U.S. patent application number 13/315312 was filed with the patent office on 2012-04-05 for light emitting device and manufacturing method thereof.
This patent application is currently assigned to SEMICONDUCTOR ENERGY LABORATORY CO., LTD.. Invention is credited to Toru Takayama, Shunpei YAMAZAKI.
Application Number | 20120080669 13/315312 |
Document ID | / |
Family ID | 32032210 |
Filed Date | 2012-04-05 |
United States Patent
Application |
20120080669 |
Kind Code |
A1 |
YAMAZAKI; Shunpei ; et
al. |
April 5, 2012 |
LIGHT EMITTING DEVICE AND MANUFACTURING METHOD THEREOF
Abstract
A light emitting element having an organic compound, which can
be extended its longevity is provided. According to the present
invention, there is provided a constitution in which, in order to
protect a light emitting element from moisture, an inorganic
insulating film 312a, a stress relaxation layer 312b having
transparency and a hygroscopic property, and an inorganic
insulating film 312c are repeatedly laminated over a cathode. The
stress relaxation layer 312b having transparency and the
hygroscopic property uses at least one film selected from the group
consisting of a film comprising a same material as that of a layer
310, containing an organic compound, sandwiched between a cathode
and an anode, a layer capable of being formed by vapor deposition,
and a layer capable of being formed by coating.
Inventors: |
YAMAZAKI; Shunpei; (Tokyo,
JP) ; Takayama; Toru; (Atsugi, JP) |
Assignee: |
SEMICONDUCTOR ENERGY LABORATORY
CO., LTD.
Atsugi-shi
JP
|
Family ID: |
32032210 |
Appl. No.: |
13/315312 |
Filed: |
December 9, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11802961 |
May 29, 2007 |
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13315312 |
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10636545 |
Aug 8, 2003 |
7230271 |
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11802961 |
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Current U.S.
Class: |
257/40 ;
257/E51.026 |
Current CPC
Class: |
H01L 27/3244 20130101;
H01L 51/5259 20130101; H01L 2251/5315 20130101; H01L 51/5256
20130101; H01L 27/3211 20130101; H01L 51/5253 20130101 |
Class at
Publication: |
257/40 ;
257/E51.026 |
International
Class: |
H01L 51/54 20060101
H01L051/54 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2002 |
JP |
2002-169819 |
Aug 9, 2002 |
JP |
2002-233691 |
Claims
1. A bottom emission light emitting device comprising: a first
substrate; a light emitting element over the first substrate, the
light emitting element comprising: an anode over the first
substrate; an electroluminescent layer over the anode, the
electroluminescent layer including a first organic compound; and a
cathode over the electroluminescent layer; a layer over the light
emitting element, the layer including tris-8-quinolinolate aluminum
complex; and a second substrate over the layer, wherein the first
substrate and the anode are capable of transmitting light emitted
by the electroluminescent layer.
2. The bottom emission light emitting device according to claim 1,
further comprising a first inorganic insulating layer over the
cathode.
3. The bottom emission light emitting device according to claim 1,
further comprising a second inorganic insulating layer over the
layer.
4. The bottom emission light emitting device according to claim 1,
wherein a top surface of the cathode is in contact with the
layer.
5. The bottom emission light emitting device according to claim 1,
further comprising a TFT over the first substrate, wherein the TFT
is electrically connected to the light emitting element.
6. The bottom emission light emitting device according to claim 1,
wherein the layer is formed by vapor deposition.
7. The bottom emission light emitting device according to claim 1,
wherein the layer is a polymeric material layer containing
tris-8-quinolinolate aluminum complex, obtained by coating.
8. A semiconductor device comprising the bottom emission light
emitting device of claim 1, wherein the semiconductor device is at
least one member selected from a group consisting of a video
camera, a digital camera, a display, a car navigation system, a
personal computer, and a portable information terminal.
9. A bottom emission light emitting device comprising: a first
substrate; a light emitting element over the first substrate, the
light emitting element comprises: an anode over the first
substrate; an electroluminescent layer over the anode, the
electroluminescent layer includes an organic compound; and a
cathode over the electroluminescent layer; a layer over the light
emitting element, the layer includes the organic compound; and a
second substrate over the layer, wherein the first substrate and
the anode are capable of transmitting light emitted by the
electroluminescent layer.
10. The bottom emission light emitting device according to claim 9,
further comprising a first inorganic insulating layer over the
cathode.
11. The bottom emission light emitting device according to claim 9,
further comprising a second inorganic insulating layer over the
layer.
12. The bottom emission light emitting device according to claim 9,
wherein a top surface of the cathode is in contact with the
layer.
13. The bottom emission light emitting device according to claim 9,
wherein the light emitting element and a TFT electrically connected
to the light emitting element are provided over the first
substrate.
14. The bottom emission light emitting device according to claim 9,
wherein the layer is formed by vapor deposition.
15. The bottom emission light emitting device according to claim 9,
wherein the layer is a polymeric material layer containing the
organic compound, obtained by coating.
16. The bottom emission light emitting device according to claim 9,
wherein the organic compound is at least one material selected from
a group consisting of 4,4'-bisbiphenyl, bathocuproin, and
4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine.
17. A semiconductor device comprising the bottom emission light
emitting device of claim 9, wherein the semiconductor device is at
least one member selected from a group consisting of a video
camera, a digital camera, a display, a car navigation system, a
personal computer, and a portable information terminal.
18. A bottom emission light emitting device comprising: a first
substrate; a light emitting element over the first substrate, the
light emitting element comprises: an anode over the first
substrate; an electroluminescent layer over the anode, the
electroluminescent layer includes tris-8-quinolinolate aluminum
complex; and a cathode over the electroluminescent layer; a layer
over the light emitting element, the layer includes
tris-8-quinolinolate aluminum complex; and a second substrate over
the layer, wherein the first substrate and the anode are capable of
transmitting light emitted by the electroluminescent layer.
19. The bottom emission light emitting device according to claim
18, further comprising a first inorganic insulating layer over the
cathode.
20. The bottom emission light emitting device according to claim
18, further comprising a second inorganic insulating layer over the
layer.
21. The bottom emission light emitting device according to claim
18, wherein a top surface of the cathode is in contact with the
layer.
22. The bottom emission light emitting device according to claim
18, wherein the light emitting element and a TFT electrically
connected to the light emitting element are provided over the first
substrate.
23. The bottom emission light emitting device according to claim
18, wherein the layer is formed by vapor deposition.
24. The bottom emission light emitting device according to claim
18, wherein the layer is a polymeric material layer containing
tris-8-quinolinolate aluminum complex, obtained by coating.
25. A semiconductor device comprising the bottom emission light
emitting device of claim 18, wherein the semiconductor device is at
least one member selected from a group consisting of a video
camera, a digital camera, a display, a car navigation system, a
personal computer, and a portable information terminal.
26. A bottom emission light emitting device comprising: a first
substrate; a light emitting element over the first substrate, the
light emitting element comprising: an anode over the first
substrate; an electroluminescent layer over the anode, the
electroluminescent layer including a first organic compound; and a
cathode over the electroluminescent layer; a layer over the light
emitting element, the layer including at least one material
selected from a group consisting of 4,4'-bisbiphenyl, bathocuproin,
and 4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine,
and a second substrate over the layer, wherein the first substrate
and the anode are capable of transmitting light emitted by the
electroluminescent layer.
27. The bottom emission light emitting device according to claim
26, further comprising a first inorganic insulating layer over the
cathode.
28. The bottom emission light emitting device according to claim
26, further comprising a second inorganic insulating layer over the
layer.
29. The bottom emission light emitting device according to claim
26, wherein a top surface of the cathode is in contact with the
layer.
30. The bottom emission light emitting device according to claim
26, further comprising a TFT over the first substrate, wherein the
TFT is electrically connected to the light emitting element.
31. The bottom emission light emitting device according to claim
26, wherein the layer is formed by vapor deposition.
32. The bottom emission light emitting device according to claim
26, wherein the layer is a polymeric material layer containing the
one material selected from a group consisting of 4,4'-bisbiphenyl,
bathocuproin, and
4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine,
obtained by coating.
33. A semiconductor device comprising the bottom emission light
emitting device of claim 26, wherein the semiconductor device is at
least one member selected from a group consisting of a video
camera, a digital camera, a display, a car navigation system, a
personal computer, and a portable information terminal.
34. A bottom emission light emitting device comprising: a first
substrate; a light emitting element over the first substrate, the
light emitting element comprising: an anode over the first
substrate; an electroluminescent layer over the anode, the
electroluminescent layer including a first organic compound; and a
cathode over the electroluminescent layer; and a layer over the
light emitting element, the layer including tris-8-quinolinolate
aluminum complex; a space over the layer; and a second substrate
over the space, wherein the first substrate and the anode are
capable of transmitting light emitted by the electroluminescent
layer.
35. The bottom emission light emitting device according to claim
34, further comprising a first inorganic insulating layer over the
cathode.
