U.S. patent application number 11/991474 was filed with the patent office on 2009-04-30 for film-forming material and method for predicting film-forming material.
Invention is credited to Hironori Ito, Shozo Nakayama, Tadahiro Ohmi.
Application Number | 20090110823 11/991474 |
Document ID | / |
Family ID | 37835679 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090110823 |
Kind Code |
A1 |
Ohmi; Tadahiro ; et
al. |
April 30, 2009 |
Film-forming material and method for predicting film-forming
material
Abstract
Disclosed is a method for prediction of a film material such as
a raw material for organic EL. In the method, a film material
having an evaporation rate (V(%)) represented by the formula below
can be predicted based on the values of the constant (Ko) and the
activation energy (Ea). V=(Ko/P).times.e.sup.-Ea/kT wherein Ko
represents a constant (%Torr), P represents a pressure (Torr), Ea
represents an activation energy (eV), k represents a Boltzmann
constant, and T represents an absolute temperature.
Inventors: |
Ohmi; Tadahiro; (Miyagi,
JP) ; Nakayama; Shozo; (Aichi, JP) ; Ito;
Hironori; (Aichi, JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Family ID: |
37835679 |
Appl. No.: |
11/991474 |
Filed: |
August 29, 2006 |
PCT Filed: |
August 29, 2006 |
PCT NO: |
PCT/JP2006/316925 |
371 Date: |
April 9, 2008 |
Current U.S.
Class: |
427/248.1 ;
702/22 |
Current CPC
Class: |
C23C 16/44 20130101;
C23C 14/562 20130101; H01L 51/0008 20130101; H01L 51/56 20130101;
C23C 14/228 20130101; C23C 14/56 20130101; C23C 14/243 20130101;
C23C 14/12 20130101 |
Class at
Publication: |
427/248.1 ;
702/22 |
International
Class: |
C23C 16/00 20060101
C23C016/00; G01N 31/00 20060101 G01N031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2005 |
JP |
2005-257788 |
Claims
1. A film-forming material having an evaporation rate V (%)
represented by: V=(Ko/P).times.e.sup.-Ea/kT (where Ko is a constant
(%Torr), P is a pressure (Torr), Ea is an activation energy (eV), k
is a Boltzmann constant, and T is an absolute temperature), wherein
said film-forming material is identified by a value of said
constant Ko and a value of said activation energy Ea.
2. A film-forming material according to claim 1, wherein said
activation energy Ea is obtained from a characteristic representing
a material concentration in a carrier gas when the temperature T is
changed in the state where the pressure P is constant, and said
constant Ko is determined from a specific material concentration at
a specific temperature.
3. A film-forming material according to claim 1 wherein said
constant Ko is in a range of 5.700.times.10.sup.14 (%Torr) to
6.220.times.10.sup.14 (%Torr).
4. A film-forming material according to claim 1 wherein constant Ko
is in a range of 2.600.times.10.sup.11 (%Torr) to
3.640.times.10.sup.11 (%Torr).
5. A prediction method for predicting an unknown film-forming
material, said prediction method comprising by obtaining, from a
result of measurement of a material concentration in a carrier gas,
an activation energy Ea in a formula: V=(Ko/P).times.e.sup.-Ea/kT
(where Ko is a constant (%Torr), P is a pressure (Torr), Ea is an
activation energy (eV), k is a Boltzmann constant, and T is an
absolute temperature) representing an evaporation rate V (%) of the
unknown film-forming material, and further, calculating said
constant Ko from a specific material concentration at a specific
temperature, thereby predicting the unknown film-forming material
from a value of said calculated constant Ko.
6. A film-forming material comprising an activation energy Ea and a
constant Ko satisfying a formula: V=(Ko/P).times.e.sup.-Ea/kT
(where Ko is a constant (%Torr), P is a pressure (Torr), Ea is an
activation energy (eV), k is a Boltzmann constant, and T is an
absolute temperature) representing an evaporation rate in terms of
a concentration V (%) in an atmosphere, wherein the temperature is
set to 250.degree. C. to 500.degree. C., the concentration in the
atmosphere is set to 0.1% to 10%, and the pressure is set to
10.sup.-3 Torr or more.
7. A film-forming material according to claim 6, wherein the
temperature is set to 300.degree. C. to 450.degree. C.
8. A film-forming material according to claim 6 being evaporated
and transported by a carrier gas.
9. A film forming method for evaporating the film-forming material
according to claim 6 into a carrier gas at a concentration of 0.1%
to 10% and transporting said carrier gas to the vicinity of a
substrate, thereby forming a film of said film-forming material on
said substrate.
10. An analysis method for a film-forming material that is
evaporated in evaporation means and transported to the vicinity of
a substrate by a carrier gas so as to be formed into a film on said
substrate, comprising: the method measuring a relationship between
a pressure in said evaporation means and a concentration of said
film-forming material in said carrier gas while a temperature for
evaporating said film-forming material is kept constant; making a
first judgment as to whether or not x and y are substantially in a
proportional relationship given that an inverse number of said
pressure is x and said concentration is y; measuring a relationship
between said concentration and said temperature while the pressure
in said evaporation means is kept constant; making a second
judgment as to whether or not a slope of a graph representing the
relationship between said concentration and said temperature in an
x-y plane is substantially constant regardless of said pressure
given that an inverse number of said temperature is x and a
logarithm of said concentration is y, and when said first judgment
and said second judgment are both positive, making a third judgment
based on the fact that the concentration of said film-forming
material in said carrier gas is represented by a formula:
V=(Ko/P).times.e.sup.-Ea/kT (where V is a concentration (%), Ko is
a constant (%Torr), P is a pressure (Torr), Ea is an activation
energy (eV), k is a Boltzmann constant, and T is an absolute
temperature).
11. An analysis method for a film-forming material that is
evaporated in evaporation means and transported to the vicinity of
a substrate by a carrier gas so as to be formed into a film on said
substrate, wherein, given that a concentration of said film-forming
material in said carrier gas is represented by a formula:
V=(Ko/P).times.e.sup.-Ea/kT (where V is a concentration (%), Ko is
a constant (%Torr), P is a pressure (Torr), Ea is an activation
energy (eV), k is a Boltzmann constant, and T is an absolute
temperature), the third method comprising: identifying Ea in said
formula (I) from a relationship between the temperature for
evaporating said film-forming material and said concentration while
the pressure in said evaporation means is kept constant, and
calculating Ko from a value of said Ea, the pressure in said
evaporation means, and said concentration.
12. A film forming method for evaporating a film-forming material
in evaporation means and transporting said evaporated film-forming
material to the vicinity of a substrate by a carrier gas, thereby
forming a film on said substrate, said film forming method
comprising: determining; given that a pressure in said evaporation
means is P, a temperature for evaporating said film-forming
material is T, and a concentration of said film-forming material in
said carrier gas is V, a value of one of P, T, and V based on
values of the other two and a formula: V=(Ko/P).times.e.sup.-Ea/kT
(where V is a concentration (%), Ko is a constant (%Torr), P is a
pressure (Torr), Ea is an activation energy (eV), k is a Boltzmann
constant, and T is an absolute temperature).
13. A film-forming material according to claim 2 wherein said
constant Ko is in a range of 5.700.times.10.sup.14 (%Torr) to
6.220.times.10.sup.14 (%Torr).
14. A film-forming material according to claim 2 wherein constant
Ko is in a range of 2.600.times.10.sup.11 (%Torr) to
3.640.times.10.sup.11 (%Torr).
15. A film-forming material according to claim 7 being evaporated
and transported by a carrier gas.
16. A film forming method for evaporating the film-forming material
according to claim 7 into a carrier gas at a concentration of 0.1%
to 10% and transporting said carrier gas to the vicinity of a
substrate, thereby forming a film of said film-forming material on
said substrate.
Description
TECHNICAL FIELD
[0001] This invention relates to a film-forming material that is
formed into a film by a film forming apparatus, its prediction
method and analysis method, and a film forming method.
BACKGROUND ART
[0002] A method of forming a layer of a predetermined material by
evaporating a raw material of the predetermined material is widely
used in the manufacture of semiconductor devices, flat panel
display devices, and other electronic devices. A description will
be given hereinbelow using an organic EL display device as one
example of those electronic devices. The organic EL display device
having a sufficient brightness and a lifetime of several tens of
thousands of hours or more uses an organic EL element being a
self-light-emitting element and, thus, since peripheral components
such as a backlight are small in number, it can be formed thin, and
therefore, it is ideal as a flat panel display device.
[0003] The organic EL element constituting such an organic EL
display device is required in terms of characteristics as a display
device such that, while being a large screen, the element lifetime
is long, there is no variation in luminous brightness in the screen
and element lifetime, and there is no defect such as, typically, a
dark spot. In order to satisfy such requirements, the organic EL
film forming technique is quite important.
