U.S. patent application number 12/394797 was filed with the patent office on 2009-07-30 for film forming apparatus and film forming method.
This patent application is currently assigned to Fujikura Ltd.. Invention is credited to Kenji Goto, Takuya Kawashima, Yasuo Suzuki, Nobuo Tanabe.
Application Number | 20090191350 12/394797 |
Document ID | / |
Family ID | 37864743 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090191350 |
Kind Code |
A1 |
Goto; Kenji ; et
al. |
July 30, 2009 |
FILM FORMING APPARATUS AND FILM FORMING METHOD
Abstract
A film forming apparatus is provided which includes a device A
that generates liquid fine particles having controlled particle
diameters; a device B including a via for guiding the generated
liquid fine particles while controlling a temperature thereof; a
device C that sprays the guided liquid fine particles; and a device
D including a space for forming a transparent conductive film by
coating the sprayed liquid fine particles onto a subject to be
processed.
Inventors: |
Goto; Kenji; (Kohtoh-ku,
JP) ; Kawashima; Takuya; (Kohtoh-ku, JP) ;
Tanabe; Nobuo; (Kohtoh-ku, JP) ; Suzuki; Yasuo;
(Kohtoh-ku, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Fujikura Ltd.
Tokyo
JP
|
Family ID: |
37864743 |
Appl. No.: |
12/394797 |
Filed: |
February 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12046963 |
Mar 12, 2008 |
|
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12394797 |
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Current U.S.
Class: |
427/421.1 |
Current CPC
Class: |
C03C 2217/231 20130101;
C23C 18/1216 20130101; C03C 17/253 20130101; C03C 17/001 20130101;
C23C 18/1258 20130101; C03C 2217/24 20130101; Y02E 10/50 20130101;
C03C 2218/112 20130101; C03C 17/002 20130101; H01L 31/1884
20130101; C03C 17/25 20130101; C23C 18/02 20130101 |
Class at
Publication: |
427/421.1 |
International
Class: |
B05D 1/02 20060101
B05D001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2005 |
JP |
2005-265301 |
Claims
1. A film forming method for forming a film on a base material by
spray pyrolysis deposition comprising: generating liquid fine
particles having controlled particle diameters; guiding the liquid
fine particles through a via while performing temperature control;
and spraying the liquid fine particles onto the base material, thus
forming a film thereon.
2. The film forming method of claim 1, wherein spraying the liquid
fine particles comprises spraying the liquid fine particles from at
least one nozzle, wherein at an intake portion of the nozzle a face
velocity is V.sub.1, at a discharge portion of the nozzle, a face
velocity is V.sub.2, and V.sub.2>1.5.times.V.sub.1.
3. The film forming method of claim 2, wherein a cross-sectional
area of the intake portion is E.sub.1, a cross-sectional area of
the discharge portion is E.sub.2, and
E.sub.1>1.5.times.E.sub.2.
4. The film forming method of claim 1, wherein spraying the liquid
fine particles comprises spraying the liquid fine particles from at
least one nozzle while moving the at least one nozzle in a
substantially horizontal reciprocating movement.
5. The film forming method of claim 4, further comprising moving
the at least one nozzle away from the base material during the
reciprocating movement when the nozzle is changing direction.
Description
[0001] This is a divisional of application Ser. No. 12/046,963,
filed Mar. 12, 2008 which claims priority from Japanese Patent
Application No. 2005-265301, filed Sep. 13, 2005, the contents of
which are incorporated herein by reference.
TECHNICAL FIELD
[0002] Apparatuses and methods consistent with the present
invention relate to a film forming apparatus and a film forming
method that are suitably used when a transparent conductive film or
the like is being formed on a base material using a spray pyrolysis
deposition (SPD) method, and that make it possible to spray
droplets whose particle diameters have been made uniform in
advance.
BACKGROUND ART
[0003] In solar cells, liquid crystal display (LCD) units, plasma
display (PDP) units and the like of the related art, a base
material with a transparent conductive film (TCF) that is obtained
by forming the transparent conductive film on the transparent base
material that is formed, for example, from glass or the like that
is a non-conductive body is widely used.
[0004] These transparent conductive films are films whose main
constituent is a conductive metallic oxide such as indium tin oxide
(ITO), tin oxide (TO), and fluorine-doped tin oxide (FTO), and have
a combination of excellent transparency to visible light and
excellent electrical conductivity. Among these transparent
conductive films, transparent conductive films having indium tin
oxide (ITO), in particular, as their main constituent are widely
known, and these are used in the liquid crystal display (LCD) units
for personal computers (PC), televisions, and mobile telephones and
the like.
[0005] One method of forming a transparent conductive film such as
indium tin oxide (ITO) on a transparent base material is spray
pyrolysis deposition (SPD).
[0006] This spray pyrolysis deposition is a technology involving a
series of reactions. In this technology, a solution constituting a
raw material is sprayed using a spraying device such as an atomizer
onto a base material that has been preheated to a film formation
temperature. In the initial stages of the resulting reaction,
crystals are formed as a result of a vaporization of the solvent
contained in the droplets that have been deposited on the surface
of the base material and a reaction of solutes in the droplets. As
the reaction progresses, droplets adhere onto the crystals (i.e., a
polycrystalline substance) that have formed on the base material,
and, as a result of a vaporization of the solvent in the droplets
and a progress of the reaction between the solutes and the crystals
underneath, crystalline (i.e., a polycrystalline substance) growth
progresses.
[0007] In this spray pyrolysis deposition, an aqueous solution or
alcohol solution of a metal inorganic salt, or an organic solution
obtained by dissolving an organic metal compound or organic
acid-base in an organic solvent, or a mixed solution obtained by
mixing these solutions, or the like is used as the favorable raw
material solution to be sprayed. The temperature of the base
material differs depending on the type of starting material or raw
material solution, however, the temperature range is set to 250 to
700.degree. C. Because the film forming apparatus used in this type
of spray pyrolysis deposition is simple and low in cost, it is
effective when forming transparent conductive films at low
cost.
[0008] A transparent conductive film (TCO: transparent conductive
oxide) is glass that has been provided with conductivity by forming
a thin film of a semiconductor ceramic such as tin-doped indium
oxide (ITO), tin oxide (TO), or fluorine-doped tin oxide (FTO) on
the surface of non-conductive glass, and has the property of
conducting electricity in spite of being transparent. Among these,
ITO, in particular, is widely known as a transparent conductive
film and is used in the liquid crystal display units of personal
computers, televisions, and mobile telephones and the like.