36. The bottom emission light emitting device according to claim
34, further comprising a second inorganic insulating layer over the
layer.
37. The bottom emission light emitting device according to claim
34, wherein a top surface of the cathode is in contact with the
layer.
38. The bottom emission light emitting device according to claim
34, further comprising a TFT over the first substrate, wherein the
TFT is electrically connected to the light emitting element.
39. The bottom emission light emitting device according to claim
34, wherein the layer is formed by vapor deposition.
40. The bottom emission light emitting device according to claim
34, wherein the layer is a polymeric material layer containing
tris-8-quinolinolate aluminum complex, obtained by coating.
41. A semiconductor device comprising the bottom emission light
emitting device of claim 34, wherein the semiconductor device is at
least one member selected from a group consisting of a video
camera, a digital camera, a display, a car navigation system, a
personal computer, and a portable information terminal.
42. The bottom emission light emitting device according to claim
34, wherein the space is filled with an inert gas.
43. A bottom emission light emitting device comprising: a first
substrate; a light emitting element over the first substrate, the
light emitting element comprises: an anode over the first
substrate; an electroluminescent layer over the anode, the
electroluminescent layer includes an organic compound; and a
cathode over the electroluminescent layer; a layer over the light
emitting element, the layer includes the organic compound; a space
over the layer; and a second substrate over the space, wherein the
first substrate and the anode are capable of transmitting light
emitted by the electroluminescent layer.
44. The bottom emission light emitting device according to claim
43, further comprising a first inorganic insulating layer over the
cathode.
45. The bottom emission light emitting device according to claim
43, further comprising a second inorganic insulating layer over the
layer.
46. The bottom emission light emitting device according to claim
43, wherein a top surface of the cathode is in contact with the
layer.
47. The bottom emission light emitting device according to claim
43, wherein the light emitting element and a TFT electrically
connected to the light emitting element are provided over the first
substrate.
48. The bottom emission light emitting device according to claim
43, wherein the layer is formed by vapor deposition.
49. The bottom emission light emitting device according to claim
43, wherein the layer is a polymeric material layer containing the
organic compound, obtained by coating.
50. The bottom emission light emitting device according to claim
43, wherein the organic compound is at least one material selected
from a group consisting of 4,4'-bisbiphenyl, bathocuproin, and
4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine.
51. A semiconductor device comprising the bottom emission light
emitting device of claim 43, wherein the semiconductor device is at
least one member selected from a group consisting of a video
camera, a digital camera, a display, a car navigation system, a
personal computer, and a portable information terminal.
52. The bottom emission light emitting device according to claim
43, wherein the space is filled with an inert gas.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor device
having a circuit comprised of thin film transistor (hereinafter,
TFT) and a manufacturing method thereof. For instance, the present
invention relates to a light emitting device using a light emitting
element which has a film containing an organic compound
(hereinafter, organic compound layer) between a pair of electrodes
and which can give fluorescence or luminescence by receiving an
electric field, and a manufacturing method thereof. The light
emitting device referred to in the present specification is an
image display device, a light emitting device or a light source
(including lighting installation). Additionally, the following are
included in examples of the light emitting device: a module wherein
a connector, for example, a flexible printed circuit (FPC) or a
tape automated bonding (TAB) tape, or a tape carrier package (TCP)
is set up onto a light emitting element; a module wherein a printed
wiring board is set to the tip of a TAB tape or a TCP; and a module
wherein integrated circuits (IC) are directly mounted on a light
emitting element in a chip on glass (COG) manner.
[0003] In addition, the semiconductor device in this specification
is the device in general which can function by utilizing the
semiconductor characteristics. An electro-optic device, a light
emitting device, a semiconductor circuit and an electronic device
are all semiconductor devices.
[0004] 2. Related Art
[0005] A light emitting element using an organic compound as a
luminous body, characterized by its thin thickness, light weight,
high-speed response, low-voltage DC drive, and so on, has been
expected its application to a next-generation flat panel display.
Especially a display device, in which light emitting elements are
arranged in a matrix configuration, is considered that it has an
advantage over the conventional liquid crystal display device in
terms of its wide angle and superior visibility.
[0006] A light emitting mechanism of a light emitting element may
be as follows. That is, when a voltage is applied on the organic
compound layer sandwiched between a pair of the electrodes, an
electron injected from the cathode and an electron hole injected
from the anode are brought into recombination with each other at
the luminescence center of the organic compound layer to form a
molecular excitation. Subsequently, light emission is occurred by
discharging energy when the molecular excitation returns to a
ground state. There are two types of the excitation state, a
singlet exciton and a triplet exciton. The light emission may
achieved in either state.
[0007] The light emitting device constructed of a plurality of
light emitting elements arranged in a matrix configuration may be
operated by a passive matrix drive (passive matrix type) and an
active matrix drive (active matrix type). However, when the pixel
density increases, it may be preferable to use the active matrix
type in which a switch is provided for every pixel (or every dot)
since it can be driven at a low voltage.
[0008] Furthermore, low-molecular type material and high-molecular
type (polymer) material have been studied for an organic compound
to be provided as an organic compound layer (i.e., a light emitting
layer in the strict sense), which may be a center of a light
emitting element. Among them, the attention has been focused on the
high-molecular type material because of its high heat resistance
and convenience in handling compared with the low-molecular type
material.
[0009] For forming a film from an organic compound, vapor
deposition, spin-coating, and ink jetting have been known. Among
them, for realizing a full-color image formation using a polymer
material, the spin-coating and the ink-jetting have been
particularly known.
[0010] The disadvantage of a light emitting element having an
organic compound is easily deteriorated by various factors, so that
the greatest object thereof is to increase its reliability (make
longer its life span).
[0011] A light emitting element having an organic compound is
deteriorated mainly by oxygen and moisture. As a defective state
due to this, the partial deterioration of luminance and nonluminous
region are occurred.
[0012] The expansion of nonluminous region may proceed merely with
time or with time during which light emitting element is driven.
Particularly, in the case nonluminous region is occurred soon after
manufacturing a light emitting material having an organic compound,
the expansion of nonluminous region is often proceeded with time,
and is sometimes end up with whole nonluminous region.
[0013] In addition, the nonluminous region tends to generate from a
marginal portion of luminous region, and expands with time as if
contracting the luminous region. Therefore, this defective mode is
called shrink.
[0014] These defects cause a certain light emitting element to be a
nonluminous element at high speed, particularly, with respect to an
active matrix type light emitting device, because shrink heavily
damages such a small light emitting region in the active light
emitting device. Further, in the case the area of luminous region
is small, the proportion of nonluminous region becomes bigger,
according to the reduction of luminous region. Therefore, when
manufacturing a display device using a light emitting element, it
is difficult to obtain a display device which has a high-definition
(basically a pitch of a pixel area is small) and higher
reliability.
[0015] Non luminous region such as a black spot may be generated
just after manufacturing a light emitting element having an organic
compound, This defective mode is referred to as dark spot. And this
dark spot may be enlarged with time.
SUMMARY OF THE INVENTION
[0016] An object of the present invention is to extend longevity of
a light emitting element having an organic compound.
[0017] According to the present invention, in order to protect a
light emitting element from moisture, there is provided a
structure, in which a stress relaxation layer having transparency
and a hygroscopic property and an inorganic insulating film are
repeatedly laminated over a cathode. The stress relaxation layer
having transparency and the hygroscopic property uses at least one
film selected from the group consisting of: a film comprising a
same material as that of a layer, which is containing an organic
compound and sandwiched between a cathode and an anode; a layer
capable of being formed by vapor deposition; and a layer capable of
being formed by coating.
[0018] As for such inorganic insulating films, a silicon nitride
film to be obtained by sputtering or CVD, a silicon oxide film, a
silicon oxynitride film (SiNO film (component ratio: N>O), or
SiON film (component ratio: N<O)), or a thin film containing
carbon as a primary component (for example, a DLC film, or a CN
film) can be used. These inorganic insulating films each have a
high blocking effect against moisture; however, as film thickness
thereof is increased, a film stress is increased and they tend to
be partially peeled or totally removed as a film. Nevertheless,
stress can be relaxed and, also, moisture can be absorbed by
sandwiching the stress relaxation layer between the inorganic
insulating films. Even when a minute hole is formed in the
inorganic insulating film, the minute hole can be blocked by the
stress relaxation layer and, further, by providing another
inorganic insulating film thereover, an extremely high blocking
effect against moisture or oxygen can be attained. A laminate
formed in such a manner as described above is optimum as a sealing
film of the light emitting element in which the layer containing
the organic compound is allowed to be a light emitting layer.
[0019] Herein, a light emitting element to be formed by a cathode,
an EL layer and an anode is defined as an EL element. There are two
types of methods in such EL elements, namely, a type (referred to
as passive matrix type) in which an EL layer is formed between two
types of stripe-shaped electrodes which are orthogonally arranged
against each other, and the other type (referred to as active
matrix type) in which an EL layer is formed between a pixel
electrode which is connected to a TFT and aligned in a matrix
manner, and a counter electrode. The sealing film according to the
invention can be applied to any one of the above-described two
types.
