101] The other configuration and operation of the film forming
apparatus 250 are similar to the description in the third
embodiment.
Fifth Embodiment
[0102] The present embodiment describes the experimental data
showing the effects of the present invention.
Comparative Example
[0103] First, the experimental results in a case of using a film
forming apparatus 500 shown in FIG. 7 are described before
describing the effects of the present invention.
[0104] In the film forming apparatus 500 shown in FIG. 7, a
solution container 5 stores a source solution 31. The source
solution 31 contains not only metal but also hydrogen peroxide. The
source solution 31 formed into a mist by a mist forming unit 6 is
supplied to the reaction chamber 1 through one path L. That is, in
the film forming apparatus 500, hydrogen peroxide and a metal
source of a film to be formed are supplied to the reaction chamber
1 through the same system.
[0105] The experiment of forming a zinc oxide film on the first
main surface of the substrate 2 was conducted using the film
forming apparatus 500. FIGS. 8 and 9 show the experimental
results.
[0106] In the experiment, the source solution 31 in which
ZnAcac.sub.2 (zinc acetylacetonate)=0.02 mol/L and MeOH
(methanol)/H.sub.2O (water)=9 was used, and the heating temperature
of the substrate 2 was set to approximately 300.degree. C. Further,
the source solution 31 contained hydrogen peroxide, and the content
of the hydrogen peroxide was varied in the range where
H.sub.2O.sub.2 (hydrogen peroxide)/Zn (zinc)=0 to 10 (specifically,
the content of zinc was constant, where H.sub.2O.sub.2/Zn=0, 0.1,
0.5, 1, 2, 5, 10).
[0107] FIG. 8 shows the results of the measurement of the sheet
resistance of each zinc oxide film formed on the substrate 2 by
varying the content of hydrogen peroxide in the source solution 31.
In FIG. 8, the vertical axis represents a sheet resistance
(.OMEGA./sq.) and the horizontal axis represents H.sub.2O.sub.2/Zn
(molar ratio).
[0108] As shown in FIG. 8, in the case of using the film forming
apparatus 500, the sheet resistance of a zinc oxide film formed
sharply increases along with an increase of the content of hydrogen
peroxide in the source solution 31. In the measurement where
H.sub.2O.sub.2/Zn=2, the sheet resistance of a zinc oxide film
formed exceeded the range of the vertical axis in FIG. 8 (as
described below, a zinc oxide film is not formed if
H.sub.2O.sub.2/Zn=5 or larger.
[0109] That is, as is apparent from the results of FIG. 8, in a
case of using the film forming apparatus 500 supplying hydrogen
peroxide and metal through the same system, a zinc oxide film
having low resistance could not be formed, but a zinc oxide film
having considerably high resistance was formed.
[0110] FIG. 9 shows the results of the measurement of the film
thickness of each zinc oxide film formed on the substrate 2 by
varying the content of hydrogen peroxide in the source solution 31.
In FIG. 9, the vertical axis represents a film thickness (nm) and
the horizontal axis represents H.sub.2O.sub.2/Zn (molar ratio).
Also in FIG. 9, the content of zinc was constant, whereas the
content of hydrogen peroxide was varied.
[0111] As shown in FIG. 9, in the case of using the film forming
apparatus 500, the film thickness of a zinc oxide film formed
decreases along with an increase of the content of hydrogen
peroxide in the source solution 31. In the measurements where
H.sub.2O.sub.2/Zn=5 or larger, a zinc oxide film was not formed on
the substrate 2.
Experimental Result 1
[0112] FIG. 10 is a figure showing the experimental results using
the film forming apparatus 150 described in the third embodiment
(see FIG. 4).
[0113] In "Experimental result 1", the source solution 10 contains
not only a metal source but also ammonia, a dopant, and the like.
Specific film forming conditions in "Experimental result 1" are as
follows.
[0114] That is, the source solution 10 in which ZnAcac2=0.02 mol/L,
GaAcac3=0.03 mol/L, NH.sub.3 (ammonia solution) 28%=3 mL (in 100 mL
of solution), and MeOH/H.sub.2O=9 was used. Further, the solution
11 containing hydrogen peroxide of an amount that satisfies
H.sub.2O.sub.2/Zn (content of zinc in the source solution 11)=25 in
which MeOH/H.sub.2O=9 was used. The flow rate of ozone supplied to
the reaction chamber 1 was 10 mg/min. Moreover, the heating
temperature of the substrate 2 was varied from 145.degree. C. to
287.degree. C.