[0009] Using spray pyrolysis deposition, it is possible to form a
transparent conductive film or the like at low cost because the
film forming apparatus is simple and the raw material is also
comparatively low in cost. An aqueous solution or alcohol solution
of a metal inorganic salt, or an organic metal compound or organic
solvent based solution of an organic acid-base is used for the
starting material of the transparent conductive film. The
temperature of the substrate differs depending on the starting
material or raw material solution, however, the temperature range
is set to 250 to 700.degree. C.
[0010] However, in a related art film forming apparatus 1100 that
includes a liquid supply component 1120 and a vapor supply
component 1121 such as is shown in FIG. 1, in a fine particle
formation device a, liquid that is supplied from the liquid supply
component 1120 and vapor that is supplied from the vapor supply
component 1121 are made to collide with each other so that the raw
material solution formed by the two is changed into fine particles.
When the raw material in fine particle form is sprayed onto a base
material 1110 by a spray device c, the size of droplets 1122 that
are sprayed from the spray device c is dependent on the spray
nozzles (may also be hereinafter referred to as two-fluid spray
nozzles) in the spray device c, and it is difficult to obtain a
uniform size in the droplets 1122 which causes the film thickness
to be uneven. Namely, in the preparation of a transparent
conductive film using spray pyrolysis deposition inside a
transparent conductive film forming device, when spray nozzles are
used to spray a raw material solution onto a base material that has
been heated to a temperature range of 250 to 700.degree. C., the
droplets 1122 that are sprayed from the spray nozzles have a size
distribution of between 10 .mu.m and 120 .mu.m, as is shown by the
related art apparatus in FIG. 6, even when two-fluid spray nozzles
that allow fine particles to be formed are used. As a result, when
forming a film over a large surface area, in-plane distribution
ends up being generated in the sprayed droplets (i.e., mist) so
that film thickness distribution is increased and a considerably
high distribution is created in some film characteristics, such as
sheet resistance and transmissivity.
[0011] Therefore, several devices have been proposed as devices to
make the size of the sprayed droplets uniform. For example, it has
been observed that, among droplets sprayed from spray nozzles,
droplets having a large particle diameter are present in greater
numbers at positions away from the center of the spray path. It has
also been observed that coarse droplets contained in the vicinity
of the center have a fast spray speed and fly further than fine
droplets. Accordingly, technology has been proposed in which wall
surfaces are provided at a front surface and surrounding the spray
path so that droplets having a large particle diameter that fly to
positions away from the center of the spray path and coarse
droplets that fly far from the vicinity of the center collide with
these wall surfaces and are removed (see Japanese Unexamined Patent
Application, First Publication No. H05-320919 and Japanese
Unexamined Patent Application, First Publication No.
2001-205151).
[0012] However, the above described devices attempt to make the
size of the droplets uniform by efficiently selecting sprayed
droplets, and do not spray droplets whose particle sizes have
already been made uniform in advance. Accordingly, there is a limit
as to how uniform the size of the droplets can be made and it is
difficult to use only fine droplets to form a film.
[0013] Moreover, it is necessary for a sufficient distance, for
example, approximately 500 mm to be provided between the discharged
spray and the base material. This makes positive temperature
control as well as control of the droplet spray speed and of the
force of their collision with the base material impossible. As a
result, film formation in which the film characteristics are
precisely controlled has not been possible.
[0014] Another example of a related film forming apparatus that
uses spray pyrolysis deposition is shown in FIG. 2. This film
forming apparatus 2100 comprises a supporting device 2120 on which
a substrate 2110 is mounted and with a discharge device 2130 that
sprays a raw material solution in spray form. The supporting device
2120 has a heating device embedded therein that heats a mounted
substrate to a predetermined temperature (see, for example,
Japanese Unexamined Patent Application, First Publication No.
H06-012446).
[0015] In order to spray mist uniformly onto a substrate having a
large surface area at an angle of, for example, 200 mm or more, it
is necessary to arrange and drive a large number of mist spray
nozzles.
[0016] However, if mist is sprayed using related art circular
nozzles (i.e., 60.phi. mm), then as is shown in FIGS. 3A and 3B, if
the nozzles are driven in a circular shape or, as is shown in FIGS.
4A and 4B, if the nozzles are driven in an elliptical shape, the
distribution is increased in the sprayed quantity of the mist. In
order to reduce the effects of this distribution, it has been
necessary to conduct even more complex drive control.
SUMMARY OF THE INVENTION
[0017] It is an exemplary object of the present invention to
provide a film forming apparatus and a film forming method that
make it possible to spray droplets whose particle diameters have
been made uniform in advance.
[0018] It is a further exemplary object of the present invention to
provide a film forming apparatus and a film forming method that
make it possible to spray mist uniformly over a substrate having a
large surface area and to make the thickness of the formed film
uniform.
[0019] Exemplary embodiments of the present invention address the
objects described above and other objects not described. Also, the
present invention is not required to address the above-described
objects.
[0020] Exemplary embodiments of the present invention provide the
following film forming apparatus and film forming method that
employ spray pyrolysis deposition.
[0021] Namely, a film forming apparatus that uses spray pyrolysis
deposition according to a first aspect of the present invention
includes: a device A that generates liquid fine particles, the
liquid fine particles having controlled particle diameters; a
device B that is defined by a space for guiding the generated
liquid fine particles while controlling a temperature thereof; a
device C that sprays the guided liquid fine particles; and a device
D that is defined by a space for forming a transparent conductive
film by coating the sprayed liquid fine particles onto a subject to
be processed.
[0022] In this film formation apparatus that uses spray pyrolysis
deposition a structure is employed in which, in the device A,
liquid fine particles are generated whose particle diameters have
been made uniform in advance by controlling the particle diameter
of sprayed droplets. Next, in the device B, only liquid fine
particles whose particles diameters have been made uniform are
transported to the device C. Thereafter, in the device C, only
minute liquid fine particles whose particle diameters have already
been made uniform are sprayed onto a base material (i.e., a subject
to be processed) that is placed in the space of the device D.
[0023] As a result, it is possible to form a film that has little
unevenness in the film thickness.
[0024] In a film forming apparatus that uses spray pyrolysis
deposition according to a second aspect of the present invention,
in the device B, the space for guiding the liquid fine particles
may be isolated from the outside by a partitioning member that has
water repellency or has an internal surface that is undergone water
repellency treatment. Water repellency may be achieved by providing
a coating film that is suitable for imparting water repellency,
such as Teflon.RTM. resin or a vinyl chloride resin or the like,
and providing conditions of a contact angle of 80.degree. or more
for the contact between the liquid fine particles and the interior
wall of the delivery path that transports the liquid fine particles
while guiding them.
[0025] By employing this type of structure, it is possible to
reduce effects from the outside temperature while suppressing
adhesion of the liquid fine particles to the partitioning
plate.