[0020] According to the invention, the above-described laminate may
be provided one or both surfaces of the substrate for a sealing. By
using the resultant substrate as a sealed substrate of the light
emitting element, the sealed substrate having an extremely high
blocking effect against moisture or oxygen can be provided.
Particularly, the laminate is effective when a plastic substrate,
which has a lower blocking effect than that of a glass substrate,
is used as a sealed substrate.
[0021] A constitution according to the invention disclosed herein
is a light emitting device comprising a light emitting element
comprising a cathode, a layer containing an organic compound,
adjacent to the cathode, and an anode adjacent to the layer
containing the organic compound over a substrate having an
insulating surface, wherein the light emitting element is covered
by a laminate comprising a first inorganic insulating film, a film
having a hygroscopic property and transparency, and a second
inorganic insulating film.
[0022] Further, the constitution according to the invention
disclosed herein is also applicable to a top emission type light
emitting device. Another constitution according to the invention is
a light emitting device in which a light emitting element
comprising a cathode, a layer containing an organic compound,
adjacent to the cathode, and an anode adjacent to the layer
containing the organic compound is sandwiched between a first
substrate and a second substrate, wherein the light emitting
element provided over the first substrate is covered by a laminate
comprising a first inorganic insulating film, a film having a
hygroscopic property, and a second inorganic insulating film; and
luminescence from the light emitting element is allowed to pass
through the second substrate, thereby being recognized by a
user.
[0023] Further, the constitution according to the invention
disclosed herein is also applicable to a bottom emission type light
emitting device. Still another constitution according to the
invention is a light emitting device in which a light emitting
element comprising a cathode, a layer containing an organic
compound, adjacent to the cathode, and an anode adjacent to the
layer containing the organic compound is sandwiched between a first
substrate and a second substrate, wherein the light emitting
element provided over the first substrate is covered by a laminate
comprising a first inorganic insulating film, a film having a
hygroscopic property and transparency, and a second inorganic
insulating film; and luminescence from the light emitting element
is allowed to pass through the first substrate, thereby being
recognized by a user. Since the above constitution is a bottom
emission type, the film having the hygroscopic property may be
transparent, translucent, or may have a light blocking
property.
[0024] Further, in any one of the above-described constitutions,
the film having the hygroscopic property and transparency has a
smaller stress than that of at least one of the first inorganic
insulating film and the second inorganic insulating film, and has
an effect to relax the stress of the first inorganic insulating
film and the second inorganic insulating film.
[0025] Further, in any one of the above-described constitutions, at
least one of the first inorganic insulating film and the second
inorganic insulating film comprises at least one film selected from
the group consisting of: a silicon nitride film to be obtained by
sputtering or CVD, a silicon oxide film, a silicon oxynitride film,
a DLC film, a CN film, and a laminate thereof. Among other things,
it is desirable that at least one of the first inorganic insulating
film and the second inorganic insulating film is a silicon nitride
film formed by RF sputtering using silicon as a target.
[0026] Further, the dense silicon nitride film to be obtained by RF
sputtering using silicon as a target effectively prevents a
fluctuation of a threshold voltage to be caused by contaminating
the TFT with an alkali metal or an alkali earth metal such as
sodium, lithium, and magnesium, and also, exerts an extremely high
blocking effect against moisture or oxygen. Still further, in order
to enhance the blocking effect, it is desirable that contents of
oxygen and hydrogen in the silicon nitride film is 10 atomic % or
less and, preferably, 1 atomic % or less.
[0027] Specific sputtering conditions are set such that a nitrogen
gas or a mixed gas of the nitrogen gas and a noble gas is used;
pressure is set to be in the range of from 0.1 Pa to 1.5 Pa;
frequency is set to be in the range of from 13 MHz to 40 MHz; power
is set to be in the range of from 5 W/cm.sup.2 to 20 W/cm.sup.2; a
substrate temperature is set to be in the range of from room
temperature to 350.degree. C.; a distance between a silicon target
(1 to 10 .OMEGA.cm) and the substrate is set to be in the range of
from 40 mm to 200 mm; and back pressure is set to be
1.times.10.sup.-3 Pa or less. A heated noble gas may be flown to a
back surface of the substrate. For example, a dense silicon nitride
film obtained under the conditions of flow ratio of Ar:N.sub.2=20
sccm:20 sccm; pressure: 0.8 Pa; frequency: 13.56 MHz; power: 16.5
W/cm.sup.2; substrate temperature: 200.degree. C.; distance between
silicon target and substrate: 60 mm; and back pressure:
3.times.10.sup.-5 Pa has characteristics that etching speed
(referred to speed at the time etching is performed at 20.degree.
C. by using LAL500; same is applied to descriptions below) is as
slow as 9 nm/min or less (preferably, in the range of from 0.5
nm/min to 3.5 nm/min) and a hydrogen concentration is as low as
1.times.10.sup.21 atoms/cm.sup.3 or less (preferably,
5.times.10.sup.20 atoms/cm.sup.3 or less). The term "LAL500" used
herein denotes "LAL500 SA buffered hydrofluoric acid" available
from Hashimoto Kasei Co., Ltd., meaning an aqueous solution of
NH.sub.4HF.sub.2 (7.13%) and NH.sub.4F (15.4%).
[0028] Further, the silicon nitride film obtained by sputtering has
properties of specific inductive capacity: 7.02 to 9.3; refraction
factor: 1.91 to 2.13; internal stress: 4.17.times.10.sup.8
dyn/cm.sup.2; and etching speed: 0.77 nm/min to 1.31 nm/min. The
internal stress changes negative and positive signs thereof
depending on compression stress and tensile stress, but it is
treated herein as an absolute figure. A Si concentration and an N
concentration measured by RBS of the silicon nitride film formed by
sputtering are 37.3 atomic % and 55.9 atomic %, respectively. A
hydrogen concentration, an oxygen concentration, and a carbon
concentration measured by SIMS of the silicon nitride film formed
by sputtering are 4.times.10.sup.20 atoms/cm.sup.3,
8.times.10.sup.20 atoms/cm.sup.3, and 1.times.10.sup.19
atoms/cm.sup.3, respectively. A light transmission factor of the
silicon nitride film formed by sputtering in the visible light
region is 80% or more.
[0029] In any one of the above-described constitutions, the thin
film containing carbon as a primary component denotes at least one
film selected from the group consisting of: a diamond-like carbon
film (referred to also as DLC film) having a film thickness in the
range of from 3 nm to 50 nm, a carbon nitride film (referred to as
CN film), and an amorphous carbon film. The DLC film has an
SP.sup.3 bond as a carbon-carbon bond on the basis of
short-distance order, but is in an amorphous state on the basis of
a macroscopic viewpoint. A composition of the DLC film is carbon:
70 atomic % to 95 atomic %; and hydrogen: 5 atomic % to 30 atomic
%. The DLC film is extremely hard and has an excellent insulation
property. Further, the DLC film is chemically stable, is not easily
change its property and is thin in thickness. Thermal conductivity
of the DLC film is in the range of from 200 W/mK to 600 W/mK,
thereby being capable of releasing heat generated at the time of
start-up. As described above, the DLC film has characteristics of
low gas permeability against steam or oxygen. It is known that DLC
film has hardness in the range of from 15 GPa to 25 GPa which is
measured by a micro-hardness scale.
[0030] The DLC film can be formed by at least one method selected
from the group consisting of: plasma CVD (as a typical example, RF
plasma CVD, microwave CVD, electron cyclotron resonance (ECR) CVD,
hot-filament CVD), combustion-flame, sputtering, ion beam vapor
deposition, and laser vapor deposition. By using any one of these
film-forming methods, the DLC film which has an excellent adhesion
can be obtained. The DLC film is formed by setting a substrate over
a cathode. In another case, a dense and hard film can be obtained
by applying a negative bias to utilize an ion collision to some
extent.
[0031] As for reaction gases to be used in forming of the DLC film,
a hydrogen gas and a hydrocarbon type gas (for example, CH.sub.4,
C.sub.2H.sub.2, or C.sub.6H.sub.6) are used. These gases are
ionized by glow discharge and the resultant ions, after being
accelerated in velocity, collides with a cathode which is applied
with negative self-bias, thereby forming a film. In such manner, a
dense and smooth DLC film can be obtained. Further, the resultant
DLC film is a transparent or translucent insulating film against
visible light. The term "transparent against visible light" used
herein is intended to mean that a transmission factor of the
visible light is in the range of from 80% to 100%, while the term
"translucent against visible light" used herein is intended to mean
that a transmission factor of the visible light is in the range of
from 50% to 80%.
[0032] As for reaction gases to be used in forming of the CN film,
a nitrogen gas, and a hydrocarbon type gas (for example,
C.sub.2H.sub.2, or C.sub.2H.sub.4) may be used.