[0115] FIG. 10 shows the results of the measurement of the sheet
resistance of each zinc oxide film formed on the substrate 2 by
varying the film forming temperature for the substrate 2. In FIG.
10, the vertical axis represents a sheet resistance (.OMEGA./sq.)
and the horizontal axis represents the temperature (.degree.
C.).
[0116] FIG. 10 also shows the results obtained by employing the
film forming conditions described above except that hydrogen
peroxide was not supplied (omitting the container 5B in FIG. 4).
Specifically, in FIG. 10, white triangular marks indicate the
experimental result data in the case where the hydrogen peroxide
was supplied, whereas black diamond marks indicate the experimental
result data in the case where the hydrogen peroxide was not
supplied.
[0117] As shown in FIG. 10, at the film forming temperatures except
for 287.degree. C. at which the substrate 2 was heated, the sheet
resistance of a metal oxide film formed reduced more in the case
where hydrogen peroxide was supplied. Further, in the case where
hydrogen peroxide was supplied, a metal oxide film having
sufficiently low resistance could be produced even at a low film
forming temperature (approximately 200.degree. C.).
Experimental Result 2
[0118] FIG. 11 is a figure showing the experimental results using
the film forming apparatus 150 described in the third embodiment
(see FIG. 4).
[0119] In "Experimental result 2", the source solution 10 contains
not only a metal source but also ammonia, a dopant, and the like.
Specific film forming conditions in "Experimental result 2" are as
follows.
[0120] That is, the source solution 10 in which ZnAcac2=0.04 mol/L,
GaAcac3=0.06 mol/L, NH.sub.3 (ammonia solution) 28%=3 mL (in 100 mL
of solution), and MeOH/H.sub.2O=9 was used. Further, the solution
11 containing hydrogen peroxide of an amount that satisfies
H.sub.2O.sub.2/Zn (the content of zinc in the source solution 11)=0
to 49 where MeOH/H.sub.2O=9 was used. Specifically, the content of
hydrogen peroxide in the solution 11 was varied so as to satisfy
H.sub.2O.sub.2/Zn=0, 5, 12, 15, 20, 24, 37 and 49 (content of zinc
was constant). The flow rate of ozone supplied to the reaction
chamber 1 was 10 mg/min. Moreover, the heating temperature of the
substrate 2 was approximately 200.degree. C.
[0121] FIG. 11 shows the results of the measurement of the sheet
resistance of each zinc oxide film formed on the substrate 2 by
varying the content of hydrogen peroxide in the solution 11. In
FIG. 11, the vertical axis represents a sheet resistance
(.OMEGA./sq.) and the horizontal axis represents H.sub.2O.sub.2/Zn
(molar ratio).
[0122] FIG. 11 shows the measurement results in both cases where
ozone was supplied to the reaction chamber 1 and where ozone was
not supplied to the reaction chamber 1 (the film forming conditions
were the same in both cases except for the presence/absence of the
ozone supply). In FIG. 11, white triangular marks indicate the
experimental result data in the case where ozone was supplied,
whereas black diamond marks indicate the experimental result data
in the case where ozone was not supplied.
[0123] As shown in FIG. 11, in the case where ozone was supplied, a
metal oxide film having sufficiently low resistance could be formed
at the low film forming temperature (approximately 200.degree. C.).
In the case where ozone was supplied, the resistance of a metal
oxide film formed tends to decrease along with an increase of the
amount of hydrogen peroxide in the area where H.sub.2O.sub.2/Zn
does not exceed 12. Meanwhile, in the area where H.sub.2O.sub.2/Zn
is 12 or larger, the resistance of a metal oxide film formed is
approximately constant even if the amount of hydrogen peroxide is
increased.
[0124] As shown in FIG. 11, even in a case where ozone was not
supplied, as is apparent from the comparison with FIG. 8, the sheet
resistance of a metal oxide film formed maintains a sufficiently
low resistance even when the amount of hydrogen peroxide was
increased.