[0026] In a film forming apparatus that uses spray pyrolysis
deposition according to a third aspect of the present invention, in
the device B, it is also possible for the space for guiding the
liquid fine particles to be isolated from the outside by a
partitioning member and to have a mechanism that performs
temperature control such that a temperature inside the space is
kept at a higher temperature than the outside.
[0027] By employing this type of structure, adhesion of liquid fine
droplets to the interior wall of the delivery path due to
condensation or the like and a bonding together of the liquid fine
particles can be suppressed so that it is possible to supply,
stably, liquid fine particles whose particle diameters have been
made uniform to the device C.
[0028] A film forming apparatus according to a fourth aspect of the
present invention is a film forming apparatus that forms a thin
film on a surface of a subject to be processed by spray pyrolysis
deposition and includes: a supporting device on which the subject
to be processed is mounted; and a discharging device that sprays a
mist containing a raw material solution for the thin film towards a
surface of the subject to be processed, wherein the discharge
device comprises nozzles, each nozzle having a first position that
forms a mist intake side and a second position that forms a mist
discharge side, and if a face velocity at the first position is
taken as V.sub.1 and a face velocity at the second position is
taken as V.sub.2, a face velocity of the mist moving through the
nozzles is V.sub.2>1.5.times.V.sub.1.
[0029] In a film forming apparatus according to a fifth aspect of
the present invention, in the above described film forming
apparatus 1, in the nozzles, if a cross-sectional area of the first
portion when seen from the discharge aperture side is taken as
E.sub.1 and a cross-sectional area of the second portion is taken
as E.sub.2, E.sub.1>1.5.times.E.sub.2.
[0030] In a film forming apparatus according to a sixth aspect of
the present invention, in the above described film forming
apparatus, the shape of the nozzles at the second position is a
slit shape.
[0031] In a film forming apparatus according to a seventh aspect of
the present invention, in the above described film forming
apparatus, there are further provided: a preparation chamber where
the mist is generated by spraying in advance the raw material
solution; and a transporting device that is defined by a space that
enables the mist to move from the preparation chamber to the
nozzles.
[0032] In a film forming apparatus according to an eighth aspect of
the present invention, in the above described film forming
apparatus, during film formation the nozzles are shifted in a
horizontal direction relative to a surface of the subject to be
processed.
[0033] In a film forming apparatus according to a ninth aspect of
the present invention, in the above described film forming
apparatus, if the movement in a horizontal direction of the nozzles
is a reciprocating movement, then in a vicinity of a turn portion,
the nozzles are shifted in a direction in which they move away from
the surface of the subject to be processed.
[0034] A film forming method according to a tenth aspect of the
present invention is a film forming method for forming a film on a
base material by spray pyrolysis deposition that includes:
generating liquid fine particles having controlled particle
diameters; performing temperature control on generated liquid fine
particles and guiding them with the particle diameters thereof made
uniform; spraying the guided liquid fine particles; and forming a
film by causing the sprayed liquid fine particles to accumulate on
the base material.
[0035] As a result of the above, because it is possible to form a
film using only liquid fine particles whose particle diameters have
been made precisely uniform, it is possible to form a film having
little film thickness distribution.
[0036] According to the film forming apparatus that uses spray
pyrolysis deposition of an exemplary embodiment of the present
invention, by introducing liquid fine particles, whose particle
diameters are controlled, via a space that guides them while
controlling their temperature to nozzles serving as a spraying
device, it becomes possible for the in-plane distribution of the
liquid fine particles that are sprayed from the nozzles to be made
uniform, and the in-plane distribution range of the film
characteristics can be contracted (i.e., narrowed).
[0037] Consequently, a film forming apparatus according to an
exemplary embodiment of the present invention contributes to fields
in which a transparent conductive film having a large surface area
is required, for example, fields such as liquid crystal display
devices and EL display devices.
[0038] In an exemplary film forming method of the present
invention, because a transparent conductive film is formed using
liquid fine particles whose particle diameters have been made
uniform, it becomes possible to form a uniform and homogeneous film
irrespectively of the surface area of the base material (i.e., the
subject to be processed).
[0039] Consequently, the construction of a production system that
produces, in large quantities, transparent conductive films having
a large surface area is possible.
[0040] According to an exemplary embodiment of the present
invention, if nozzles are provided in a discharge device that
sprays mist that is formed by the raw material solution of a thin
film, by stipulating that a relationship between a face velocity
V.sub.1 of the mist at a first position and a face velocity V.sub.2
of the mist at a second position satisfy
V.sub.2>1.5.times.V.sub.1, it becomes possible to provide a film
forming apparatus that is capable of achieving a uniform spray
amount over the entire surface of a subject to be processed and of
achieving an improvement in the film formation speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a schematic view showing the structure of a
related art film forming apparatus.
[0042] FIG. 2 is a view schematically showing an example of a
related art film forming apparatus.
[0043] FIG. 3A is a view showing a nozzle driving pattern and a
sprayed mist distribution.
[0044] FIG. 3B is a view showing a nozzle driving pattern and a
sprayed mist distribution.
[0045] FIG. 4A is a view showing a nozzle driving pattern and a
sprayed mist distribution.
[0046] FIG. 4B is a view showing a nozzle driving pattern and a
sprayed mist distribution.
[0047] FIG. 5 is a schematic view showing the structure of an
example of a film forming apparatus of an exemplary embodiment of
the present invention.
[0048] FIG. 6 is a view showing a size distribution of fine
particles in liquid form controlled by a film forming apparatus of
an exemplary embodiment of the present invention as compared with a
conventional apparatus.
[0049] FIG. 7 is a view schematically showing another example of a
film forming apparatus of an exemplary embodiment of the present
invention.
[0050] FIG. 8 is a view showing the nozzles shown in FIG. 7.
[0051] FIG. 9 is a view showing a nozzle driving pattern and a
sprayed mist distribution.
[0052] FIG. 10 is a view showing a nozzle driving pattern and a
sprayed mist distribution.
[0053] FIG. 11 is a view showing a placement and driving of
nozzles.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0054] A first exemplary embodiment of the present invention will
now be described.
[0055] FIG. 5 is a schematic view showing a structure of a film
forming apparatus according to the present embodiment.
[0056] A film forming apparatus 11 according to the present
embodiment comprises a device A (hereinafter referred to as a
"liquid fine particle generating device") that generates first
liquid fine particles whose particle diameter is controlled, a
device B (hereinafter referred to as a "liquid fine particle
guiding device") that is defined by a space that guides the
generated first liquid fine particles while performing temperature
control thereof, a device C (hereinafter referred to as a "liquid
fine particle spraying device") that converts the guided first
liquid fine particles into finer second liquid fine particles 12
and then sprays these, and a device D (hereinafter referred to as a
"transparent conductive film forming device") that is defined by a
space that makes the sprayed second liquid fine particles 12 coated
onto a subject to be processed (i.e., base material) in the form of
a glass substrate 110 so as to form a transparent conductive
film.