[0004] For example, as a film forming apparatus for uniformly
forming an organic EL film on a large substrate of about 20 inches,
use is made of an apparatus described in Patent Document 1
(Japanese Unexamined Patent Application Publication (JP-A) No.
2004-79904) or the like. The film forming apparatus of Patent
Document 1 aims to achieve uniformity in film thickness on a large
substrate by optimally arranging, in a tree fashion, a piping
structure inside an injector disposed in the apparatus so as to
uniformly disperse a raw material gas on the substrate along with a
carrier gas.
[0005] Recently, an increase in size of 20 inches or more has also
been required for this type of organic EL device. However, in order
to respond to such a requirement, it is necessary to overcome
various drawbacks peculiar to the organic EL device that is poor in
light emitting efficiency and short in lifetime. Herein, since
various organic EL films, including a light emitting layer, forming
the organic EL device are as extremely thin as several tens of nm
as compared with films formed in other display devices, a technique
of forming a film on a molecular basis is required and, further, it
is also quite important to perform the film formation on the
molecular basis with high accuracy.
[0006] As a film forming apparatus also applicable to the increase
in size of 20 inches or more, the present inventors have proposed,
in Japanese Patent Application No. 2005-110760 (Prior Application
1), a film forming apparatus for uniformly and quickly forming a
film of each of various organic EL raw materials forming an organic
EL device.
[0007] The proposed film forming apparatus comprises two raw
material containers for vaporizing/evaporating the same organic EL
raw material, an ejection vessel for ejecting the organic EL raw
material onto a substrate, and a piping system (i.e. flow paths)
connecting the raw material containers and the ejection vessel to
each other. In this case, when supplying the organic EL raw
material to the ejection vessel from one of the raw material
containers, the piping system including valves and orifices is
switched in mode before the start of the film formation, at the
time of the film formation, and at the time of stopping the film
formation and the temperature of the piping system is controlled.
In this structure, during the time other than the film formation, a
gas remaining in the piping system is quickly exhausted and a gas
is circulated to the other raw material container.
[0008] In the film forming apparatus shown in Prior Application 1,
it is possible to prevent contamination due to the gas remaining in
the piping system and further to quickly perform the state
transition before the start of the film formation, at the time of
the film formation, and at the time of stopping the film formation.
Since the contamination due to the organic EL material remaining in
the piping system can be prevented, the film forming apparatus
according to Prior Application 1 can significantly improve the
brightness and lifetime of an organic EL device.
[0009] However, it has been found out that when the structure shown
in Prior Application 1 is employed, it is necessary to further
improve the use efficiency of the organic EL material forming a
light emitting layer or the like of an organic EL device and, for a
further increase in size of an organic EL device, it is necessary
to further improve the brightness of an organic EL element and to
achieve an increase in lifetime of the organic EL element.
[0010] Further, in the film forming apparatus shown in Prior
Application 1, the evaporated organic EL material is blown into the
ejection vessel from one of the raw material containers during the
film formation, but is exhausted to the exterior from the one of
the raw material containers during the time other than the film
formation. In this manner, the organic EL material is effectively
used only during the film formation but is not effectively used
during the time other than the film formation and, therefore, there
has also been found out a drawback that the use efficiency of the
using organic EL material is low.
[0011] An explanation will be given here of the characteristics and
structure of an organic EL device to be achieved. At first, the
organic EL device aimed at by this invention is an organic EL
device having a long lifetime of 10000 hours or more and a light
emitting efficiency of 100 lm/W or more. To briefly explain the
structure of the organic EL device according to this invention, it
comprises, on a glass substrate, an anode in the form of a
transparent conductive film and a cathode made of Li/Ag or the like
and provided so as to face the anode, and a plurality of layers,
for example, seven or five organic layers, disposed between the
anode and the cathode. Herein, the organic layers are, for example,
in the form of an electron injection layer, an electron transport
layer, a light emitting layer, a hole transport layer, and a hole
injection layer from the cathode side. The light emitting layer
comprises, for example, a red light emitting layer, a green light
emitting layer, and a blue light emitting layer and, by forming the
red light emitting layer, the green light emitting layer, and the
blue light emitting layer into a laminated structure in this
manner, it is possible to emit white light with high
efficiency.
[0012] Among the above organic layers, particularly the red light
emitting layer, the green light emitting layer, and the blue light
emitting layer forming the light emitting layer each have a
thickness of about 20 nm and even the electron transport layer and
the hole transport layer each have a thickness of about 50 nm. In
this manner, the organic layers of the organic EL device are
extremely thin as compared with the thicknesses of various films of
other semiconductor devices, but, for future, an attempt is made to
further reduce the thicknesses of these organic layers. In order to
deposit/form an extremely thin organic layer with high accuracy,
there is required an ultraprecise technology for forming a raw
material of an organic layer on a molecular basis. Consequently,
this means that contamination even on a molecular basis is not
allowed for formation of an organic layer. [0013] Patent Document
1: Japanese Unexamined Patent Application Publication (JP-A) No.
2004-79904
DISCLOSURE OF THE INVENTION
Subject to be Solved by the Invention
[0014] In the meantime, in the manufacture of organic EL devices
currently put to practical use, a deposition method has been used
that evaporates an organic EL material by heating it to 200 to
300.degree. C. at a pressure of 10E-4 (10.sup.-4) to 10E-5
(10.sup.-5) Torr and deposits the dispersed material onto a
substrate. In the present situation, organic EL materials used in
these organic EL devices are not fully open to the public about
their compositions, characteristics, and so on and, further, it is
difficult to analyze these organic EL materials, and therefore,
experiments and studies are conducted only relying on
specifications from the maker side. However, in the circumstances
where the organic EL materials for film formation are not specified
as described above, there are those instances where it is not
possible to judge whether or not the intended film formation has
been obtained, which thus has been a hindrance to the experiments
and studies.
[0015] Further, the situation has been such that even in the
apparatus shown in Prior Application 1 that transports an
evaporated organic EL material using a carrier gas to thereby form
a film on a substrate, no analysis is made as to what material is
suitable for the apparatus.
[0016] It is an object of this invention to provide an analysis
method for deriving from experimental data a value of a parameter
that defines a characteristic of a film-forming material, a
prediction method for predicting a film-forming material based on
this parameter, and a film forming method using this parameter.
[0017] It is another object of this invention to provide a
film-forming material determined by a value of a parameter.
Means for Solving the Subject
[0018] According to a first aspect of this invention, there is
provided a film-forming material having an evaporation rate V (%)
represented by:
V=(Ko/P).times.e.sup.-Ea/kT
[0019] (where Ko is a constant (%Torr), P is a pressure (Torr), Ea
is an activation energy (eV), k is a Boltzmann constant, and T is
an absolute temperature), said film-forming material characterized
by being identified by a value of said constant Ko and a value of
said activation energy Ea.
[0020] According to a second aspect of this invention, there is
provided a film-forming material according to the first aspect,
characterized in that said activation energy Ea is obtained from a
characteristic representing a material concentration in a carrier
gas when the temperature T is changed in the state where the
pressure P is constant, and said constant Ko is determined from a
specific material concentration at a specific temperature.
[0021] According to a third aspect of this invention, there is
provided a film-forming material according to the first or the
second aspect, characterized in that said constant Ko is in a range
of 5.700.times.10.sup.14 (%Torr) to 6.220.times.10.sup.14
(%Torr).
[0022] According to a fourth aspect of this invention, there is
provided a film-forming material according to the first or the
second aspect, characterized in that said constant Ko is in a range
of 2.600.times.10.sup.11 (%Torr) to 3.640.times.10.sup.11
(%Torr).
[0023] According to a fifth aspect of this invention, there is
provided a prediction method for predicting an unknown film-forming
material, said prediction method characterized by obtaining, from a
result of measurement of a material concentration in a carrier gas,
an activation energy Ea in a formula:
V=(Ko/P).times.e.sup.-Ea/kT
[0024] (where Ko is a constant (%Torr), P is a pressure (Torr), Ea
is an activation energy (eV), k is a Boltzmann constant, and T is
an absolute temperature) representing an evaporation rate V (%) of
the unknown film-forming material, and further, calculating said
constant Ko from a specific material concentration at a specific
temperature, thereby predicting the unknown film-forming material
from a value of said calculated constant Ko.
[0025] According to a sixth aspect of this invention, there is
provided a film-forming material characterized by having an
activation energy Ea and a constant Ko satisfying a formula:
V=(Ko/P).times.e.sup.-Ea/kT
[0026] (where Ko is a constant (%Torr), P is a pressure (Torr), Ea
is an activation energy (eV), k is a Boltzmann constant, and T is
an absolute temperature) representing an evaporation rate in terms
of a concentration V (%) in an atmosphere, wherein the temperature
is set to 250.degree. C. to 500.degree. C., the concentration in
the atmosphere is set to 0.1% to 10%, and the pressure is set to
10.sup.-3 Torr or more. Herein, the reason for setting the
temperature to 250.degree. C. or more is that the temperature is
required to be equal to or higher than a temperature necessary for
efficient evaporation of the material, and the reason for setting
the temperature to 500.degree. C. or less is that no gas
supply/control system can withstand higher temperatures. Further,
the reason for setting the concentration to 0.1% or more is that
film formation cannot be economically carried out at lower
concentrations. Preferably, the temperature is set to 300.degree.