[0125] As shown in FIG. 11, in a case where ozone was not supplied,
a zinc oxide film having a sheet resistance equal to or smaller
than the sheet resistance of a zinc oxide film formed in the case
where hydrogen peroxide was not contained (case where the vertical
axis in FIG. 11 is zero) could be formed in the area in which
H.sub.2O.sub.2/Zn is 20 or smaller.
Experimental Result 3
[0126] FIG. 12 is a figure showing the experimental results using
the film forming apparatus 150 described in the third embodiment
(see FIG. 4).
[0127] In "Experimental result 1" and "Experimental results 2", a
dopant of a predetermined conductivity type was contained in the
source solution 10. On the other hand, in "Experimental result 3",
the solution 11 containing hydrogen peroxide contains a dopant of a
predetermined conductivity type. Specific film forming conditions
in "Experimental result 3" are as follows.
[0128] That is, the source solution 10 in which ZnAcac2=0.04 mol/L,
NH.sub.3 (ammonia solution) 28%=3 mL (in 100 mL of solution), and
MeOH/H.sub.2O=9 was used. Further, the solution 11 containing
gallium of an amount that satisfies GaAcac3=0.0008 mol/L and
containing hydrogen peroxide of an amount that satisfies
H.sub.2O.sub.2/Zn (the content of zinc in the source solution 11)=0
to 4.9 where MeOH/H.sub.2O=9 was used. Specifically, the content of
hydrogen peroxide in the solution 11 was varied so as to satisfy
H.sub.2O.sub.2/Zn=0, 0.5, 1, 2.5, and 4.9 (the content of zinc was
constant). The flow rate of ozone supplied to the reaction chamber
1 was 10 mg/min. Moreover, the heating temperature of the substrate
2 was approximately 200.degree. C.
[0129] FIG. 12 shows the results of the measurement of the sheet
resistance of each zinc oxide film formed on the substrate 2 by
varying the content of hydrogen peroxide in the solution 11. In
FIG. 12, the vertical axis represents a sheet resistance
(.OMEGA./sq.) and the horizontal axis represents H.sub.2O.sub.2/Zn
(molar ratio).
[0130] As shown in FIG. 12, a metal oxide film having sufficiently
low resistance could be formed at a low film forming temperature
(approximately 200.degree. C.). Further, similarly to the tendency
shown in FIG. 11, the resistance of a metal oxide film formed
decreases along with an increase of the amount of hydrogen
peroxide.
[0131] In the experimental results shown in FIG. 11, if
H.sub.2O.sub.2/Zn=5, the sheet resistance of a metal oxide film
formed was 2200 (.OMEGA./sq.) in a case where ozone was supplied.
In "Experimental result 2" where the results of FIG. 11 were
obtained, the source solution 10 contained a dopant of a
predetermined conductivity type.
[0132] On the other hand, as shown in FIG. 12, the sheet resistance
of a metal oxide film formed was 630 (.OMEGA./sq.) or lower in
"Experimental Result 3" in which the solution 11 contained a dopant
of a predetermined conductivity type. That is, the sheet resistance
of a metal oxide film formed becomes smaller in the case where the
solution 11 contains a dopant compared with the case where the
source solution 10 contains a dopant.
[0133] On both of the film forming conditions for "Experimental
result 2" and the film forming conditions for "Experimental result
3", ZnAcac.sub.2=0.04 mol/L. On the other hand, Ga/Zn=0.15 on the
film forming conditions for "Experimental result 2", whereas
Ga/Zn=0.02 on the film forming conditions for "Experimental result
3". That is, it is understood that the sheet resistance of a metal
oxide film formed became smaller in "Experimental result 3"
compared with "Experimental result 2" although the amount of a
dopant decreased more in "Experimental result 3" compared with
"Experimental Result 2".
[0134] While the present invention has been described above in
detail, the foregoing description is in all aspects illustrative,
and the present invention is not limited thereto. That is, numerous
modifications and variations can be devised in the described
aspects without departing from the scope of the invention.
TABLE-US-00001 Description of Reference Symbols 1 reaction chamber
2 substrate 3 heating unit 5A first solution container 5B second
solution container 5D another solution container 6A first misting
unit 6B second misting unit 6D another misting unit 7 ozone
generator 10 source solution 11 solution 18 gas (containing
hydrogen peroxide) 19 solution (containing dopant) 21 container L1
first path L2 second path L3 third path L4 another path 100, 150,
200, 250 apparatus for forming metal oxide film
* * * * *