[0033] In any one of the above-described constitutions, the film
having the hygroscopic property and transparency is characterized
by being a material film to be obtained by vapor deposition. For
example, an alloy film of MgO, SrO.sub.2, SrO, CaF.sub.2, CaN or
the like, or a material film containing an organic compound such as
.alpha.-NPD (4,4'-bis-[N-(naphthyl)-N-phenyl-amino]biphenyl), BCP
(bathocuproin), MTDATA
(4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino) triphenylamine, or
Alq.sub.a (a tris-8-quinolinolate aluminum complex) may be used.
Therefore, the film having a hygroscopic property and transparency
sometimes comprises a same material as that of at least one layer
of a plurality of layers which constitute the layer containing the
organic compound sandwiched between the cathode and the anode.
[0034] Further, the film having the hygroscopic property and
transparency may be a polymeric material film containing an organic
compound, obtained by coating (inkjetting or spin coating). For
example, polyaniline or a polythiophene derivative (PEDOT) may be
used.
[0035] Further, the invention is not limited to the laminate of
cathode/first inorganic insulating film/film having hygroscopic
property and transparency/second inorganic insulating film, but a
laminate having more layers than the above laminate such as
cathode/film having hygroscopic property and transparency/first
inorganic insulating film/film having hygroscopic property and
transparency/second inorganic insulating film and cathode/first
inorganic insulating film/film having hygroscopic property and
transparency/second inorganic insulating film/film having
hygroscopic property and transparency/third inorganic insulating
film.
[0036] Further, in any one of the above-described constitutions, in
a case of manufacturing an active matrix type light emitting
device, a light emitting element and a TFT connected to the light
emitting element are provided over the first substrate.
[0037] A constitution according to the invention in regard to a
manufacturing method for obtaining the above-described structure is
a method for manufacturing a light emitting device comprising a
light emitting element comprising a cathode, a layer containing an
organic compound, adjacent to the cathode, and an anode adjacent to
the layer containing the organic compound over a substrate having
an insulating surface, the method, comprising the steps of: forming
a TFT, and an anode connected to the TFT over the substrate;
forming a layer containing an organic compound over the anode;
forming a cathode over the layer containing the organic compound;
forming a first inorganic insulating film over the cathode; forming
a layer having a hygroscopic property and transparency over the
first inorganic insulating film; and forming a second inorganic
insulating film over the film having the hygroscopic property and
transparency.
[0038] In the above-described constitution in regard to the
manufacturing method, the steps of: forming the layer containing
the organic compound; and forming the film having the hygroscopic
property and transparency is characterized by using vapor
deposition with resistance heating.
[0039] In the above-described constitution in regard to the
manufacturing method, the film having the hygroscopic property and
transparency has a smaller stress than that of at least one of the
first inorganic insulating film and the second inorganic insulating
film, and further, comprises a same material as that of at least
one layer of a plurality of layers constituting the layer
containing the organic compound sandwiched between the cathode and
the anode.
[0040] In the above-described constitution in regard to the
manufacturing method, at least one film of the first inorganic
insulating film and the second inorganic insulating film is a
silicon nitride film to be formed by RF sputtering using silicon as
a target.
[0041] Further, a substrate laminated with the first inorganic
insulating film, the film having a hygroscopic property and
transparency, and the second inorganic insulating film may be used
as a sealed substrate. Also, the constitution according to the
invention is a light emitting device in which a light emitting
element comprising a cathode, a layer containing an organic
compound, adjacent to the cathode, and an anode adjacent to the
layer containing the organic compound is sandwiched between a first
substrate and a second substrate, wherein a laminate comprising a
first inorganic insulating film, a film having a hygroscopic
property and transparency, and a second inorganic insulating film
is provided adjacent to the first substrate or the second
substrate.
[0042] Further, a substrate in which the silicon nitride film
formed over one or both surfaces thereof by RF sputtering using
silicon as a target may be also a sealed substrate. Another the
constitution according to the invention is a light emitting device
in which a light emitting element comprising a cathode, a layer
containing an organic compound, adjacent to the cathode, and an
anode adjacent to the layer containing the organic compound is
sandwiched between a first substrate and a second substrate,
wherein a silicon nitride film formed by RF sputtering using
silicon as a target is provided adjacent to the first substrate or
the second substrate.
[0043] In the above-described constitution, the silicon nitride
film has an etching speed of 9 nm/min or less, a hydrogen
concentration of 1.times.10.sup.21 atoms/cm.sup.3 or less and, an
oxygen concentration in the range of from 5.times.10.sup.18
atoms/cm.sup.3 to 5.times.10.sup.21 atmos/cm.sup.3. Further, in the
above-described constitution, at least one of the first substrate
and the second substrate is a plastic substrate. Particularly, the
constitution is effective, when a plastic substrate which has a
lower blocking effect than that of a glass substrate is used as a
sealed substrate.
[0044] The plastic substrate is not particularly limited as long as
it has flexibility, and the plastic substrate comprises at least
one member selected from the group consisting of: polyethylene
terephthalate (PET), polyether sulfone (PES), polyethylene
naphthalate (PEN), polycarbonate (PC), nylon, polyether ether
ketone (PEEK), polysulfone (PSF), polyether imide (PEI),
polyallylate (PAR), polybutylene terephthalate (PBT), and
polyimide.
[0045] An EL element is constituted such that an EL layer is
sandwiched between a pair of electrodes, however, the EL layer
ordinarily has a laminar constitution. As an illustrative example,
a laminar constitution of "hole transport layer/light emitting
layer/electron transport layer" proposed by Tang et al., Eastman
Kodak Company, is mentioned. This constitution has an extremely
high light emission efficiency and, almost all light emitting
devices under development now adopt this constitution.
[0046] As examples of other constitutions than those described
above, a constitution in which hole injection layer/hole transport
layer/light emitting layer/electron transport layer are laminated
in order over an anode, or another constitution in which hole
injection layer/hole transport layer/light emitting layer/electron
transport layer/electron injection layer are laminated in order
over the anode is permissible. A fluorescent dye or the like may be
doped in the light emitting layer. Further, these layers may be
formed by using any one material selected from the group consisting
of: a low molecular type material, a polymeric material, and an
inorganic material.
[0047] Herein, all the layers which are sandwiched between the
cathode and the anode are generically denoted as a layer containing
an organic compound (referred to also as EL layer). Therefore, the
above-described hole injection layer, hole transport layer, light
emitting layer, electron transport layer and electron injection
layer are all included in the EL layer. These layers can be formed
by using at least one material selected from the group consisting
of: a low molecular type organic compound material, a middle
molecular type organic compound material, a polymeric organic
compound material, and mixtures thereof. Further, a mixed layer in
which an electron transport type material and a hole transport type
material are appropriately mixed, or a mixed bonding in which a
mixed region is formed in a bond interface of each material may be
formed.
[0048] Further, carbazole type CBP+Ir (ppy).sub.3 is an organic
compound (referred to also as triplet compound) which can obtain
luminescence (phosphorescence) from a triplet excited state
thereof. This compound can also be used as a light emitting layer
according to the invention. Since the luminescence
(phosphorescence) from the triplet excited state has higher light
emission efficiency than another luminescence (fluorescence) from a
singlet excited state, the luminescence (phosphorescence) can
reduce drive voltage (voltage required for allowing an organic
light emitting element to emit light).
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIGS. 1A and 1B are cross-sectional views of Embodiment Mode
1, respectively;
[0050] FIGS. 2A and 2B are cross-sectional views of Embodiment Mode
2, respectively;
[0051] FIGS. 3A and 3B are cross-sectional views of Embodiment Mode
3, respectively;
[0052] FIGS. 4A and 4B are a top view and a cross-sectional view of
Embodiment 1, respectively;
[0053] FIGS. 5A and 5B are a top view and a cross-sectional view of
Embodiment 1, respectively;
[0054] FIG. 6 shows a schematic diagram of a manufacturing
apparatus according to Embodiment 2;
[0055] FIGS. 7A to 7D show schematic views of a vapor deposition
mask according to Embodiment 3, respectively;
[0056] FIGS. 8A and 8B each show a schematic diagram explaining an
element constitution according to Embodiment 4;
[0057] FIGS. 9A to 9E schematically illustrate examples of
electronic apparatuses according to Embodiment 5;
[0058] FIGS. 10A to 10 C schematically illustrate examples of
electronic apparatuses according to Embodiment 5;
[0059] FIGS. 11A and 11B each show a schematic diagram of a module
according to Embodiment 6;
[0060] FIG. 12 schematically shows a block diagram according to
Embodiment 6; and
[0061] FIGS. 13A and 13B are cross-sectional views of Embodiment 7,
respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0062] The preferred Embodiment Modes and Embodiments are described
below.
EMBODIMENT MODE
Embodiment Mode 1
[0063] An top emission type light emitting device according to the
invention will be described with reference to FIGS. 1A and 1B.