C. to 450.degree. C.
[0027] Preferably, the above-mentioned film-forming material is
used in applications in which the material is evaporated and
transported by a carrier gas.
[0028] According to a seventh aspect of this invention, there is
provided a film forming method characterized by evaporating the
above-mentioned film-forming material into a carrier gas at a
concentration of 0.1% to 10% and transporting said carrier gas to
the vicinity of a substrate, thereby forming a film of said
film-forming material on said substrate.
[0029] According to an eighth aspect of this invention, there is
provided an analysis method for a film-forming material that is
evaporated in evaporation means and transported to the vicinity of
a substrate by a carrier gas so as to be formed into a film on said
substrate, wherein said analysis method measures a relationship
between a pressure in said evaporation means and a concentration of
said film-forming material in said carrier gas while a temperature
for evaporating said film-forming material is kept constant, and
makes a first judgment as to whether or not x and y are
substantially in a proportional relationship given that an inverse
number of said pressure is x and said concentration is y,
[0030] measures a relationship between said concentration and said
temperature while the pressure in said evaporation means is kept
constant, and makes a second judgment as to whether or not a slope
of a graph representing the relationship between said concentration
and said temperature in an x-y plane is substantially constant
regardless of said pressure given that an inverse number of said
temperature is x and a logarithm of said concentration is y, and
when said first judgment and said second judgment are both
positive, makes a judgment based on the fact that the concentration
of said film-forming material in said carrier gas is represented by
a formula:
V=(Ko/P).times.e.sup.-Ea/kT
[0031] (where V is a concentration (%), Ko is a constant (%Torr), P
is a pressure (Torr), Ea is an activation energy (eV), k is a
Boltzmann constant, and T is an absolute temperature).
[0032] According to a ninth aspect of this invention, there is
provided an analysis method for a film-forming material that is
evaporated in evaporation means and transported to the vicinity of
a substrate by a carrier gas so as to be formed into a film on said
substrate, wherein, given that a concentration of said film-forming
material in said carrier gas is represented by a formula:
V=(Ko/P).times.e.sup.-Ea/kT
[0033] (where V is a concentration (%), Ko is a constant (%Torr), P
is a pressure (Torr), Ea is an activation energy (eV), k is a
Boltzmann constant, and T is an absolute temperature),
[0034] said analysis method identifies Ea in said formula (I) from
a relationship between the temperature for evaporating said
film-forming material and said concentration while the pressure in
said evaporation means is kept constant, and calculates Ko from a
value of said Ea, the pressure in said evaporation means, and said
concentration.
[0035] According to a tenth aspect of this invention, there is
provided a film forming method for evaporating a film-forming
material in evaporation means and transporting said evaporated
film-forming material to the vicinity of a substrate by a carrier
gas, thereby forming a film on said substrate, said film forming
method characterized in that:
[0036] given that a pressure in said evaporation means is P, a
temperature for evaporating said film-forming material is T, and a
concentration of said film-forming material in said carrier gas is
V, a value of one of P, T, and V is determined based on values of
the other two and a formula:
V=(Ko/P).times.e.sup.-Ea/kT
[0037] (where V is a concentration (%), Ko is a constant (%Torr), P
is a pressure (Torr), Ea is an activation energy (eV), k is a
Boltzmann constant, and T is an absolute temperature).
[0038] Although examples of organic EL film forming apparatuses
will be described hereinbelow, it is needless to say that this
invention is not limited thereto at all and can be applied to
various film forming apparatuses.
EFFECT OF THE INVENTION
[0039] In this invention, it is possible to provide a film-forming
material suitable for film formation using a carrier gas. Further,
there are provided an analysis method for deriving from
experimental data a value of a parameter that defines a
characteristic of a film-forming material, a prediction method for
predicting a film-forming material based on this parameter, and a
film forming method using this parameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a schematic structural diagram showing one example
of a film forming apparatus suitable for film formation using a
material of this invention.
[0041] FIG. 2 is a schematic structural diagram showing another
example of a film forming apparatus suitable for film formation
using a material of this invention.
[0042] FIG. 3 is a diagram for more specifically explaining a
piping system, a switcher, and a film forming section of the film
forming apparatus shown in FIG. 1 or 2.
[0043] FIG. 4 is a perspective view showing a main portion of still
another example of a film forming apparatus suitable for film
formation using materials of this invention.
[0044] FIG. 5 is a diagram showing a film forming section of the
film forming apparatus of FIG. 4.
[0045] FIG. 6 is a timing chart showing switching timings and so on
in the film forming apparatus of FIG. 4.
[0046] FIG. 7 is a diagram showing experimental results when a
material according to this invention was used.
[0047] FIG. 8 is a diagram showing the temperature dependence of
evaporation behavior of an organic EL raw material (material H)
according to this invention, wherein there is shown the temperature
dependence in the state where the pressure is kept constant.
[0048] FIG. 9 is a diagram showing the pressure dependence of
evaporation behavior of an organic EL raw material (material H)
according to this invention, wherein there is shown the pressure
dependence in the state where the temperature is kept constant.
[0049] FIG. 10 is a diagram showing the characteristics when a
material according to this invention was used, wherein the pressure
dependence of the concentration of an organic EL raw material
(material H) in a carrier gas is shown in relation to
temperature.
[0050] FIG. 11 is a diagram showing, like FIG. 10, the
characteristics when a material according to this invention was
used, wherein the temperature dependence of the concentration of an
organic EL raw material (material H) in a carrier gas is shown in
relation to pressure.
[0051] FIG. 12 is a diagram showing the pressure dependence of
evaporation behavior of an organic EL raw material (material C)
according to this invention, wherein there is shown the pressure
dependence in the state where the temperature is kept constant.
[0052] FIG. 13 is a diagram showing the characteristics of a
material according to this invention, wherein the pressure
dependence of the concentration of an organic EL raw material
(material C) in a carrier gas is shown in relation to
temperature.
[0053] FIG. 14 is a diagram showing, like FIG. 13, the
characteristics of a raw material according to this invention,
wherein the temperature dependence of the concentration of an
organic EL raw material (material C) in a carrier gas is shown in
relation to pressure.
BEST MODE FOR CARRYING OUT THE INVENTION
[0054] Referring to FIG. 1, a film forming apparatus according to a
first embodiment of this invention is schematically illustrated.
The illustrated film forming apparatus comprises an organic EL
source section 20 having a plurality of organic EL sources, first
and second film forming sections 26 and 27, and a switching section
29 (switching means) for supplying an evaporated organic EL
material from the organic EL source section 20 selectively to the
first and second film forming sections 26 and 27. The switching
section 29 comprises piping, orifices, mass controllers (flow
control systems), valves, and so on. In this connection, the
switching section 29 is controlled by a controller (not shown) that
controls the valves, the orifices, the flow control systems, and
the valves.
[0055] Specifically, the illustrated organic EL source section 20
has container sections (hereinafter referred to as raw material
container sections) containing organic EL raw materials
corresponding to the number of organic EL films to be deposited.
For example, in the case of three kinds of organic EL raw materials
to be deposited on a glass substrate, the organic EL source section
20 includes three raw material container sections containing the
three kinds of organic EL raw materials, respectively. In the case
of depositing more kinds of organic EL raw materials, there are
provided raw material container sections, containing the organic EL
raw materials, corresponding to the number of those raw materials.
For example, in the case where organic EL films to be deposited are
six layers including an electron transport layer, a red light
emitting layer, a green light emitting layer, a blue light emitting
layer, an electron blocking layer, and a hole transport layer, six
raw material container sections containing raw materials for
forming the respective layers are provided in the organic EL source
section 20.
[0056] Further, in each raw material container section 201 of the
organic EL source section 20, there are provided not only an
evaporating jig (i.e. an evaporating dish) containing the organic
EL raw material for evaporation thereof, but also a heater for
heating the organic EL material in the evaporating jig. A carrier
gas such as argon, xenon, or krypton is introduced into the
evaporating jig of each raw material container section 201 through
valves, a flow control system, and a piping system.
[0057] Herein, in each raw material container section 201, the
carrier gas is introduced and heating is carried out by the heater
and, as a result of this, the organic EL material in the
evaporating jig is evaporated. Therefore, each raw material
container section 201 has a function as evaporation means for
evaporating the organic EL material. In the figure, only the single
raw material container section 201 is shown in the organic EL
source section 20 for simplification of description, but the
organic EL source section 20 is further provided with the raw
material container sections corresponding to the other organic EL
raw materials. In this manner, each raw material container section
operates as evaporation means for evaporating the organic EL raw
material.