[0057] The liquid fine particle generating device A controls
droplets that have been sprayed preliminarily using a spray device
that is different from the liquid fine particle spraying device C
(described below) so as to make a selection such that only droplets
having a small diameter (i.e., fine droplets) are efficiently
extracted as first liquid fine particles so that the size thereof
is made uniform.
[0058] The generated first liquid fine particles may contain
between 60.0% by volume and 98.8% by volume of air.
[0059] The liquid fine particles guiding device B has a delivery
path in the form of a space where the first liquid fine particles
that were generated with a controlled particle diameter by the
liquid fine particle generating device A are transported while
being guided such that there is no damage to the particle diameter
from the liquid fine particle generating device A as far as the
subsequent liquid fine particle spraying device C.
[0060] This delivery path is isolated from the outside by a
partitioning member, and is controlled such that the temperature of
the interior walls is the same as or higher than that of the liquid
fine particles. In addition, the temperature thereof is maintained
such that the evaporation rate of the solvent in the transparent
conductive film raw material solution does not become excessive.
Namely, such that a relationship is established whereby the liquid
fine particle temperature>delivery path internal wall
temperature>solvent evaporation temperature.
[0061] In addition, a flow having a flow rate of between 100 cm/min
and 100,000 cm/min is present in the liquid fine particles inside
the delivery.
[0062] Moreover, the interior walls of the delivery path are
isolated from the outside by using a material having water
repellency such as a fluororesin or the like, or by performing
processing to impart water repellency to the surfaces thereof. At
this time, if a material having excellent heat propagation
properties such as a metal is used for the delivery, then it is
easily affected by the outside temperature and may lead to liquid
fine particles adhering to the interior walls of the delivery.
Because of this, a resin material having low heat propagation such
as a vinyl chloride resin or a fluororesin or the like may be used.
Note that if a metal material is used, this can be addressed by
performing temperature control on the outside walls of the
delivery.
[0063] Moreover, if hydrochloric acid, sulfuric acid, or nitric
acid is used for the chemical solution, then it is necessary to use
a material having chemical resistant properties for the interior
walls that are in direct contact with the liquid fine particles, or
to perform surface treatment thereon using a material having
chemical resistant properties.
[0064] Furthermore, the distance of the delivery path may be short.
However, it is also possible to think of cases when some distance
is required from the viewpoint of design such as restrictions
imposed by the temperature of the liquid fine particles and the
temperature of the interior walls, and the placement from various
devices. When this distance is increased, it may be less than 10
meters.
[0065] The liquid fine particle spray device C sprays liquid fine
particles that have been guided by the liquid fine particle guiding
device B onto the glass substrate 110 that is placed in the space
of the subsequent transparent conductive film forming device D.
Liquid fine particles are sprayed at a flow rate of between 1,000
cm/min and 100,000 cm/min from a discharge aperture in the liquid
fine particle spraying device C. The distance between the discharge
aperture in the liquid fine particle spraying device C and the
surface of the glass substrate 110 is controlled so as to be
between 5 mm and 200 mm.
[0066] The transparent conductive film forming device D is
positioned facing the discharge aperture in the liquid fine
particle spraying device C and comprises a space for mounting the
glass substrate 110 on which the liquid fine particles that form a
transparent conductive film are deposited. In the transparent
conductive film forming device D, a raw material solution for a
transparent conductive film that contains conductive polymers that
have been sprayed onto the glass substrate 110 is coated so as to
form an initial layer of the transparent conductive film.
[0067] The surface of the glass substrate 110 is heated by heat
transfer from a substrate heater located beneath it, heat ray
irradiation from a heat ray heater located above it, and by a high
temperature flow from an upper atmosphere, so that the temperature
range is controlled to between 200.degree. C. and 600.degree.
C.
[0068] Next, the film forming method for forming the transparent
conductive film according to the present embodiment will be
described.
[0069] Firstly, liquid fine particles whose particle diameter is
controlled by the liquid particle generating device A are
generated. Next, the temperature of the generated liquid fine
particles is controlled by the liquid fine particle guiding device
B and the liquid fine particles having uniform particle diameters
are guided to the liquid fine particle spraying device C.
Thereafter, the guided liquid fine particles are sprayed onto a
subject to be processed by the liquid fine particle spraying device
C and the liquid fine particles 12 that have been sprayed in the
transparent conductive film forming device D are deposited on the
glass substrate 110 that is serving as a subject to be processed so
that a film is formed.
[0070] The film forming apparatus according to a second exemplary
embodiment of the present invention will now be described based on
the drawings.
[0071] FIG. 7 is a view schematically showing a film forming
apparatus according to the second embodiment of the present
invention
[0072] A film forming apparatus 21 is a film forming apparatus that
forms a thin film on a subject 22 to be processed by spray
pyrolysis deposition and includes a supporting device 211 on which
the subject to be processed 22 is mounted, and a discharging device
212 that sprays a mist 23 that is formed from a raw material
solution for the thin film onto a surface of the subject 22 to be
processed.
[0073] Moreover, in a film forming apparatus 21 of this embodiment,
the nozzle provided in the discharge device 212 has a first portion
212a that forms the mist intake side and a second portion 212b that
forms the mist discharge side, and a third portion 212c. Regarding
the face velocity of mist moving through the nozzle, the face
velocity V.sub.1 in the first portion 212a and the face velocity
V.sub.2 of the second portion 212b are set so as to satisfy the
following formula.
V.sub.2>1.5.times.V.sub.1 (1)
[0074] By regulating the face velocity V.sub.1 of the mist in the
first portion 212a and the face velocity V.sub.2 of the mist in the
second portion 212b in the manner described above, the sprayed mist
quantity over the entire surface of the subject 22 to be processed
is made uniform and the film formation rate can be increased.
[0075] The supporting device 211 has a temperature control device
embedded therein that includes functions of heating, maintaining
the temperature of, and cooling the subject 22 to be processed in
order to form a thin film while keeping the surface of the subject
22 to be processed on which a film is being formed at a
predetermined temperature. The temperature control device is, for
example, a heater.
[0076] The discharge device 212 sprays mist 23 onto the subject 22
to be processed that is placed in a space in a film formation
chamber 210. The mist 23 is sprayed at a flow rate of between 100
cm/min and 100,000 cm/min from the discharge aperture of the
discharge device 212. The distance between the discharge device 212
and the surface of the subject to be processed 2 is controlled
between 5 mm and 200 mm.