[0064] FIG. 1A is a cross-sectional view of a part of a pixel
portion. FIG. 1B is a simplified view of a laminate constitution in
a light emitting region whereupon luminescence is discharged in a
direction which an arrow indicates. As for a configuration of light
emitting region, namely, a configuration of pixel electrodes, a
stripe arrangement, a delta arrangement, a mosaic arrangement and
the like are mentioned.
[0065] In FIG. 1A, reference numeral 300 denotes a first substrate;
reference numerals 301a, 301b, and 301c each designate insulating
layers; reference numeral 302 denotes a TFT; reference numeral 308
denotes a first electrode; reference numeral 309 denotes an
insulating material; reference numeral 310 denotes an EL layer;
reference numeral 311 denotes a second electrode; reference numeral
312 denotes a transparent protective laminate; reference numeral
313 denotes a second sealing material; and reference numeral 314
denotes a second substrate.
[0066] The TFT 302 (p-channel type TFT) provided over the first
substrate 300 is an element which controls an electric current
flowing into a luminescent EL layer 310. Further, reference numeral
304 denotes a drain region (or source region); and reference
numeral 306 denotes a drain electrode (or source electrode) which
connects the first electrode to the drain region (or source
region). Still further, in a same process as in the drain electrode
306, a wiring 307 such as a power supply wiring and a source wiring
is simultaneously formed. An example in which the first electrode
and the drain electrode are separately formed is described in the
present Embodiment Mode; however, these electrodes may be a same
one. An insulating layer 301a to be an undercoat insulating film (a
lower layer thereof and an upper layer thereof are herein referred
to as a nitride insulating film and an oxidized insulating film,
respectively) is formed on the first substrate 300, while a gate
insulating film is provided between a gate electrode 305 and an
active layer. Further, reference numeral 301b denotes an interlayer
insulating film comprising an organic material or an inorganic
material; and reference numeral 301c denotes an interlayer
insulating film comprising an inorganic insulating film. Still
further, although not shown here, another TFT (n-channel type TFT
or p-channel type TFT) or a plurality of TFTs are provided per
pixel. TFT having one channel-forming region 303 is described in
the present Embodiment Mode; however, TFT is not limited to this
type and TFT may have a plurality of channels.
[0067] Reference numeral 308 denotes the first electrode, that is,
an anode (or cathode) of a light emitting element. As for a
material of the first electrode 308, a film or a laminate film
which comprises an element selected from the group consisting of:
Ti, TiN, TiSi.sub.XN.sub.Y, Ni, W, WSi.sub.X, WN.sub.X,
WSi.sub.XN.sub.Y, NbN, Cr, Pt, Zn, Sn, In and Mo, or an alloy
material or a compound material comprising any one of
above-selected elements as a primary component, may be used in the
range of from 100 nm to 800 nm as an entire film thickness. A
titanium nitride film is used as the first electrode 308 in the
present Embodiment Mode. When the titanium nitride film is used as
the first electrode 308, it is preferable that a work function is
allowed to be increased by subjecting a surface to a plasma
treatment by means of a chlorine gas or to ultraviolet ray
irradiation.
[0068] Further, an insulating material 309 (referred to also as a
bank, a partition, a barrier, a mound or the like) which covers an
edge of the first electrode 308 (and wiring 307) is provided. As
for the insulating material 309, an inorganic material (for
example, silicon oxide, silicon nitride, or silicon oxynitride), a
photosensitive or non-photosensitive organic material (for example,
polyimide, an acrylic resin, polyamide, polyimidoamide, resist or
benzocyclobutene), a laminate of these materials, or the like can
be used; however, a photosensitive organic resin covered with a
silicon nitride film is used in the present Embodiment Mode. For
example, when a positive type photosensitive acrylic resin is used
as an organic resin material, it is preferable that only an upper
edge portion of the insulating material is allowed to have a curved
surface having a curvature radius. Further, as for the insulating
material, either a negative type which becomes insoluble to an
etchant by photosensitive light or a positive type which becomes
soluble to the etchant by the light can be used.
[0069] A layer 310 containing an organic compound is formed by
using vapor deposition or coating. For the purpose of improving
reliability, it is preferable that deaeration is performed by
vacuum heating (100.degree. C. to 250.degree. C.) immediately
before the layer 310 containing the organic compound is formed. For
example, when vapor deposition is used, such vapor deposition is
performed in a film-forming chamber which is evacuated to a vacuum
state up to a degree of vacuum of 5.times.10.sup.-3 Torr (0.665
Pa), preferably in the range of from 10.sup.-4 Torr to 10.sup.-6
Torr. At the vapor deposition process, the organic compound is
previously vaporized by resistant heating, and when a shutter is
opened at the vapor deposition, the vaporized organic compound is
scattered in the direction of a substrate. The vaporized organic
compound then flies upward, and is vapor deposited over the
substrate through an opening provided on a metal mask.
[0070] For example, a white color can be obtained by laminating
Alq.sub.3, Alq.sub.3 partially doped with Nile Red which is a
red-color luminescent pigment, p-EtTAZ, and TPD (aromatic diamine)
in order by vapor deposition.
[0071] Further, when a layer containing an organic compound is
formed by coating using spin coating, it is preferable that the
layer, after being applied, is baked by vacuum heating. For
example, an aqueous solution of poly (ethylene dioxythiophene)/poly
(styrene sulfonic acid) (referred to also as PEDOT/PSS) which will
acts as a hole injection layer is applied on an entire surface of
the substrate, and baked. On the resultant substrate, thereafter, a
polyvinyl carbazole (referred to also as PVK) solution doped with a
luminescence center pigment (for example,
1,1,4,4-tetraphenyl-1,3-butadiene (TPB),
4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran
(DCM 1), Nile Red, or coumarin 6) which will act as a light
emitting layer may be applied, and then, baked. Further, PEDOT/PSS
uses water as a solvent and is not soluble in an organic solvent.
Therefore, when PVK is applied thereover, there is no fear of being
dissolved again. Since PEDOT/PSS and PVK employ different solvents
from each other, it is preferable that a same film-forming chamber
is not shared. Still further, the layer 310 containing the organic
compound can be prepared as a single layer, and a 1,3,4-oxadiazole
derivative (PBD) having an electron transport property may be
dispersed in polyvinyl carbazole (PVK) having a hole transport
property. Furthermore, 30% by weight of PBD is dispersed therein as
an electron transport agent and, then, an appropriate quantity of
each of 4 types of pigments (TPB, coumarin 6, DCM 1, and Nile Red)
is dispersed to obtain white luminescence.
[0072] Although an example of a light emitting element for
obtaining white luminescence has been described above, it goes
without saying that a light emitting element which can obtain red
luminescence, green luminescence, or blue luminescence can be
fabricated by appropriately selecting materials of the layer 310
containing the organic compound.
[0073] Reference numeral 311 denotes a second electrode comprising
an electrically conductive layer, that is, a cathode (or anode) of
a light emitting element. As for materials for the second electrode
311, an alloy selected from the group consisting of: MgAg, MgIn,
AlLi, CaF.sub.2, CaN, and the like, or a translucent film formed by
using an element belonging to the group I or II in the periodic
table, and aluminum by means of co-vapor deposition may be used.
Since an top emission type in which light emission is performed by
allowing luminescence to pass through the second electrode is
adopted in the present Embodiment Mode, an aluminum film having a
thickness of from 1 nm to 10 nm, or an aluminum film comprising a
trace quantity of Li is used. In a constitution in which the
aluminum film is used as the second electrode 311, it becomes
possible to form a material adjacent to the layer 310 containing
the organic compound by a material other than oxides whereupon
reliability of the light emitting device can be improved. It is
also permissible that a translucent layer (thickness being from 1
nm to 5 nm) comprising CaF.sub.2, MgF.sub.2, or BaF.sub.2 may be
also formed as a cathode buffer layer before the aluminum layer
having a thickness of from 1 nm to 10 nm is formed.
[0074] For the purpose of reducing resistance of the cathode, the
cathode 311 may have a laminate constitution comprising a metal
thin film having a thickness of from 1 nm to 10 nm, and a
transparent conductive layer (for example, indium oxide-tin oxide
alloy (ITO), indium oxide-zinc oxide alloy (In.sub.2O.sub.3--ZnO),
or zinc oxide (ZnO)). In another case, for the same purpose, an
auxiliary electrode may be provided in a region which is not a
light emitting region over the second electrode 311. Further, the
cathode may be selectively formed by using vapor deposition mask by
means of a resistance heating employing vapor deposition
technique.