[0058] On the other hand, the switching section 29 is provided
corresponding to the illustrated raw material container section 201
and, although the same switching sections are provided for the
other raw material container sections, respectively, illustration
thereof is omitted here for simplification. Carrier gas piping
systems 31 (piping, valves, flow control systems, orifices, etc)
each for supplying a gas of the same kind as the carrier gas such
as argon, xenon, or krypton to the switcher 29 are connected to the
switching section 29 and, herein, are provided in one-to-one
correspondence with the first and second film forming sections 26
and 27. This carrier gas piping system 31 is operated as carrier
gas supply means for supplying the carrier gas to gas ejection
means not through the evaporation means.
[0059] The illustrated switching section 29 comprises a piping
system including therein piping, valves, orifices, flow control
systems, and so on and supplies the carrier gas and the evaporated
organic EL raw material selectively to the first and second film
forming sections 26 and 27.
[0060] The first and second film forming sections 26 and 27 have
the same structure as each other and, as will be described later,
are respectively connected to the switcher 29 through piping
systems 331 and 332 having portions with the same piping path
length as each other. A description will be given assuming that the
illustrated first and second film forming sections 26 and 27 eject
and deposit an organic EL raw material evaporated in the
illustrated raw material container section 201. However, when
depositing a plurality of organic EL raw materials in the first and
second film forming sections 26 and 27, respectively, it is
actually necessary to provide a plurality of switchers between a
plurality of raw material container sections and the first and
second film forming sections 26 and 27 and to provide piping
systems (gas flow paths) for connection between the plurality of
raw material container sections and the first and second film
forming sections 26 and 27 through those switchers.
[0061] Each of the first and second film forming sections 26 and 27
comprises an ejection vessel configured to uniformly eject a
carrier gas containing the evaporated organic EL raw material onto
a glass substrate and a conveyor for conveying the glass substrate
on a stage maintained at a constant temperature and operates to
eject the carrier gas containing the evaporated organic EL raw
material onto the glass substrate from the ejection vessel to
thereby deposit an organic EL film thereon. Therefore, the ejection
vessel can be called gas ejection means. As is also clear from
this, the illustrated film forming apparatus has a plurality of gas
ejection means for one evaporation means.
[0062] The ejection vessel comprises supply ports arranged such
that the organic EL material from the piping system 331, 332 is
uniformly dispersed, and a filter for guiding the organic EL
material to the glass substrate or the like. The filter may be
replaced with a shower plate in the form of a ceramic or metal
plate formed with fine holes.
[0063] Hereinbelow, the operation of the film forming apparatus
shown in FIG. 1 will be described. At first, an organic EL raw
material (organic EL molecules) is evaporated by heating at the raw
material container section 201. In this state, when the first film
forming section 26 is selected by the switching section 29, the
organic EL material from the raw material container section 201 is
supplied to the first film forming section 26 through the piping
system of the switching section 29 and through the piping system
331 in the evaporated state along with the carrier gas. While the
organic EL raw material is supplied to the first film forming
section 26, the piping system 332 connected to the second film
forming section 27 is closed. While film formation is performed in
the first film forming section 26, a glass substrate is supplied to
an inlet of the second film forming section 27 so that the second
film forming section 27 is in a film formation standby state.
[0064] When deposition of the organic EL raw material is finished
in the first film forming section 26, the organic EL raw material
from the raw material container section 201 is supplied to the
second film forming section 27 through the piping system 332 due to
switching of the piping system by the switcher 29. While film
formation is performed in the second film forming section 27, the
glass substrate finished with the film formation in the first film
forming section 26 is guided by the conveyor to another ejection
vessel provided in the first film forming section 26 for forming a
film of another organic EL raw material, so that the film formation
is carried out using this other organic EL raw material. In other
words, different substrates are supplied at different timings to a
plurality of gas ejection means corresponding to one evaporation
means.
[0065] Subsequently, in the same manner as described above, the
first and second film forming sections 26 and 27 are controlled to
be switched therebetween at the timings determined by the switcher
29 and organic EL raw materials to be deposited are switched in
order, so that organic EL films necessary for an organic EL device
are deposited on each of the glass substrates moving in
parallel.
[0066] Herein, the piping system 332 between the switcher 29 and
the second film forming section 27 has a length equal to that of
the piping system 331 between the switcher 29 and the first film
forming section 26 and a piping tree is formed so that film
formation is performed under the same conditions. Further, the
piping systems 331 and 332 are controlled so that the organic EL
raw material is supplied to the first and second film forming
sections 26 and 27 at the same flow rate. As a result of this, in
the first and second film forming sections 26 and 27, film
formation of the same organic EL raw material is selectively
carried out under the same conditions.
[0067] Therefore, according to this structure, when film formation
is finished in one of the film forming sections 26 and 27, film
formation can also be performed in the other of the film forming
sections 26 and 27 under entirely the same conditions. Further,
while a glass substrate finished with film formation is moving in
one of the film forming sections 26 and 27, switching is made to
the other of the film forming sections 26 and 27 so that the
organic EL raw material is supplied to the film forming section
after the switching under the same conditions as the one of the
film forming sections. Accordingly, the film forming apparatus
shown in FIG. 1 can form in order organic EL material films on a
plurality of glass substrates in a simultaneous parallel fashion
and utilize the organic EL raw material from the raw material
container section 201 without waste, thus making it possible to
largely improve the use efficiency of the organic EL raw
material.
[0068] Referring to FIG. 2, there is shown a conceptual diagram of
a film forming apparatus according to a second embodiment of this
invention. The illustrated example differs from the film forming
apparatus of FIG. 1 in that an organic EL raw material from an
organic EL source section 20 is individually supplied to three film
forming sections, i.e. first to third film forming sections 26 to
28, through a switcher 29, while it is supplied only to the two
film forming sections 26 and 27 in the film forming apparatus of
FIG. 1. In the illustrated example, the third film forming section
is connected to the switcher 29 through a piping system 333 and the
piping system 333 is controlled in the same manner as the other
piping systems 331 and 332.
[0069] At any rate, in the film forming apparatus shown in FIG. 2,
an evaporated organic EL raw material from each raw material
container section 201 is selectively supplied to the first to third
film forming sections 26 to 28 through a switcher 29.
[0070] Referring to FIG. 3, there is shown a portion of the film
forming apparatus shown in FIG. 1 or 2, wherein the connection
relationship among the organic EL source section 20, the switcher
29, and the single film forming section 26 is shown along with a
partial structure of the inside of the film forming section 26. The
film forming section 26 shown in FIG. 3 comprises an ejection
vessel 261 for ejecting a carrier gas containing an organic EL raw
material (molecules) in the film forming section 26 and a stage 262
supporting a glass substrate 30. In the state where the glass
substrate 30 is mounted thereon, the stage 262 is movable, for
example, in a direction perpendicular to the sheet surface of FIG.
3. Further, inside the ejection vessel 261, gas dispersion plates
263 are provided in the number of six in this example and a filter
264 (or a shower plate) made of metal or ceramic is disposed at a
position facing the glass substrate 30. Supply ports are provided
corresponding to the gas dispersion plates and both are arranged in
a row in the same direction (vertical direction on the sheet
surface of FIG. 3). The filter 264 has a shape extending in the
arranging direction of the supply ports and the gas dispersion
plates. The inside of the illustrated film forming section 26 is
maintained at a pressure of about 5 to 30 mTorr and the stage 262
is maintained at room temperature.
[0071] Herein, the filter 264 is preferably made of a porous
ceramic. Generally, when the filter 264 made of the porous ceramic
is used, a fluid in the form of a gas or a liquid can be uniformly
supplied onto a large-area substrate at a predetermined angle.
[0072] On the other hand, the illustrated organic EL source 20 is
featured by a single raw material container section 201, wherein
the illustrated raw material container section 201 is connected to
upstream piping and downstream piping. The upstream piping is
piping for introducing a carrier gas into the raw material
container section 201 and, as illustrated, includes a flow control
system (FCS1) and valves V3 and V4 provided before and after the
flow control system FCS1. The downstream piping forms part of the
switcher 29.
[0073] The raw material container section 201 is divided into an
upstream region and a downstream region by a vertically extending
partition 202 and an evaporating portion 203 filled with an organic
EL raw material is provided under the partition 202. Further, as
described before, the raw material container section 201 is
provided with a heater (not shown).
[0074] In this structure, the carrier gas introduced through the
upstream piping is led into the evaporating portion 203 through the
upstream region of the raw material container section 201, so that
the organic EL raw material (molecules) evaporated in the
evaporating portion 203 due to heating by the heater is, along with
the carrier gas, led out into the downstream piping through the
downstream region of the raw material container section 201.