[0077] The discharge device 212 is, for example, a nozzle.
Moreover, the raw material solution that is sprayed from the
discharge device 212 is the mist 23 (i.e., liquid fine
particles).
[0078] This mist 23 may also be generated by spraying raw material
solution in advance in a preparation chamber 220 (described
below).
[0079] In addition, the surface of the subject 22 to be processed
is heated by heat transfer or the like from the temperature control
device, and the temperature range is controlled to between
200.degree. C. and 600.degree. C.
[0080] In the film forming apparatus 21 of the present invention,
in the nozzle provided in the discharge device 212, when viewed
from the discharge aperture side a cross-sectional area E.sub.1 of
the first portion 212a and a cross-sectional area E.sub.2 of the
second portion 212b are set so as to satisfy the following
formula.
E.sub.1>1.5.times.E.sub.2 (2)
[0081] In the nozzle, by regulating the cross-sectional area
E.sub.1 of the first portion 212a and the cross-sectional area
E.sub.2 of the second portion 212b in the above manner, the face
velocity of the mist moving inside the nozzle can be easily changed
between the first portion 212a and the second portion 212b. Note
that the cross-sectional areas E.sub.1 and E.sub.2 are the
cross-sectional areas of the nozzle internal dimension.
[0082] Specifically, a relationship between the mist face velocity
V.sub.1 in the first portion 212a and the mist face velocity
V.sub.2 in the second portion 212b can be set to
V.sub.2>1.5.times.V.sub.1.
[0083] The first portion 212a may be circular and the second
portion 212b may be slit-shaped. By making the second portion 212b
that forms the discharge aperture slit-shaped, mist can be sprayed
uniformly even onto a subject to be processed that has a large
surface area so that a film can be formed uniformly.
[0084] Furthermore, in a slit-shaped discharge aperture, as is
shown in FIG. 8, the nozzle shape is designed such that no
difference is generated between the mist flow rate in a center
portion and the mist flow rate at end portions. FIG. 8 is an view
of a nozzle portion.
[0085] As is shown in FIG. 8, an inner diameter H of the first
portion 212a (i.e., a cylindrical portion), a length X and a width
Y of the aperture portion of the second portion 212b (i.e., a slit
portion), a length G of the second portion 212b, and a length F of
a third portion (i.e., a constricted portion) that connects the
first portion 212a to the second portion 212b are set so as to
satisfy the following formula.
(X-H)<2.5.times.F (F.ltoreq.G) (3)
[0086] By designing the nozzle shape such that Formula (3) is
satisfied, the mist flow rate in a slit-shaped discharge aperture
can be made equal in a center portion and at end portions, and mist
can be sprayed uniformly onto the subject 22 to be processed.
[0087] Moreover, during film formation, the nozzle is moved in a
horizontal direction along one surface of the subject 22 to be
processed. By moving the nozzle, a film can be formed uniformly
even on a subject to be processed that has a large surface
area.
[0088] At this time, by making the movement of the nozzle in a
horizontal direction a reciprocating movement, it becomes possible
to form a film on a subject to be processed that has a larger
surface area, however, as is shown in FIG. 9, there is a tendency
for the spray quantity distribution to become concentrated in
driving turning portions (i.e., in turn portions). This is because
it is difficult to control the nozzle during turning. Namely, at
the stage when nozzle turn control is begun, the nozzle shift speed
is decreased so that the spray quantity in these areas
increases.
[0089] Therefore, in order to avoid the sprayed mist quantity
becoming concentrated in turn portions, at the stage when nozzle
turn control is begun, the spray height of the nozzle may be
controlled proportionally as the nozzle shift speed is
decreased.
[0090] Namely, in the film forming apparatus 21, if the movement of
the nozzle in a horizontal direction is a reciprocating movement,
then as is shown in FIG. 10, in the vicinity of the turn portions
the nozzle is moved in a direction in which it moves away from a
surface of the subject 22 to be processed.
[0091] In end portions of the subject 22 to be processed which form
turn portions in a reciprocating movement, by performing film
formation while raising the height of the nozzle from the surface
of the subject 22 to be processed, the sprayed mist quantity can be
made uniform over the entire surface of the subject 22 to be
processed. As a result, it is possible to reduce any unevenness in
the film thickness of a formed thin film.
[0092] Moreover, this film forming apparatus 21 is further provided
with a preparation chamber 220 that generates the mist 23 by
spraying a raw material solution in advance, and a transporting
device that is defined by a space and moves the mist 23 from the
preparation chamber 220 to the discharge device 212.
[0093] In the preparation chamber 220, the raw material solution is
sprayed in advance using a spraying device that is different from
the above described spraying device 212 and control is performed to
make a selection such that only droplets having a small diameter
(i.e., fine) are efficiently extracted as the mist 23 so that the
size thereof is made uniform. Because a finer mist can be sprayed a
film having good characteristics can be formed.
[0094] The generated mist 23 may contain between 60.0% by volume
and 98.8% by volume of air.
[0095] The transporting device has a delivery path 221 in the form
of a space where the generated mist 23 is transported while being
guided.
[0096] The delivery path 221 is isolated from the outside by a
partitioning member, and is controlled such that the temperature of
the interior walls is the same as or higher than that of the mist
23. In addition, the temperature thereof is maintained such that
the evaporation rate of the solvent in the raw material solution
does not become excessive. Namely, a relationship whereby the mist
23 temperature>delivery path 221 internal wall
temperature>solvent evaporation temperature.
[0097] In addition, a flow having a flow rate of between 100 cm/min
and 100,000 cm/min is present in the mist 23 inside the delivery
path 221.
[0098] Moreover, the interior walls of the delivery path 221 are
isolated from the outside by using a material having water
repellency such as a fluororesin or the like, or by performing
processing to impart water repellency to the surfaces thereof. At
this time, if a material having excellent heat propagation
properties such as a metal is used for the delivery path 221, then
it is easily affected by the outside temperature and may lead to
the mist 23 adhering to the interior walls of the delivery. Because
of this, a resin material having low heat propagation such as a
vinyl chloride resin or a fluororesin or the like may be used. Note
that if a metal material is used, this can be addressed by
performing temperature control on the outside walls of the
delivery.
[0099] Moreover, if a chemical solution, such as hydrochloric acid,
sulfuric acid, or nitric acid, is used, then it is necessary to use
a material having chemical resistant properties for the interior
walls that are in direct contact with the mist 23, or to perform
surface treatment thereon using a material having chemical
resistant properties.
[0100] Furthermore, the distance of the delivery path 221 may be
short. However, it is also possible to think of cases when some
distance is required from the viewpoint of design such as
restrictions imposed by the temperature of the liquid fine
particles and the temperature of the interior walls, and the
placement from various devices. When this distance is increased, it
may be less than 10 meters.