[0075] Reference numeral 312 denotes a transparent protective
laminate to be formed by sputtering or vapor deposition and the
layer becomes a sealing film which not only protects the second
electrode 311 comprising a metal thin film but also prevents
penetration of moisture. As shown in FIG. 1B, the transparent
protective laminate 312 comprises a laminate comprising an
inorganic insulating film 312a, a stress relaxing film 312b, and an
inorganic insulating film 312c. As for the inorganic insulating
film 312a, at least one film selected from the group consisting of:
a silicon nitride film, a silicon oxide film, a silicon oxynitride
film (SiNO film (component ratio: N>O), or SiON film (component
ratio: N<O)), and a thin film containing carbon as a primary
component (for example, DLC film, or CN film) which are obtained by
sputtering or CVD can be used. These inorganic insulating films
312a each have a high blocking effect against moisture; however, as
film thickness thereof is increased, a film stress is increased,
and therein, they tend to be partially peeled or totally removed as
a film. Nevertheless, stress can be relaxed and moisture can be
absorbed by sandwiching the stress relaxing film 312b between the
inorganic insulating film 312a and the inorganic insulating film
312c. Even when a minute hole (pinhole or the like) is formed in
the inorganic insulating film 312a by an undefined reason, the
minute hole can be blocked by the stress relaxing film 312b, and
further, by providing the inorganic insulating film 312c thereover,
an extremely high blocking effect against moisture or oxygen can be
attained.
[0076] As for materials for the stress relaxing film 312b, a
material which has smaller stress than the inorganic insulating
films 312a and 312c and has a hygroscopic property is preferable.
In addition to the above-described properties, a material having a
translucent property is desirable. Further, as for the stress
relaxing film 312b, a material film containing an organic compound
such as .alpha.-NPD
(4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl), BCP
(bathocuproin), MTDATA
(4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine), and
Alq.sub.a (a tris-8-quinolinolate aluminum complex) may be used.
These material films each have a hygroscopic property. Also, they
are nearly transparent when they are thin in thickness. When they
become thin in thickness, they become nearly transparent. Since
MgO, SrO.sub.2, and SrO each have a hygroscopic property and
translucency and, also, a thin film thereof can be obtained by
vapor deposition, any one of these oxides can be used as the stress
relaxing film 312b.
[0077] Further, as for the stress relaxing film 312b, a same
material used in a layer, containing an organic compound, which is
sandwiched between the cathode and the anode can also be used.
[0078] In a case in which it is possible to form the inorganic
insulating films 312a and 312c by sputtering (or CVD) and the
stress relaxing film 312b by vapor deposition, a substrate is
transported back and forth between a vapor-depositing chamber and a
sputtering film-forming chamber (or CVD film-forming chamber)
whereupon it is a merit that there is no need of providing another
film-forming chamber. Although it is conceivable to use an organic
resin film as the stress relaxing film, since the organic resin
film contains a solvent, it is necessary to subject the organic
resin film to a baking treatment, therefore, there are problems
such as an increase of a number of production steps, contamination
by a solvent component, damage by baking heat, and a necessity of
degasification.
[0079] The thus-formed transparent protective laminate 312 is
optimum as a sealing film of a light emitting element which
comprises a light emitting layer containing an organic compound.
Since the transparent protective laminate 312 has a hygroscopic
property, it also functions as removing moisture.
[0080] The second sealing material 313 bonds the second substrate
314 and the first substrate 300. The first sealing material (not
shown), which comprises a gap material for securing a space between
the substrates, is arranged such that it surrounds the second
sealing material 313. The second sealing material 313 is not
particularly limited so long as it is translucent. As an
illustrative example, an epoxy resin curable by an ultraviolet ray
or by heat may be used. In the present Embodiment Mode, used is a
high heat-resistant UV epoxy resin (2500 Clear; available from
Electro-lite Corporation) having a refractive index of 1.50, a
viscosity of 500 cps, a Shore-D hardness of 90, a tensile strength
of 3000 psi, a Tg point of 150.degree. C., a volume resistance of
1.times.10.sup.15 .OMEGA.cm, and an electric strength of 450 V/mil.
It is possible to improve an entire light transmittance by filling
a gap between a pair of substrates with the second sealing material
313 compared with a case in which the gap between the pair of
substrates is a space (inert gas).
Embodiment Mode 2
[0081] An example in which a plastic substrate is used as a second
substrate and a transparent protective layer is provided over the
substrate is shown in FIGS. 2A and 2B. Since the example shown in
FIGS. 2A and 2B are constituted in a same manner as in FIGS. 1A and
1B except for the second substrate, same reference numerals are
applied to parts identical to those in FIGS. 1A and 1B.
[0082] As for the second substrate 414, a plastic substrate
comprising at least one member selected from the group consisting
of: polyethylene terephthalate (PET), polyether sulfone (PES),
polyethylene naphthalate (PEN), polycarbonate (PC), nylon,
polyether etherketone (PEEK), polysulfone (PSF), polyether imide
(PEI), polyallylate (PAR), polybutylene terephthalate (PBT), and
polyimide may be used.
[0083] A transparent protective laminate 412 similar to the
transparent protective laminate 312 as shown in Embodiment Mode 1
is formed over the second substrate 414.
[0084] The transparent protective laminate 412 is a transparent
protective laminate which is formed by sputtering or vapor
deposition and becomes a sealing film for preventing penetration of
moisture. As shown in FIG. 2B, the transparent protective laminate
412 is a laminate comprising an inorganic insulating film 412c, a
stress relaxing film 412b, and an inorganic insulating film 412a.
As for the inorganic insulating film 412c, at least one film
selected from the group consisting of: a silicon nitride film, a
silicon oxide film, a silicon oxynitride film (SiNO film (component
ratio: N>O), or SiON film (component ratio: N<O)) and a thin
film containing carbon as a primary component (for example, DLC
film, or CN film) which are obtained by sputtering or CVD can be
used. These inorganic insulating films each have a high blocking
effect against moisture; however, as film thickness thereof is
increased, a film stress is increased, then they tend to be
partially peeled or totally removed as a film. Nevertheless, stress
can be relaxed and, also, moisture can be absorbed by sandwiching
the stress relaxing film 412b between the inorganic insulating film
412a and the inorganic insulating film 412c. Even when a minute
hole (pinhole or the like) is formed in the inorganic insulating
film 412c by an undefined reason, the minute hole can be blocked by
the stress relaxing film 412b and, further, by providing the
inorganic insulating film 412a thereover, an extremely high
blocking effect against moisture or oxygen can be attained.
[0085] As for materials for the stress relaxing film 412b, a
material which has smaller stress than the inorganic insulating
films 412a and 412c and has a hygroscopic property is preferable.
In addition to the above-described properties a material having a
translucent property is desirable. Further, as for the stress
relaxing film 412b, a material film containing an organic compound
such as .alpha.-NPD
(4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl), BCP
(bathocuproin), MTDATA
(4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine), and
Alq.sub.a (a tris-8-quinolinolate aluminum complex) may be used.
These material films each have a hygroscopic property. Also, they
are nearly transparent when they are thin in thickness. Since MgO,
SrO.sub.2, and SrO each have a hygroscopic property and
translucency, and also, a thin film thereof can be obtained by
vapor deposition, any one of these oxides can be used as the stress
relaxing film 412b.
[0086] The second substrate 414 on which the transparent protective
laminate 412 is thus formed is optimum as a sealed substrate of a
light emitting element which comprises a light emitting layer
containing an organic compound. Since the transparent protective
laminate 412 has a hygroscopic property, it also functions as
removing moisture.
Embodiment Mode 3
[0087] A bottom emission type light emitting device according to
the present invention will be described with reference to FIGS. 3A
and 3B.
[0088] FIG. 3A is a view showing a cross-section of a part of a
pixel portion. Further, FIG. 3B is a simplified view of a laminate
constitution in a light emitting region whereupon luminescence is
discharged in a direction which an arrow indicates.
[0089] In FIG. 3A, reference numeral 500 denotes a first substrate;
reference numerals 501a, 501b, and 501c each designate an
insulating layer; reference numeral 502 denotes a TFT; reference
numeral 508 denotes a first electrode; reference numeral 509
denotes an insulating material; reference numeral 510 denotes an EL
layer; reference numeral 511 denotes a second electrode; reference
numeral 512 denotes a protective laminate; reference numeral 513
denotes a space (inert gas); and reference numeral 514 denotes a
second substrate.
[0090] The TFT 502 (p-channel type TFT) provided over the first
substrate 500 is an element which controls an electric current
flowing into a EL layer 510. Further, reference numeral 504 denotes
a drain region (or a source region); and reference numeral 506
denotes a drain electrode (or a source electrode) which connects
the first electrode to the drain region (or the source region).
Still further, in a same process as in the drain electrode 506, a
wiring 507 such as a power supply wiring and a source wiring is
simultaneously formed. An example in which the first electrode and
the drain electrode are separately formed is shown in the present
Embodiment Mode; however, these electrodes may be a same one. An
insulating layer 501a to be an undercoat insulating film (a lower
layer thereof and an upper layer thereof are herein referred to as
a nitride insulating film and an oxidized insulating film,
respectively) is formed over the first substrate 500, while a gate
insulating film is provided between a gate electrode 505 and an
active layer. Further, reference numeral 501b denotes an interlayer
insulating film comprising an organic material or an inorganic
material, while reference numeral 501c denotes an interlayer
insulating film comprising an inorganic insulating film. Still
further, although not shown here, another TFT (n-channel type TFT
or p-channel type TFT) or a plurality of TFTs are provided per
pixel. Furthermore, TFT having one channel-forming region 503 is
shown in the present Embodiment Mode; however, TFT is not limited
to this type and TFT may have a plurality of channels.