[0075] Like in FIGS. 1 and 2, the switcher 29 is connected to the
raw material container section 201. The switcher 29 shown in FIG. 3
comprises a piping system establishing connection between the
plurality of film forming sections 26, 27, etc. and the organic EL
source section 20 (i.e. the raw material container section 201) and
a piping system for supplying a carrier gas to the film forming
section 26.
[0076] Specifically, a piping system of the switcher 29
establishing connection between the raw material container section
201 and the ejection vessel 261 of the film forming section 26
comprises a first piping system including valves V5 and V6 and an
orifice ORF1 and extending to the supply ports corresponding to the
four gas dispersion plates 263 provided in the ejection vessel 261
and a second piping system directly leading an externally provided
carrier gas source (not shown) of xenon, argon, or the like to the
two gas dispersion plates 263 of the ejection vessel 261. The
second piping system reaches the supply ports corresponding to the
gas dispersion plates 263 of the ejection vessel 261 through a
valve V1, a flow control system FCS2, and an orifice ORF2. Further,
a third piping system for introducing a gas of the same kind as the
carrier gas from the exterior is connected to the first piping
system between the orifice ORF1 and the valve V6. This third piping
system includes a valve V2, a flow control system FCS3, and a valve
V7. Further, a fourth piping system for supplying the evaporated
organic EL raw material to another film forming section (e.g. 27 in
FIG. 1) is connected to the first piping system between the valves
V5 and V6. This fourth piping system includes a valve V8. Each of
the orifices ORF1, 2, and 3 illustrated in the figure is operated
as a gas pressure adjusting portion having an orifice and a valve
for adjusting/controlling a gas pressure. Therefore, it is
understood that the illustrated film forming apparatus has a
structure such that the gas pressure adjusting portion is provided
between the evaporation means and the ejection vessel, and the gas
pressure adjusting portion and the supply ports of the ejection
vessel are connected to each other by the piping.
[0077] Herein, if, in the first piping system for supplying the
carrier gas containing the organic EL raw material (molecules) to
the ejection vessel 261, the lengths of the piping between the
orifice ORF1 and the supply ports of the ejection vessel 261 are
all set equal to each other, it is possible to supply the organic
EL raw material (molecular gas) so as to reach the glass substrate
30 uniformly and simultaneously. In this connection, in the
illustrated example, the number of the organic EL molecular gas
supply ports in the ejection vessel 261 is set to 2.sup.n, and
these supply ports and the orifice ORF1 are connected to each other
by the piping branched into 2.sup.n paths (n is a natural number).
Further, by providing the same piping between the orifice ORF1 and
the supply ports of the ejection vessel 261 in each of the
plurality of film forming sections, it is possible to uniformly
form films of the same organic EL material under the same
conditions in the plurality of film forming sections.
[0078] Only the carrier gas is supplied to the gas dispersion
plates 263 provided at both upper and lower ends in FIG. 3.
[0079] Further, the temperature of the first piping system from the
raw material container section 201 to the ejection vessel 261 is
set higher than the temperature of the raw material container
section 201 supplying the organic EL raw material, so as to prevent
deposition/adsorption of the organic EL raw material (molecules) on
the walls of pipes forming the piping system.
[0080] Herein, referring to FIGS. 1 and 3, the operation of the
film forming apparatus will be described. At first, the operation
of the illustrated film forming apparatus can be classified into
operations before the start of film formation, during the film
formation, and at the time of stopping the film formation for each
of the film forming sections 26 and 27. Herein, a description will
be made on the assumption that the operations before the start of
the film formation, during the film formation, and at the time of
stopping the film formation are a mode 1, a mode 2, and a mode 3,
respectively.
[0081] In the mode 1 before the start of the film formation for the
film forming section 26, the valves V1, V2, V3, V4, and V7 are in
the open state, the valve V6 is in the closed state, and the valves
V5 and V8 are in the open state. Accordingly, in the mode 1, the
carrier gas is supplied into the ejection vessel 261 through the
valve V1, the flow control system FCS1, and the orifice ORF2, while
the carrier gas flows into the ejection vessel 261 through the
valve V2, the flow control system FCS3, the valve V7, and the
orifice ORF1. In this state, the pressure in the ejection vessel
261 and the pressure on the glass substrate 30 are controlled at
predetermined pressures. In this case, for example, the pressure in
the ejection vessel 261 is controlled at 10 Torr and the pressure
on the glass substrate is controlled at 1 mTorr.
[0082] Further, in the state of the mode 1, since the valves V3 and
V4 are in the open state, the carrier gas to be introduced into the
raw material container section 201 that supplies the organic EL
molecules is introduced into the raw material container section 201
through the path of the valve V3, the flow control system FCS1, and
the valve V4 and, since the valve V6 is in the closed state, the
organic EL raw material is not fed to the film forming section 26
but is supplied to the other film forming section (e.g. 27) through
the valves V5 and V8 in the open state. Naturally, in a mode before
the start of the film formation for the entire film forming
apparatus, the valves V5 and V8 are also set to the closed state
and, therefore, the organic EL raw material is not fed to either of
the film forming sections 26 and 27 from the raw material container
section 201 and only the gas of the same kind as the carrier gas is
fed thereto through the piping systems provided for both film
forming sections, respectively.
[0083] In FIG. 3, at the start of the film formation, the state of
the first film forming portion 26 is shifted from the mode 1 to the
mode 2 during the film formation. In the mode 2 during the film
formation, the valves V2, V7, and V8 are set to the closed state,
while, the valves V1, V3, V4, V5, and V6 are set to the open state.
As a result of this, the carrier gas is fed to the upper and lower
supply ports of the ejection 261 through V1, the flow control
system FCS2, and the orifice ORF2 and, further, the organic EL
molecular gas evaporated in the raw material container section 201
is supplied to the four supply ports of the ejection vessel 261
through the path of V5, V6, and the orifice ORF1 by the carrier gas
introduced through the path of the valve V3, the flow control
system FCS1, and the valve V4.
[0084] In this mode 2, the gas (flow rate f1) of the same kind as
the carrier gas that was supplied through the valve V2, the flow
control system FCS3, the valve V7, and the orifice ORF1 is stopped.
On the other hand, in order to keep constant the pressure in the
ejection vessel 261 and the pressure in a chamber, it is preferable
that the carrier gas flow rate from the raw material container
section 201 serving to supply the organic EL molecules to the
ejection vessel 261 be, in principle, set equal to the foregoing
flow rate f1. That is, the transport gas flow rate in the path of
the valves V5 and V6 and the orifice ORF1 is preferably equal to
the flow rate f1 of the gas of the same kind as the carrier gas
that was fed in the path of the valve V2, the flow control system
FCS3, the valve V7, and the orifice ORF1 in the mode 1.
[0085] Next, referring to FIG. 3, the mode 3 at the time of
stopping the film formation for the first film forming section 26
will be described. When shifting from the state of the mode 2 to
the state of the mode 3, the valve V6 is set to the closed state
and the valves V5 and V8 are set to the open state and,
simultaneously, the valves V2 and V7 are set to the open state.
That is, in the mode 3, the valves V1, V2, V3, V4, V5, V7, and V8
are set to the open state, while, the valve V6 is set to the closed
state, so that the organic EL raw material from the raw material
container section 201 is supplied to the other film forming section
(e.g. 27).
[0086] In this manner, in the mode 3, since the valves V5 and V8
are set to the open state, the carrier gas containing the organic
EL molecules flows from the raw material container section 201 side
to the other film forming section at the flow rate f1 in the mode
2. On the other hand, since the valves V2 and V7 are set to the
open state, the gas of the same kind as the carrier gas flows into
the ejection vessel 261 of the first film forming section 26
through the orifice ORF1 at the flow rate f1 equal to that in the
mode 1. By this gas of the same kind as the carrier gas, the
organic EL molecules in the piping from the valve V6, which was in
the open state in the mode 2, to the ejection vessel 261 are blown
off. Therefore, the expelling of the organic EL molecules is
extremely fast in the film forming section 26 at the time of
stopping the film formation.
[0087] FIG. 4 is a perspective view of a main portion of a film
forming system according to another embodiment of this invention.
In this embodiment, a film forming section comprises two film
forming sections like in the first embodiment, wherein each of the
film forming sections 26 and 27 has six ejection vessels. In FIG.
4, the same reference numerals are assigned to portions
corresponding to those in the embodiment of FIGS. 1 and 3. The film
forming section will be described in detail with reference to FIG.