[0101] Moreover, in this film forming chamber, a space that
includes the subject 22 may be processed and the discharge device
212 may be enclosed in a hood 214.
[0102] The hood 214 is formed from a non-corrosive metal such as
stainless steel. Aperture portions are formed on both sides in the
vicinity of the bottom portion.
[0103] In the film forming apparatus 21, because the hood 214 is
positioned so as to enclose the space between the discharge device
212 and the subject 22 to be processed that is placed in a position
facing the discharge device 212, raw material solution that is
discharged in spray form from the discharge aperture of the
discharge device 212 is not affected by the outside air, and a
state can be stably maintained in which the raw material solution
is sprayed from the discharge aperture into a radial space in the
direction of the subject 22 to be processed. In other words, the
hood 214 also helps to prevent raw material solution scattering
from the space inside the hood 214 to the outside of the apparatus
and causing an unnecessary increase in the amount used. As a
result, the raw material solution is used effectively to form a
thin film.
[0104] Moreover, because the hood 214 is positioned so as to
enclose the space between the discharge device 212 and the subject
22 to be processed, during film formation, heat dissipation from
the subject 22 to be processed can be suppressed. As a result, it
becomes possible to reduce the amount of heat that is required to
heat the subject 22 to be processed and the controllability of the
surface temperature of the subject 22 to be processed is
improved.
[0105] Next, a method of forming a thin film on the subject 22 to
be processed by spray pyrolysis deposition using this film forming
apparatus 21 will be described.
[0106] Note that in the description given below, the description
uses as an example a case in which an ITO film is formed as a
transparent conductive film on a substrate in the form of the
subject 22 to be processed using the film forming apparatus 21 of
the present embodiment, however, the present invention is not
limited to this and can also be used to form a variety of thin
films.
[0107] Firstly, a substrate whose surface is a clean surface is
mounted on a base and this substrate and base are held together in
a predetermined position.
[0108] A glass plate having a thickness of approximately between
0.3 mm and 5 mm that is formed from a glass such as, for example,
soda glass, heat-resistant glass, or quartz glass may be used for
the substrate.
[0109] Once the substrate surface temperature has reached a
predetermined temperature and stabilized, formation of the ITO film
commences.
[0110] In the preparation chamber 220, the raw material solution
for the ITO film is sprayed in preparation using a spraying device
so as to form the mist 23.
[0111] A solution containing components that form a conductive
metallic oxide such as indium tin oxide (ITO) or the like as a
result of being heated may be used as the raw material solution for
the ITO film.
[0112] An aqueous solution or ethanol solution or ethanol-water
mixture solution containing 0.01 mol/L of tin chloride pentahydrate
in an aqueous solution or ethanol solution or ethanol-water mixture
solution containing 0.2 mol/L of indium chloride tetrahydrate may
be used as the raw material solution for the ITO film.
[0113] The mist 23 that is generated in the preparation chamber 220
is transported via the delivery path 221 to the film formation
chamber 210, and is then sprayed from the nozzle (i.e., the
discharge device 212) located in the top of the film formation
chamber 210 towards the top of the substrate. As a result of this
mist 23 adhering to the surface of the substrate that has been
heated to a predetermined temperature, the solvent in the mist is
rapidly evaporated and any remaining solute undergoes a rapid
chemical reaction and changes into a conductive metallic oxide such
as ITO or the like. As a result, crystals that are formed by the
conductive metallic oxide are rapidly generated on the surface of
the substrate and a transparent conductive film (i.e., an ITO film)
is formed over a short period of time.
[0114] At this time, if the face velocity of the mist moving
through the nozzle is designated such that the face velocity at the
first portion 212a, which is the mist intake side, is taken as
V.sub.1 and the face velocity at the second portion 212b, which is
the mist discharge side, is taken as V.sub.2, then
V.sub.2>1.5.times.V.sub.1. The second portion 212b that forms
the discharge aperture is slit-shaped.
[0115] The nozzle is further moved in a horizontal direction along
one surface of the substrate. If this movement of the nozzle in a
horizontal direction is a reciprocating movement, then in the
vicinity of the turn portion, the nozzle is moved in a direction in
which it moves away from the surface of the substrate.
[0116] Once the formation of the ITO film is completed, it is
cooled until the substrate temperature reaches a predetermined
temperature and the substrate is then removed.
[0117] In this manner, a transparent conductive film that is made
up of an ITO film is formed on the substrate.
[0118] In this film forming apparatus 21, if the face velocity of
the mist moving through the nozzle is designated such that the face
velocity at the first portion 212a, which is the mist intake side,
is taken as V.sub.1 and the face velocity at the second portion
212b, which is the mist discharge side, is taken as V.sub.2, then
V.sub.2>1.5.times.V.sub.1. By this means, the amount of mist
sprayed over the entire surface of the subject 22 to be processed
can be made uniform, and it is possible to improve the film forming
speed.
[0119] Furthermore, the nozzle is moved in a horizontal direction
along one surface of the subject 22 to be processed. If this
movement of the nozzle in a horizontal direction is a reciprocating
movement, then in the vicinity of the turn portion, the nozzle is
moved in a direction in which it moves away from the surface of the
subject 22 to be processed. By this means, the amount of mist
sprayed over the entire surface of the subject 22 to be processed
can be made uniform.
[0120] As a result, a transparent conductive film that is obtained
in this manner ends up having suppressed unevenness in the film
thickness distribution over a large surface area. In addition, the
in-plane uniformity of thin film characteristics such as, for
example, sheet resistance and transmissivity is ensured, and a high
quality product is obtained.
[0121] A description has been given above of film forming
apparatuses of exemplary embodiments of the present invention,
however, the present invention is not limited to the above examples
and can be appropriately altered as is necessary.
EXAMPLES
[0122] Next, examples of the present invention will be described.
These are specific examples that make it possible for the present
invention to be more fully understood, however, the present
invention is not limited to these examples.
First Example
[0123] Firstly, in Example 1-1, an indium tin oxide (ITO) film is
formed as a transparent conductive film. The solution that forms
the raw material for this ITO film was prepared by dissolving 5.58
g of indium chloride (III) pentahydrate (InCl.sub.3.5H.sub.2O,
molecular weight: 293.24) and 0.32 g of tin chloride (IV)
pentahydrate (SnCl.sub.4.5H.sub.2O, molecular weight: 350.60) in
100 ml of pure water serving as a solvent.