[0091] Reference numeral 508 denotes the first electrode, that is,
an anode (or a cathode) of a light emitting element. As for
materials for the first electrode 508, a transparent electrically
conductive film (for example, an indium oxide-tin oxide alloy
(ITO), an indium oxide-zinc oxide alloy (In.sub.2O.sub.3--ZnO), or
zinc oxide (ZnO)) may be used.
[0092] Further, an insulating material 509 (referred to also as a
bank, a partition, a barrier, a mound or the like) which covers an
edge portion of the first electrode 508 (and wiring 507) is
provided.
[0093] The layer 510 containing an organic compound is formed by
vapor deposition or coating.
[0094] For example, a green color can be obtained by laminating
CuPc (20 nm), .alpha.-NPD (60 nm), Alq.sub.3 doped with DMQA (37.5
nm), and Alq.sub.a (37.5 nm) in order by vapor deposition.
[0095] Reference numeral 511 denotes a second electrode comprising
an conductive film, that is, a cathode (or anode) of a light
emitting element. As for materials for the second electrode 511, an
alloy selected from the group consisting of: MgAg, MgIn, AlLi,
CaF.sub.2, CaN, and the like, or a film formed by using an element
belonging to the group I or II in the periodic table and aluminum
by means of co-vapor deposition may be used.
[0096] Reference numeral 512 denotes a protective laminate to be
formed by sputtering or vapor deposition and the layer becomes a
sealing film which not only protects the second electrode 511
comprising a metal film but also prevents penetration of moisture.
Different from Embodiment Mode 1, since Embodiment Mode 2 is a
bottom emission type, the protective laminate 512 is not
necessarily transparent. As shown in FIG. 3B, the protective
laminate 512 comprises a laminate comprising an inorganic
insulating film 512a, a stress relaxing film 512b, and an inorganic
insulating film 512c. As for the inorganic insulating film 512a, at
least one film selected from the group consisting of: a silicon
nitride film, a silicon oxide film, a silicon oxynitride film (SiNO
film (component ratio: N>O), or SiON film (component ratio:
N<O)), and a thin film containing carbon as a primary component
(for example, DLC film, or CN film) which are obtained by
sputtering or CVD can be used. These inorganic insulating films
512a each have a high blocking effect against moisture; however, as
film thickness thereof is increased, a film stress is increased,
and therein, they tend to be partially peeled or totally removed as
a film. Nevertheless, stress can be relaxed, and moisture can be
absorbed by sandwiching the stress relaxing film 512b between the
inorganic insulating film 512a and the inorganic insulating film
512c. Even when a minute hole (pinhole or the like) is formed in
the inorganic insulating film 512a by an undefined reason, the
minute hole can be blocked by the stress relaxing film 512b, and
further, by providing the inorganic insulating film 512c thereover,
an extremely high blocking effect against moisture or oxygen can be
attained.
[0097] As for materials for the stress relaxing film 512b, a
material which has smaller stress than the inorganic insulating
films 512a and 512c and has a hygroscopic property is preferable.
As for the stress relaxing film 512b, a material film containing an
organic compound such as .alpha.-NPD
(4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl), BCP
(bathocuproin), MTDATA
(4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine), and
Alq.sub.3 (a tris-8-quinolinolate aluminum complex) may be used.
Since MgO, SrO.sub.2, and SrO each have a hygroscopic property and
a thin film thereof can be obtained by vapor deposition, any one of
these oxides can be used as the stress relaxing film 512b.
[0098] Further, as for the stress relaxing film 512b, a same
material used in a layer containing an organic compound, which is
sandwiched between the cathode and the anode can also be used.
[0099] In a case in which it is possible to form the inorganic
insulating films 512a and 512c by sputtering (or CVD) and the
stress relaxing film 512b by vapor deposition, a substrate is
transported back and forth between a vapor-depositing chamber and a
sputtering film-forming chamber (or CVD film-forming chamber)
whereupon it is a merit that there is no need of providing another
film-forming chamber. Although it is conceivable to use an organic
resin film as the stress relaxing film, since the organic resin
film contains a solvent, it is necessary to subject the organic
resin film to a baking treatment, therefore, there are problems
such as an increase of a number of production steps, contamination
by a solvent component, damage by baking heat, and a necessity of
degasification.
[0100] The thus-formed protective laminate 512 is optimum as a
sealing film of a light emitting element which comprises a light
emitting layer containing an organic compound. Since the protective
laminate 512 has a hygroscopic property, it also functions as
removing moisture.
[0101] The sealing material (not shown), comprising a gap material
for securing a space between the substrates, bonds the second
substrate 514 to the first substrate 500. Further, in a space
between the pair of substrates is filled with an inert gas (for
example, nitrogen gas). Still further, a desiccant may optionally
be arranged over the second substrate for removing a trace quantity
of moisture in the space 513.
EMBODIMENTS
Embodiment 1
[0102] In FIG. 4A, shown is an example of manufacturing a light
emitting device (having an top emission constitution) provided over
a substrate having an insulating surface with a light emitting
element in which an organic compound layer is allowed to be a light
emitting layer.
[0103] FIG. 4A is a top view of the light emitting device, while
FIG. 4B is a cross-sectional view taken along a line A-A' in FIG.
4A. Reference numeral 1101 indicated by a dotted line denotes a
source signal line driver circuit; reference numeral 1102 denotes a
pixel portion; and reference numeral 1103 denotes a gate signal
line driver circuit. Further, reference numeral 1104 denotes a
transparent sealed substrate; reference numeral 1105 denotes a
first sealing material; and reference numeral 1107 denotes a
transparent second sealing material which fills an inside of an
area surrounded by the first sealing material 1105. The first
sealing material 1105 contains a gap material for securing a space
between substrates.
[0104] Reference number 1108 denotes a wiring for transmitting a
signal to be inputted to the source signal line driver circuit 1101
and the gate signal line driver circuit 1103. The wiring 1108
receives a video signal or a clock signal from a flexible print
circuit (FPC) 1109 which becomes an external input terminal.
Although only the FPC 1109 is shown, a printed wiring board (PWB)
may be attached to the FPC 1109.
[0105] Subsequently, a sectional constitution will be described
with reference to FIG. 4B. A driver circuit and a pixel portion are
formed over a substrate 1110, but the source signal line driver
circuit 1101 as the driver circuit and the pixel portion 1102 are
shown in FIG. 4B.
[0106] In the source signal line driver circuit 1101, a CMOS
circuit in which an n-channel type TFT 1123 and a p-channel type
TFT 1124 are combined is formed. The TFT which constitutes the
driver circuit may be formed by at least one circuit selected from
the group consisting of: a CMOS circuit, a PMOS circuit and an NMOS
circuit which are publicly known in the art. In the present
embodiment, a driver-integrated type in which the driver circuit is
formed over the substrate is shown, but the driver-integrated type
may not necessarily be adopted. The driver circuit can also be
formed outside instead of being formed over the substrate. A
constitution of the TFT using a polysilicon film as an active layer
is not particularly limited thereto, either a top gate type TFT or
a bottom gate type TFT is permissible.
[0107] The pixel portion 1102 is formed by a plurality of pixels
each of which comprises a switching TFT 1111, a current-controlling
TFT 1112 and a first electrode (anode) 1113 which is electrically
connected to the drain of the current-controlling TFT 1112. The
current-controlling TFT 1112 may either be an n-channel type TFT or
a p-channel type TFT, but when it is to be connected to the anode,
it is preferably the p-channel type TFT. It is also preferable that
a storage capacitor (not shown) is appropriately provided. An
example in which only a cross-sectional constitution of one pixel
is shown where two TFTs are used in the pixel is illustrated, but
three or more TFTs may appropriately be used per pixel.
[0108] Since it is constituted such that the first electrode 1113
is directly connected to the drain of the TFT 1112, it is
preferable that a lower layer of the first electrode 1113 is
allowed to be a material layer which can have an ohmic contact with
the drain comprising silicon, while an uppermost layer thereof
which contacts a layer containing an organic compound is allowed to
be a material layer which has a large work function. For example, a
three-layer constitution contained of a titanium nitride film, a
film containing aluminum as a primary component, and a titanium
nitride film, can have a low resistance of wiring, a favorable
ohmic contact, and also, can function as an anode. Further, as the
first electrode 1113, a monolayer of at least one film selected
from the group consisting of: a titanium nitride film, a chromium
film, a tungsten film, a zinc film, a platinum film and the like,
or a laminate of three layers or more may be used.
[0109] An insulating substance 1114 (referred to as a bank, a
partition, a barrier, a mound or the like) is formed over each end
of the first electrode (anode) 1113. The insulating substance 1114
may be formed by either an organic resin film or an insulating film
comprising silicon. In the present embodiment, as for the
insulating substance 1114, an insulating substance is formed in a
shape as shown in FIG. 4B by using a positive type photosensitive
acrylic resin film.