5. As shown in FIG. 4, in a first film forming section array
(chamber CHM1), six ejection vessels each extending to have a
length equal to the width of a glass substrate are aligned adjacent
to each other to be in parallel to each other in their length
directions. A glass substrate 30 moves at a predetermined speed
over the group of ejection vessels in a direction crossing the
above length direction. A second film forming section array
(chamber CHM2) is configured in the same manner and another glass
substrate 30 is supplied thereover at a timing different from that
over the first array. The ejection vessels disposed in the two
arrays form pairs and a carrier gas containing a raw material is
supplied to each pair at different timings from the same raw
material container section. When the carrier gas containing the raw
material is selectively supplied to one of the pair of ejection
vessels, the glass substrate is present thereover, while, during
that time, the carrier gas containing the raw material is not
supplied to the other of the pair of ejection vessels and the glass
substrate is also not present thereover. Supply/movement of the
glass substrates and selection as to which of the pair of ejection
vessels the carrier gas containing the raw material is supplied to
are cooperatively performed to determine the timing so that the
carrier gas containing the raw material is always supplied to
either of the pair and the substrate is present thereover.
[0088] Referring to FIG. 5, the single film forming section array
(chamber) of the film forming system according to the embodiment of
FIG. 4 will be described. FIG. 5 shows the single film forming
section array for use in manufacturing an organic EL device by
forming organic EL films in sequence on a substrate 30 of glass or
the like, wherein the films of six layers are formed in sequence on
the substrate. In this case, use can be made of a substrate with a
size from 730.times.920 (mm) to 3000.times.5000 (mm).
[0089] The illustrated film forming section array comprises six
ejection vessels 26-1 to 26-6 separated by partitions 1 to 7,
wherein the ejection vessels eject carrier gases containing organic
EL materials onto the glass substrate located above in the order of
stacking of the films. These six ejection vessels 26-1 to 26-6 are
aligned so that the extending directions of internal filters or
shower plates are parallel to each other with respect to the
conveying direction of the glass substrates. Glass substrates 30-1
and 30-2 move, with a fixed interval therebetween, over the six
ejection vessels from left to right in the figure and are subjected
to formation of organic EL films by the organic EL raw materials
ejected upward in the figure from respective ejecting portions of
the ejection vessels 26-1 to 26-6. In this event, predetermined
distances are maintained between the substrate 30-1, 30-2 and each
partition and between the substrate 30-1, 30-2 and each of the
ejection vessels 26-1 to 26-6, wherein the distance between the
substrate 30-1, 30-2 and each partition is smaller than the
distance between the substrate 30-1, 30-2 and each of the ejection
vessels 26-1 to 26-6. The gases ejected upward from the respective
ejection vessels pass through spaces between the side walls of the
ejection vessels and the inner surfaces of the partitions so as to
be exhausted downward as shown by arrows. The piping system as
shown in FIGS. 3 and 4 is connected to each of the ejection
vessels. Therefore, the film forming section array (chamber) shown
in FIG. 5 is connected to the non-illustrated other film forming
section array (chamber) through the respective piping systems. By
controlling the respective piping systems of the plurality of film
forming section arrays by respective switchers, it is possible to
parallelly process glass substrates in two rows.
[0090] In the embodiment of FIG. 5, the glass substrate 30-1, 30-2
has a size of 2,160 mm.times.2,540 mm and moves in its longitudinal
direction. The width of an ejection port of each ejection vessel in
the glass substrate moving direction is 50 mm, the length of the
ejection port perpendicular thereto is 2,170 mm, the width
(thickness) of the side wall of each ejection vessel is 15 mm, the
distance between the outer surface of the side wall of each
ejection vessel and the inner surface of each of the partitions on
both sides thereof is 30 mm, thus the distance between the inner
surfaces of the adjacent partitions is 140 mm, the thickness of
each partition is 15 mm, and the length of the film forming section
array (chamber) in the substrate moving direction is 945 mm. The
distance between the upper surface of each ejection vessel and the
substrate is 20 mm, the distance between each partition and the
substrate is 2 mm, and the temperature of each partition and each
ejection vessel is set to 350 to 450.degree. C. The pressure of a
film forming atmosphere is 30 mTorr and the ejection speed of the
carrier gas containing the raw material ejected from the ejecting
portion is 3 m/sec, so that the carrier gas containing the raw
material reaches the substrate in 0.1 seconds. The ejection flow
rate of the carrier gas containing the raw material from each
ejection vessel is 317 cc/min in terms of room temperature and the
atmospheric pressure. Assuming that the substrate feed speed is 1.0
cm/sec, the time required for the substrate to pass through one
ejection vessel is 264 seconds and the time required for the
substrate to pass through six ejection vessels is 341.5 seconds.
The use efficiency of the organic EL raw materials reaches 90%.
[0091] Referring here to FIG. 6, an upper chart is a timing chart
showing a switching cycle between the ejection vessels in pairs
arranged separately in the two film forming section arrays
(chambers), wherein each ejection vessel is subjected to switching
of gas supply per 264 seconds. A lower timing chart shows a cycle
of the operation in each chamber, wherein, in each chamber, film
formation of six layers is achieved in 341.5 seconds and, for 186.5
seconds thereafter, feed-out of a substrate finished with the film
formation from the chamber and introduction of a new substrate into
the chamber are carried out, so that one cycle is finished in 528
seconds in total. In this one cycle of 528 seconds (8 minutes and
38 seconds), the film formation of 6 layers on the two substrates
is completed.
[0092] Referring back to FIGS. 3 to 5, all the ejection vessels are
made to have completely the same structure, the same piping system
described with reference to FIG. 3 is connected to each of them,
and the flow rates of the carrier gas to be supplied thereto are
also set to the same value. In this case, the temperature of each
ejection vessel may be set so as to match the properties of the
organic EL molecules. The film forming rate/thickness is preferably
controlled by the temperature of each raw material container
section. Further, each ejection vessel is preferably made of a
stainless steel and the ejecting portion of each ejection vessel is
in the form of a stainless filter and is welded to the body. All
the inner surfaces of each ejection vessel are preferably coated
with a passive film of Al.sub.2O.sub.3 or the like having a low
catalytic effect.
[0093] Further, in the film forming apparatus according to this
invention having the plurality of film forming sections and
carrying out the control as described with reference to FIG. 3, the
carrier gas flows into the respective film forming sections at
completely the same flow rate in either of the modes during the
film formation and at the time of stopping the film formation and,
therefore, the pressure in the respective ejection vessels forming
the respective film forming sections can be maintained constant.
This means that cross contamination between the ejection vessels
can be prevented.
[0094] In the case where the ejection vessels for six layers all
have the same size and the flow rates of a carrier gas to be
ejected are set to the same value, the concentrations of organic EL
raw material molecules in the carrier gas may be set to the same
value when the required thicknesses of the respective layers are
the same (red light emitting layer, green light emitting layer,
blue light emitting layer, electron blocking layer: thickness is 20
to 10 nm for each), while, with respect to the layers with a larger
thickness (electron transport layer, hole transport layer:
thickness is 50 nm for each), it is necessary to increase the
concentration of organic raw material molecules contained in the
carrier gas in proportion to the thickness. If this is difficult,
it is necessary to take a measure for the layer with the larger
thickness to use a plurality of ejection vessels, to increase the
opening width of the ejection vessel, to increase the flow rate of
the carrier gas, or the like.
[0095] Further, as described before, by providing the plurality of
film forming sections and temporally switching the modes of these
plurality of film forming sections, it is possible to quickly form
a plurality of films necessary for an organic EL device and thus to
largely improve the throughput and also improve the use efficiency
of the organic EL raw materials. For example, in the case of
manufacturing an organic EL device by forming organic EL material
films of six layers by switching three film forming sections,
organic EL devices can be manufactured at intervals of about 6
minutes and, in this case, the use efficiency of the organic EL raw
materials can be improved to 82%. As shown in FIGS. 4 to 6, in the
case of performing the film formation using the two film forming
section arrays, the 6-layer film formation is enabled at intervals
of about 8 minutes and the material use efficiency reaches 90%.
[0096] Herein, in order to manufacture an organic EL device having
the intended characteristics, it is extremely important to keep
constant the concentration, in a carrier gas, of an organic EL raw
material evaporated from each raw material container section. In
other words, if the concentration of the organic EL raw material in
the carrier gas changes in a short time, it is impossible to
uniformly deposit the organic EL material on a glass substrate or
the like on a molecular basis over a long period of time.
[0097] When the concentration of an organic EL raw material in a
carrier gas is constant, the required concentration is determined
as follows. At first, assuming that the molecular weight of organic
EL materials of six layers is 500, a molecular layer of each
material film has a thickness of 0.7 nm and the number of molecules
is 2.0.times.10E14 (10.sup.14) per cm.sup.2. Assuming that the
thickness of each of a red light emitting layer, a green light
emitting layer, a blue light emitting layer, and an electron
blocking layer is 20 nm, the number of molecules of the material
required for each layer is about 6.times.10E15 (10.sup.15) per
cm.sup.2. Since the thickness of each of an electron transport
layer and a hole transport layer is 50 nm, 1.4.times.10E16
(10.sup.16) molecules are required per cm.sup.2 for each layer.