[0124] In Example 1-1, using the conditions shown in Table 1 below,
liquid fine particles that were generated by the liquid fine
particle generating device A were guided to the liquid fine
particle guiding device B. Moreover, a bellows pipe made from vinyl
chloride that can be elongated or contracted was used for the
delivery path of the liquid fine particle guiding device B that
guides the liquid fine particles, and water repellency was ensured
by treating the internal surface thereof with a fluororesin.
TABLE-US-00001 TABLE 1 Item Parameter Starting raw material
InCl.sub.3.cndot.5H.sub.2O, SnCl.sub.4 Solvent Water Temperature of
liquid fine particles after generation 23.degree. C. Temperature of
liquid fine particles inside 23.degree. C. delivery path Delivery
path exterior temperature 22.degree. C. Proportion of droplets in
liquid fine particles 1.5% by volume Flow rate of liquid fine
particles being transported 7,000 cm/min Length of delivery path
2.0 m
[0125] Moreover, in Example 1-1, using the conditions shown in
Table 2 below, liquid fine particles that were guided by the liquid
fine particle guiding device B were sprayed by the nozzle of the
liquid fine particle spraying device C onto the glass substrate 110
serving as a subject to be processed.
TABLE-US-00002 TABLE 2 Item Parameter Nozzle aperture size 60
.phi.mm Liquid fine particle temperature (at nozzle aperture)
40.degree. C. Flow rate of liquid fine particles at nozzle aperture
15,000 cm/min Number of nozzles 4 Distance between nozzle and base
material 20 mm Spraying time 15 min.
[0126] The volume distribution ratio relative to the particle
diameter of the liquid fine particles generated on the basis of the
above conditions was then measured and the droplet size
distribution thereof was compared with that of droplets generated
using a conventional apparatus in which the vapor supplied from the
vapor supply component and the liquid that is supplied from the
liquid supply component are made to collide with each other so that
the raw material solution formed by the two is changed into fine
particles, and this raw material solution that has been changed
into fine particles is sprayed onto a base material by two-fluid
spray nozzles. Note that a microscopic mist generating apparatus
manufactured by Atomax Co. Ltd. was used for the spray nozzles in
the present example. The results are shown in FIG. 6.
[0127] As is shown in FIG. 6, in a related art apparatus the
droplet size distribution is between 9 .mu.m and 160 .mu.m, while
in an apparatus that is based on the present example the droplet
size distribution is between 1 .mu.m and 60 .mu.m so that the size
of the droplet size distribution is reduced. As a result, droplets
of 70 .mu.m or larger can be removed and it becomes possible to
spray droplets that have a uniform particle diameter.
[0128] Moreover, in Example 1-1, a borosilicate glass plate having
a size of 500 mm.times.500 mm and a thickness of 2 mm was used for
the base material, and the film thickness, sheet resistance, and
transmissivity to visible light of an ITO film that was formed
under the above described conditions with the surface temperature
of the glass substrate set to 350.degree. C. were each measured and
compared with the same measurement results from a related art
apparatus. The results are shown in Table 3.
TABLE-US-00003 TABLE 3 Related Item Example 1-1 apparatus Art
apparatus Surface temperature of glass 350.degree. C. 350.degree.
C. substrate Film thickness distribution 610 to 650 nm 620 to 750
nm Sheet resistance distribution 3 to 5 .OMEGA./cm.sup.2 10 to 35
.OMEGA.cm.sup.2 Transmissivity 80% 70%
[0129] From the results in Table 3, it can be understood that, in
an apparatus that is based on an exemplary embodiment of the
present invention, it is possible to contribute to the uniformity
of the film thickness distribution and to the uniformity of the
sheet resistance distribution, and to improve the film quality
including transmissivity.
[0130] Moreover, in Example 1-1, using a borosilicate glass plate
having a size of 500 mm.times.500 mm and a thickness of 2 mm for
the base material, in order to achieve a 500 mm.times.500 mm film
formation, on the substrate side this glass plate was driven
.+-.150 mm in a direction taking a horizontal direction as the X
axis, and on the nozzle side was driven .+-.100 mm in a direction
taking a horizontal direction that is orthogonal to the X axial
direction on the substrate side as the Y axis. Accordingly, a
substrate-nozzle direction that is vertically orthogonal to both
the X axial direction on the substrate side and the Y axial
direction on the nozzle side is taken as a Z axial direction. The
substrate was then heated under the combined conditions (A)+(B)
shown in Table 4 below.
TABLE-US-00004 TABLE 4 Item Parameter Type of coated film
Borosilicate glass (TEMPAX #8330) substrate Coated film substrate
500 .times. 500 .times. 2 mm size Coated film substrate 300 to
450.degree. C. surface temperature Heating conditions (A) Heat
transfer heating from substrate rear surface side + (B) Heat ray
irradiation heating from substrate front surface (i.e., formed film
surface) side Drive method (for film Drive in X axial direction of
substrate side formation over a (.+-.150 mm) + drive in Y axial
direction of large surface area) nozzle side (.+-.150 mm)
[0131] The film thickness distribution, sheet resistance
distribution, and transmissivity distribution in visible light of
an ITO film that was formed under the above described conditions
were each measured and compared with the same measurement results
from a related art apparatus. The results are shown in Table 5.
Note that the film formation time was 15 minutes for both the
apparatus of the present example and the conventional
apparatus.
TABLE-US-00005 TABLE 5 Related Item Example 1-1 apparatus art
apparatus Film thickness distribution 700 to 900 nm 200 to 1200 nm
Sheet resistance distribution 3 to 4 .OMEGA./cm.sup.2 5 to 15
.OMEGA./cm.sup.2 Transmissivity distribution 75 to 83% 60 to 82%
(overall light ray transmissivity) Film formation time 15 min.
[0132] From the results shown in Table 5, it can be understood that
in the same film formation time the film growth is more rapid and
there is reduced film thickness distribution and sheet resistance
distribution, and there is also a significant improvement in the
transmissivity characteristic.
[0133] It is thought that this is an effect of the fact that the
in-plane distribution of the liquid fine particles that are sprayed
from the nozzles have been made uniform, the fact that it has
become possible to spray with the nozzles placed in close proximity
to the substrate (i.e., conventionally, 500 mm compared to 20 mm in
Example 1-1), the fact that it is possible to control the flow rate
of the liquid fine particles that are sprayed from the nozzles, and
the fact that it is possible to control the temperature of the
liquid fine particles until they reach the substrate.
Example 2
[0134] Using a film forming apparatus of an exemplary embodiment of
the present invention, an ITO film was formed as a transparent
conductive film on the substrate.
[0135] Firstly, a raw material solution was prepared in the manner
described below.
Preparation of ITO Raw Material Solution
[0136] The solution was prepared by dissolving chemical agents in a
ratio of 5.58 g/100 ml of indium chloride (III) tetrahydrate
(InCl.sub.3.4H.sub.2O) and 0.36 g of tin chloride (IV) pentahydrate
(SnCl.sub.4.5H.sub.2O) in water.