Assuming that the density of a carrier gas flow sprayed onto a
glass substrate is 2.58.times.10E-3 (10.sup.-3) cc/sec per
cm.sup.2, the number density of a gas sprayed onto the surface of
the glass substrate is 6.96.times.10E16 (10.sup.16) molecules/sec
per cm.sup.2. In the foregoing example, since the glass substrate
passes over the ejection port with the width of 5 cm at the speed
of 1.0 cm/sec, the gas is sprayed onto the respective portions of
the substrate for 5 seconds and the number of gas molecules in the
carrier gas containing the organic EL molecules for 5 seconds
becomes 3.48.times.10E17 (10.sup.17) per cm.sup.2. Since about
6.times.10E15 (10.sup.15) organic EL molecules per cm.sup.2 should
be contained in this gas flow in the case of each of the red light
emitting layer, the green light emitting layer, the blue light
emitting layer, and the electron blocking layer and 1.4.times.10E16
(10.sup.16) organic EL molecules per cm.sup.2 should be contained
in this gas flow in the case of each of the electron transport
layer and the hole transport layer, it is necessary to set the
concentration of the organic EL raw material molecules contained in
the carrier gas to about 1.7% for each of the red light emitting
layer, the green light emitting layer, the blue light emitting
layer, and the electron blocking layer and to about 4% for each of
the electron transport layer and the hole transport layer. These
concentrations are fully achievable by heating the respective
materials at temperatures of 500.degree. C. or less. This
concentration required for each layer can be set to a different
value by changing the speed, flow rate, and density of the carrier
gas flow sprayed onto the glass substrate, the moving speed of the
glass substrate, the opening width of the ejecting portion, and so
on. Further, the concentration of the organic EL raw material
molecules in the carrier gas can be controlled by the heating
temperature used for evaporating the material, the pressure at the
evaporating portion, and so on.
[0098] As a result of this, according to the present film forming
system, it is possible to control the film formation with a
predetermined thickness quite accurately and at high speed.
[0099] Referring to FIG. 7, the concentration is shown in the case
where Ar was used as a carrier gas and use was made of an organic
EL raw material known as a material H.
[0100] In FIG. 7, a curve C1 shows changes in concentration (left
scale) of the material H in the carrier gas when 200 mg of the
material H was filled in an evaporating dish, maintained at a
temperature of 250.degree. C. for 5 minutes, and then heated to
470.degree. C. (right scale) so as to be evaporated. Further, the
experiment was conducted by disposing the evaporating dish in a raw
material container section maintained at a pressure of 75 Torr and
supplying the carrier gas at a flow rate of 10 sccm into the raw
material container section. Herein, it is shown that the
concentration can be maintained at 9000 ppm or more for 100 minutes
or more. Accordingly, an extremely thin film of the material H can
be uniformly formed over a long period of time in a film forming
apparatus.
[0101] FIG. 8 shows the temperature dependence of evaporation
behavior of the organic EL raw material (herein, the material H),
wherein there are shown changes in concentration of the material H
when the temperature for evaporation of the material H was changed
in the range of 430.degree. C. to 450.degree. C. in the state where
the pressure of raw material container sections was maintained
constant (e.g. at 30 Torr). In this example, there is shown the
case where 200 mg of the material H was filled in each of
evaporating dishes and the carrier gas was supplied at a flow rate
of 10 sccm. A curve C3 shown in FIG. 8 shows a characteristic when
the evaporating dish was heated at 430.degree. C. in the state
where the pressure was maintained at 30 Torr, wherein the
concentration can be maintained substantially constant at about
5000 ppm over a long period of time, i.e. until the filled organic
EL raw material is exhausted.
[0102] On the other hand, a curve C4 shows concentration changes
when heated at 440.degree. C. in the state where the pressure was
maintained at 30 Torr. Also in this case, it is possible to
maintain a concentration of 9000 ppm for 2 hours or more. Further,
a curve C5 shows concentration changes when heated at 450.degree.
C. in the state where the pressure was maintained at 30 Torr,
wherein a concentration of 13000 ppm can be achieved and this
concentration can be maintained until substantially all the filled
organic EL raw material is evaporated from the evaporating
dish.
[0103] Referring to FIG. 9, there are shown the pressure dependence
characteristics of evaporation behavior of the material H being the
organic EL raw material. In this example, evaporating dishes are
maintained at a temperature of 440.degree. C. and Ar is supplied as
a carrier gas to the evaporating dishes at a flow rate of 10 sccm.
Like in FIGS. 7 and 8, 200 mg of the material H is filled in each
evaporating dish. Curves C6, C7, and C8 show evaporation
characteristics of the material H in the states where raw material
container sections (atmospheres of the evaporating dishes) were
maintained at 75 Torr, 30 Torr, and 20 Torr, respectively. As is
also clear from these curves C6 to C8, the concentration of the
material H in the carrier gas increases as the pressure decreases
and, in any of the cases, the concentration of the material H in
the carrier gas can be maintained substantially constant.
[0104] Referring to FIG. 10, there is shown the relationship
between concentration and pressure in the state where the
temperature of each evaporating dish was maintained constant. In
FIG. 10, for reference, the upper scale is graduated in Torr and
the lower scale is graduated in 1/P (1/Torr). In FIG. 10, a
characteristic C9 represents the relationship between the pressure
and the concentration of the material H in the carrier gas when the
material H was heated at 430.degree. C. and, likewise,
characteristics C10 and C11 represent the characteristics when the
material H was heated at 440.degree. C. and 460.degree. C.,
respectively. Herein, given that the concentration on the axis of
ordinates is y and (1/P) of the lower scale of the axis of
abscissas is x in FIG. 10, the characteristic C9 can be
approximated by a straight line of y=16.991x-0.0264 and, likewise,
the characteristics C10 and C11 can be approximated by straight
lines of y=24.943x+0.1053 and y=59.833x+0.0314, respectively. With
respect to any of the temperatures, a y-intercept is small in each
straight line representing the characteristic and thus each
straight line is considered to represent a proportional
relationship between x and y.
[0105] Herein, when the logarithms of the concentrations y in FIG.
10 are plotted against an inverse number of an absolute temperature
(1/T)(10.sup.3.times.1/K), characteristics C12, C13, and C14 in
FIG. 11 are obtained. Herein, the characteristic C12 shows the
plotted results at 10 Torr and, likewise, the characteristics C13
and C14 show the plotted results at 20 Torr and 30 Torr,
respectively. From FIG. 11, it is seen that, in the x-y plane, the
slopes of the graphs each representing the relationship between x
and y are substantially constant regardless of the pressure.
Further, the characteristics C12, C13, and C14 can be approximated
by y=6E+13e.sup.-21.965x, y=3E+13e.sup.-21.983x, and
y=2E+13e.sup.-21.953x, respectively. Herein, x is a value of 1/T
expressed by the absolute temperature.
[0106] From the above formulas and the characteristics C12 to C14,
the slopes of the characteristics C12 to C14 represent activation
energies Ea in constant pressure states of 10 Torr, 20 Torr, and 30
Torr, respectively, and values thereof are 1.893 eV, 1.894 eV, and
1.892 eV, respectively.
[0107] On the other hand, the evaporation rate of the material H,
i.e. the concentration of the material H, can be represented by the
following formula (I).
V(%)=(Ko/P).times.e.sup.-Ea/kT (1)
where Ko is a constant (%Torr), P is a pressure (Torr), k is a
Boltzmann constant (=8.617.times.10.sup.-5 eV/K), and Ea is an
activation energy (eV). Since the material H concentrations given
by the formula (I) should be equal to the formulas derived from
FIG. 11, i.e. y=6E+13e.sup.-21.965x, y=3E+13e.sup.-21.983x and
y=2E+13e.sup.-21.953x, the constant Ko can be derived from the
formula (I) and the formulas obtained from FIG. 11 by giving the
temperatures and the material H concentrations. In other words, the
evaporation characteristic of the material H can be defined by
these parameters Ea and Ko.
[0108] Tables 1, 2, and 3 show material H concentrations in 10
cc/min at pressures of 10, 20, and 30 Torr, respectively, and
values of Ko.
TABLE-US-00001 TABLE 1 Material H Concentration in 10 cc/min at a
pressure of 10 Torr Temperature Material H Concentration K
(Constant) Value 430.degree. C. 1.68% 5.903 .times. 10.sup.14 (%
.cndot. Torr) 460.degree. C. 6.01% 5.908 .times. 10.sup.14 (%
.cndot. Torr) 000.degree. C. 0.00% 0.000 .times. 10.sup.14 (%
.cndot. Torr)
TABLE-US-00002 TABLE 2 Material H Concentration in 10 cc/min at a
pressure of 20 Torr Temperature Material H Concentration K
(Constant) Value 420.degree. C. 0.54% 5.968 .times. 10.sup.14 (%
.cndot. Torr) 440.degree. C. 1.37% 6.220 .times. 10.sup.14 (%
.cndot. Torr) 460.degree. C. 3.05% 5.992 .times. 10.sup.14 (%
.cndot. Torr)
TABLE-US-00003 TABLE 3 Material H Concentration in 10 cc/min at a
pressure of 30 Torr Temperature Material H Concentration K
(Constant) Value 430.degree. C. 0.54% 5.708 .times. 10.sup.14 (%
.cndot. Torr) 440.degree. C. 0.91% 6.211 .times. 10.sup.14 (%
.cndot. Torr) 450.degree. C. 1.28% 5.710 .times. 10.sup.14 (%
.cndot. Torr)
[0109] The constant Ko of the material H is derived in Tables 1 to
3. When a material is unknown, if a measured value of the
concentration at a particular temperature is obtained and further
an activation energy Ea is obtained from the temperature dependence
of the organic EL raw material concentration like that shown in
FIG. 11, a value of the constant Ko is determined and, by comparing
this value with Tables 1 to 3, the unknown material can be
identified as the material H.
[0110] Likewise, the same evaluation as that of the material H was
also carried out for an organic EL raw material known as a material
C. As a result of this, the results similar to those on the
material H were obtained.
[0111] That is, referring to FIG. 12, there are shown the results
of measuring time-dependent changes of the material C concentration
in a carrier gas in the state where evaporating dishes are heated
at 370.degree. C. As is also clear from FIG. 12, when the material
C is heated at 370.degree. C. and the pressure is changed, it is
possible to increase the material C concentration in the carrier
gas as the pressure decreases and, further, the material C
concentration is substantially constant. That is, in the state of
being maintained at 370.degree. C. and 75 Torr, a concentration of
about 8000 ppm can be maintained over a long period of time.
Subsequently, as the pressure is reduced to 30 Torr, 20 Torr, and
10 Torr, the material C concentration in the carrier gas increases
and, further, the time of high concentration is shortened. This
means that a material C film can be quickly deposited by reducing
the pressure.
[0112] Likewise, even by changing the pressure in the state of
being heated at 330.degree. C. and 350.degree. C., the results
similar to those in FIG. 12 were obtained. Further, when the
temperature was changed in the range of 430.degree. C. to
450.degree. C. in the state where the pressure was maintained
constant (e.g. at 30 Torr), the results similar to those in FIG. 8
for the material H were also obtained for the material C.
[0113] Taking this into account, the relationship between pressure
and concentration in the state where the temperature of the
material C was maintained constant was measured, then, as shown in
FIG. 13, there were obtained characteristics Cm1, Cm2, and Cm3
representing the relationships between concentration and pressure
at temperatures of 330.degree. C., 350.degree. C., and 370.degree.
C., respectively. The characteristics Cm1 to Cm3 can be
approximated by y=11.51x-0.0009, y=19.575x+0.1238, and
y=51.568x+0.0113, respectively. Also with respect to the material
C, y-intercepts of Cm1 to Cm3 are all small and thus it can be said
that x and y are in a proportional relationship.
[0114] Further, like in FIG. 11 relating to the material H, the
relationships between concentration and temperature
(1/T)(10.sup.3.times.1/K) at respective pressures of 10 Torr, 20
Torr, and 30 Torr, while each pressure was maintained constant,
were also derived for the material C. Then, characteristics Cm4,
Cm5, and Cm6 as shown in FIG. 14 were obtained for the respective
pressures of 10 Torr, 20 Torr, and 30 Torr. Like in the case of the
material H, it can be said that the slopes of Cm4 to Cm6 in the x-y
plane are substantially constant regardless of the pressure. When
activation energies Ea are derived from the characteristics Cm4,
Cm5, and Cm6 at the pressures of 10, 20, and 30 Torr, there are
obtained 1.253 (eV), 1.250 (eV), and 1.249 (eV), respectively.
[0115] On the other hand, using the formula (I), the constant Ko is
derived from the temperatures and the material C concentrations at
the pressure of 10 Torr, which is as shown in Table 4. Further, the
constant Ko is derived from the temperatures and the material C
concentrations at the pressures of 20 Torr and 30 Torr, which is as
shown in Tables 5 and 6.
TABLE-US-00004 TABLE 4 Material C Concentration in 10 cc/min at a
pressure of 10 Torr Temperature Material C Concentration K
(Constant) Value 330.degree. C. 1.15% 3.235 .times. 10.sup.11 (%
.cndot. Torr) 350.degree. C. 2.05% 2.670 .times. 10.sup.11 (%
.cndot. Torr) 370.degree. C. 5.15% 3.232 .times. 10.sup.11 (%
.cndot. Torr)
TABLE-US-00005 TABLE 5 Material C Concentration in 10 cc/min at a
pressure of 20 Torr Temperature Material C Concentration K
(Constant) Value 330.degree. C. 0.58% 3.111 .times. 10.sup.11 (%
.cndot. Torr) 350.degree. C. 1.12% 2.779 .times. 10.sup.11 (%
.cndot. Torr) 370.degree. C. 2.59% 3.120 .times. 10.sup.11 (%
.cndot. Torr)
TABLE-US-00006 TABLE 6 Material C Concentration in 10 cc/min at a
pressure of 30 Torr Temperature Material C Concentration K
(Constant) Value 330.degree. C. 0.38% 3.635 .times. 10.sup.11 (%
.cndot. Torr) 350.degree. C. 0.75% 3.301 .times. 10.sup.11 (%
.cndot. Torr) 370.degree. C. 1.70% 3.513 .times. 10.sup.11 (%
.cndot. Torr)
[0116] This means that when the temperature, the concentration, and
the pressure are known, the constant Ko of the formula (I)
determining the evaporation rate can be derived and it is possible
to identify a material based on the Ko value. In other words, this
means that when the temperature is set to 250 to 500.degree. C.
enabling efficient evaporation and gas supply control, preferably
300 to 450.degree. C., the concentration is set to 0.1 to 10%
enabling efficient film formation, and the pressure is set to
10.sup.-3 Torr or more, a material having an Ea value and a
constant Ko satisfying the formula (I) determining the evaporation
rate can be practically used for film formation by carrier gas
transport.
[0117] As is also clear from a comparison between Tables 1 to 3 and
Tables 4 to 6, the material H and the material C largely differ
from each other in value of Ko. That is, while the Ko values of the
material H are on the order of 1014, the Ko values of the material
C are on the order of 10.sup.11. Since a Ko value is conjectured to
have a value unique to a material, it is possible to identify
various materials based on Ko values thereof.
[0118] That is, the Ko values of the material H in the range of 10
Torr to 30 Torr are distributed in the range of
5.710.times.10.sup.14 (%Torr) to 6.211.times.10.sup.14 (%Torr) as
shown in Tables 1 to 3. On the other hand, the Ko values of the
material C in the range of 10 Torr to 30 Torr are distributed in
the range of 2.670.times.10.sup.11 (%Torr) to 3.635.times.10.sup.11
(%Torr) as shown in Tables 4 to 6.
[0119] Likewise, various materials other than the material H and
the material C can be identified by Ko values. In this manner, one
feature of this invention is to identify a material by a Ko
value.
[0120] Further, if parameters Ea and Ko of an organic EL raw
material are obtained, it is possible to determine the
manufacturing conditions using the formula (I). Specifically, in
general, when manufacturing organic EL devices, there are various
restrictions to the film-forming conditions for film formation of
an organic EL raw material. For example, if the manufacturing
volume per unit time is determined, the film-forming time of one
film is determined and, as a result, the concentration of the
organic EL raw material in a carrier gas is determined. Further,
when the organic EL raw material is determined, since it is
necessary to evaporate it without decomposition, the heating
temperature is also restricted. Since there is a limit to an
achievable degree of vacuum due to the performance of a
manufacturing apparatus, it is considered that the pressure in
evaporation means may also be restricted.
[0121] In the case where the film-forming condition is restricted
as described above, it is possible to determine the restricted
film-forming condition within the restriction and then to determine
other conditions from the determined film-forming condition and the
formula (I).
[0122] To give one example, in the case where the lower limit of
concentration is determined from the production volume and the
upper limit of evaporation temperature is determined from the
characteristics of an organic EL raw material, a necessary pressure
value can be obtained by determining the concentration and the
temperature within the restrictions, respectively, substituting
them into the formula (I), and solving it.
INDUSTRIAL APPLICABILITY
[0123] According to this invention, it is possible to provide a
film-forming material suitable for film formation using a carrier
gas. Further, according to this invention, it is possible to derive
from experimental data a parameter that defines a characteristic of
an organic EL raw material and to predict an organic EL raw
material based on this parameter and, therefore, it is quite
effective for experiments and studies of organic EL raw materials.
Further, using this parameter, it is possible to determine the
conditions for manufacturing organic EL devices. This invention is
not merely limited to the organic EL raw materials, but can be
applied to various film-forming materials.
* * * * *