Example 2-1
ITO Film Formation
[0137] A 500 mm.times.500 mm.times.2 mm.sup.t borosilicate glass
substrate (TEMPAX #8330) was mounted on a supporting base and was
heated from room temperature until the surface temperature reached
300 to 450.degree. C. Note that the heating was provided by heat
ray heating from an infrared lamp placed above the hood in addition
to heat transfer from a heating substrate placed below the glass
substrate.
[0138] Once it was confirmed that the surface temperature of the
substrate was stable, ITO film formation was commenced.
[0139] The ITO raw material solution is sprayed in advance in a
preparation chamber so as to form mist (i.e., liquid fine
particles).
[0140] The mist conditions in the preparation chamber and on the
delivery path are shown in Table 6. Note that a bellows pipe made
from vinyl chloride that can be elongated or contracted is used for
the delivery, and water repellency was ensured by providing a
Teflon.RTM. coating on the internal wall thereof.
TABLE-US-00006 TABLE 6 Temperature of mist in preprocessing chamber
23.degree. C. Temperature of mist on delivery 23.degree. C.
Delivery path exterior temperature 22.degree. C. Proportion of
droplets in mist 1.5% by volume Flow rate of mist being transported
7,000 cm/min Length of delivery path 2.0 m
[0141] In the film formation chamber, four slit-shaped spray
nozzles (having a nozzle discharge aperture size of: 7.times.270
mm) were placed in the manner shown in FIG. 11 and the mist from
the ITO raw material solution that had been transported from the
preparation chamber was sprayed onto the substrate. At this time,
the temperature of the mist in the nozzle discharge apertures was
40.degree. C., and the mist flow rate in the nozzle discharge
apertures was 22500 cm/min.
[0142] Moreover, in order to achieve a 500 mm.times.500 mm film
formation, the distance between the spray nozzles and the glass
substrate was set to 20 mm, and any offset in the spraying density
was prevented by imparting a swing on the substrate side of .+-.150
mm in the x direction, and a swing on the nozzle side of .+-.150 mm
in the Y direction. The time required to form the Ito film was 15
minutes.
Comparative Example 2
[0143] Using circular cylinder-shaped nozzles an ITO film was
formed on a glass substrate in the same manner as in the examples
other than the nozzles were driven elliptically as is shown in
FIGS. 4A and 4B.
[0144] An ITO film was formed on a glass substrate in the above
described manner.
[0145] A comparison of the characteristics of the substrates on
which the ITO films were made in the example and the comparative
example are shown in Table 7.
TABLE-US-00007 TABLE 7 Comparative Example 2-1 Example 2 Film
thickness distribution [nm] 750 to 850 700 to 900 Sheet resistance
distribution [.OMEGA./cm.sup.2] 3.2 to 3.9 2.6 to 4.4
Transmissivity distribution [%] 80 to 83 75 to 83 (overall light
ray transmissivity)
[0146] As evident from Table 7, in the example, the in-plane
distribution of the sprayed mist quantity that was blown onto the
substrate surface was made uniform. As a result, the film thickness
and the thin film characteristics distribution were made
uniform.
Examples 2-2 to 2-4
[0147] In Examples 2-2 to 2-4, a comparison was made based on
difference in nozzle shape in slit type nozzles.
[0148] Other than the fact that nozzles having different shapes
were used, ITO films were formed on glass substrates in the same
manner as in Example 1. The three types of nozzle size and mist
spray conditions that were used in Examples 2-2 to 2-4 are shown
together in Table 8.
TABLE-US-00008 TABLE 8 Nozzle pipe inner diameter (D) [.phi.cm]
Example 2-2 Example 2-3 Example 2-4 Nozzle discharge aperture 270
.times. 7 270 .times. 9 270 .times. 7 size (X, Y) [mm] Length of
nozzle constricted 100 100 80 portion (B) [mm] Length of nozzle
parallel 100 100 80 portion (C) [mm] Formula (2) relationship Yes
No Yes Formula (3) relationship Yes Yes No Nozzle discharge
aperture 22500 17500 22500 flow rate [cm/min]
[0149] The air flow rate distribution at the discharge aperture
when air was supplied at 50,000 to 400,000 cm.sup.3/minute to each
nozzle was measured. The results thereof are shown in Table 9.
TABLE-US-00009 TABLE 9 Flow rate distribution range [cm/min] Air
flow rate [cm.sup.3/min] Example 2-2 Example 2-3 Example 2-4 50,000
.ltoreq..+-.5% .ltoreq..+-.11% .ltoreq..+-.12% 100,000
.ltoreq..+-.6% .ltoreq..+-.10% .ltoreq..+-.15% 200,000
.ltoreq..+-.3% .ltoreq..+-.13% .ltoreq..+-.16% 40,000
.ltoreq..+-.7% .ltoreq..+-.12% .ltoreq..+-.12% 60,000
.ltoreq..+-.6% .ltoreq..+-.11% .ltoreq..+-.11%
[0150] As evident from Table 9, it can be understood that the
nozzles in Example 2-2 that satisfy the relationships of both
Formula 2 and Formula 3 have a small air flow rate distribution
range and have excellent mist spray uniformity.
[0151] A comparison of the characteristics of the substrates on
which the ITO films were formed in Examples 2-2 to 2-4 are shown in
Table 10.
TABLE-US-00010 TABLE 10 Example Example Example 2-2 2-3 2-4 Film
thickness distribution [nm] 750 to 850 710 to 880 700 to 850 Sheet
resistance distribution [.OMEGA./cm.sup.2] 3.2 to 3.9 2.8 to 4.2
2.6 to 4.3 Transmissivity distribution [%] 80 to 83 76 to 83 77 to
82 (overall light ray transmissivity)
[0152] As evident from Table 10, in Example 2-2 in which nozzles
that satisfy the relationships of both Formulae (1) and (2) were
used, the distribution range of the sheet resistance was decreased
and the transmissivity was improved. This is because the
distribution range of the mist sprayed from the nozzle discharge
apertures was decreased and the film thickness distribution was
made uniform.
INDUSTRIAL APPLICABILITY
[0153] The present invention can be applied to film forming
apparatuses that form a thin film such as a transparent conductive
film or the like using spray pyrolysis deposition.
[0154] Although the above exemplary embodiments of the present
invention have been described, it will be understood by those
skilled in the art that the present invention should not be limited
to the described exemplary embodiments, but that various changes
and modifications can be made within the spirit and scope of the
present invention. Accordingly, the scope of the present invention
is not limited to the described range of the following claims.
* * * * *