[0110] For the purpose of enhancing a coverage effect, a curved
surface having a curvature is to be formed in an upper end portion
or a lower end portion of the insulating substance 1114. For
example, when the positive type photosensitive acrylic resin is
used as a material for the insulating substance 1114, it is
preferable that a curved face having a curvature radius (0.2 .mu.m
to 3 .mu.m) is provided only to the upper end portion of the
insulating substance 1114. As for the insulating substance 1114,
either one of a negative type which becomes insoluble to an etchant
by photosensitive light, and a positive type which becomes soluble
to the etchant by the light can be used.
[0111] Further, the insulating substance 1114 may be covered by a
protective film comprising at least one film selected from the
group consisting of: an aluminum nitride film, an aluminum
oxynitride film, a thin film containing carbon as a primary
component, and a silicon nitride film.
[0112] A layer 1115 containing an organic compound is selectively
formed over the first electrode (anode) 1113 by vapor deposition
using vapor mask or inkjet. Further, a second electrode (cathode)
1116 is formed over the layer 1115 containing the organic compound.
As for the cathode, a material having a small work function (for
example Al, Ag, Li, Ca, alloys of thereof, that is, MgAg, MgIn,
AlLi, CaF.sub.2, or CaN) may be used. In the present embodiment, in
order to allow luminescence to pass through, as for the second
electrode (cathode) 1116, a laminate of a metal thin film which is
thin in thickness, and a transparent conductive film (for example,
an indium oxide-tin oxide alloy (ITO), an indium oxide-zinc oxide
alloy (In.sub.2O.sub.3--ZnO), or zinc oxide (ZnO)) is used. Then, a
light emitting element 1118 comprising the first electrode (anode)
1113, the layer 1115 containing the organic compound, and the
second electrode (cathode) 1116 is fabricated. In the present
embodiment, the light emitting element 1118 is allowed to be an
example of emitting white light, and therein, a color filter (for
the purpose of simplicity, an overcoat layer is not shown)
comprising a colored layer 1131 and a light blocking layer (BM)
1132 is provided.
[0113] Further, when layers each containing an organic compound
which can obtain R, G, and B luminescence respectively, are
selectively formed, a full-color display can be obtained without
using a color filter.
[0114] A transparent protective layer 1117 is formed in order to
seal the light emitting element 1118. As for the transparent
protective layer 1117, the transparent protective laminate shown in
Embodiment Mode 1 can be adopted. The transparent protective
laminate comprises a laminate comprising a first inorganic
insulating film, a stress relaxing film and a second inorganic
insulating film. As for each of the first and second inorganic
insulating films, at least one film selected from the group
consisting of: a silicon nitride film, a silicon oxide film, a
silicon oxynitride film (SiNO film (component ratio: N>O), or
SiON film (component ratio: N<O)), and a thin film containing
carbon as a primary component (for example, DLC film, or CN film)
which are obtained by sputtering or CVD can be used. These
inorganic insulating films each have a high blocking effect against
moisture; however, as film thickness thereof is increased, a film
stress is increased, then, they tend to be partially peeled or
totally removed as a film. Nevertheless, stress can be relaxed and,
also, moisture can be absorbed by sandwiching the stress relaxing
film between the first inorganic insulating film and the second
inorganic insulating film. Even when a minute hole (pinhole or the
like) is formed in the first inorganic insulating film by an
undefined reason, the minute hole can be blocked by the stress
relaxing film and, further, by providing the second inorganic
insulating film thereover, an extremely high blocking effect
against moisture or oxygen can be attained. As for materials for
the stress relaxing film, a material which has smaller stress than
the inorganic insulating films and has a hygroscopic property is
preferable. In addition to the above-described properties, a
material having a translucent property is desirable. Further, as
for the stress relaxing film, a material film containing an organic
compound such as .alpha.-NPD
(4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl), BCP
(bathocuproin), MTDATA
(4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine, and
Alq.sub.3 (a tris-8-quinolinolate aluminum complex) may be used.
These material films each have a hygroscopic property. When they
are thin in thickness, they become nearly transparent. Since MgO,
SrO.sub.2, and SrO each have a hygroscopic property and
translucency, and also, a thin film thereof can be obtained by
vapor deposition, any one of these oxides can be used as the stress
relaxing film. In the present embodiment, a silicon target is used,
a film formed in an atmosphere containing a nitrogen gas and an
argon gas, that is, a silicon nitride film having a high blocking
effect against impurities such as moisture, and an alkali metal is
used as the first inorganic insulating film or the second inorganic
insulating film, and a thin film of Alq.sub.3 formed by vapor
deposition is used as the stress relaxing film. Further, in order
to allow luminescence to penetrate the transparent protective
laminate, it is preferable that an entire film thickness of the
transparent protective laminate is formed as thin as possible.
[0115] Further, in order to seal the light emitting element 1118,
the sealed substrate 1104 is bonded thereto by using the first
sealing material 1105 and the second sealing material 1107 in an
inert gas atmosphere. As for the first sealing material 1105 and
the second sealing material 1107, it is preferable that an epoxy
resin is used. It is also preferable that the first sealing
material and the second sealing material are each made of a
material which does not allow moisture or oxygen to penetrate
thereinto as much as possible.
[0116] Further, in the present embodiment, a plastic substrate
comprising at least one member consisting of: fiberglass-reinforced
plastics (FRP), polyvinylfluoride (PVF), Mylar, polyester, an
acrylic resin, and the like, other than a glass substrate or a
quartz substrate can be used as a material which constitutes the
sealed substrate 1104. After the sealed substrate 1104 was bonded
by using the first sealing material 1105 and the second sealing
material 1107, it is possible to perform sealing by using a third
sealing material such that a side face (exposed face) is
covered.
[0117] By sealing the light emitting element by using the
transparent protective layer 1117, the first sealing material 1105,
and the second sealing material 1107 as described above, the light
emitting element can thoroughly be shielded from outside. In
consequence, substance, such as moisture and oxygen, which will
deteriorate the organic compound layer can be prevented from
entering from outside. Accordingly, a light emitting device having
high reliability can be obtained.
[0118] Further, as for the first electrode 1113, a both-side
emission type light emitting device can be prepared by using a
transparent conductive film.
[0119] In the present embodiment, an example of a constitution
(hereinafter, referred top emission constitution) in which a layer
containing an organic compound is formed over an anode and a
cathode which is a transparent electrode is formed over the layer
containing the organic compound was shown; however, a constitution
having a light emitting element (hereinafter, bottom emission
constitution) in which an organic compound is formed over an anode
and a cathode is formed over the organic compound, and then
luminescence generated in the layer containing the organic compound
is drawn from the anode which is a transparent electrode to TFT,
may also be permissible.
[0120] An example of a light emitting device having a bottom
emission constitution is shown in FIGS. 5A and 5B.
[0121] FIG. 5A is a top view of the light emitting device, while
FIG. 5B is a cross-sectional view taken along a line A-A' in FIG.
5A. Reference numeral 1201 indicated by a dotted line denotes a
source signal line driver circuit; reference numeral 1202 denotes a
pixel portion; and reference numeral 1203 denotes a gate signal
line driver circuit. Further, reference numeral 1204 denotes a
sealed substrate; reference numeral 1205 denotes a sealing material
in which a gap material for securing a sealed space is contained;
and an inside of an area surrounded by the sealing material 1205 is
filled with an inert gas (illustratively, a nitrogen gas). A trace
quantity of moisture present in the space inside the area
surrounded by the sealing material 1205 is removed by a desiccant
1207 and, accordingly, the space is sufficiently dry.
[0122] Reference number 1208 denotes a wiring for transmitting a
signal to be inputted to the source signal line driver circuit 1201
and the gate signal line driver circuit 1203. The wiring 1208
receives a video signal or a clock signal from a flexible print
circuit (FPC) 1209 which becomes an external input terminal.
[0123] Subsequently, a sectional constitution will be described
with reference to FIG. 5B. A driver circuit and a pixel portion are
formed on a substrate 1210, but the source signal line driver
circuit 1201 as the driver circuit and the pixel portion 1202 are
shown in FIG. 5B. In the source signal line driver circuit 1201, a
CMOS circuit in which an n-channel type TFT 1223 and a p-channel
type TFT 1224 are combined is formed.
[0124] The pixel portion 1202 is formed by a plurality of pixels
each of which comprises a switching TFT 1211, a current-controlling
TFT 1212 and a first electrode (anode) 1213 comprising a
transparent conductive film which is electrically connected to a
drain of the current-controlling TFT 1212.
[0125] In the present embodiment, it is constituted such that the
first electrode 1213 is formed such that a part thereof is
overlapped with a connecting electrode and the first electrode 1213
is electrically connected to a drain region of the TFT 1212 via a
connecting electrode. It is preferable that the first electrode
1213 has transparency and comprises an electrically conductive film
having a large work function (for example, an indium oxide-tin
oxide alloy (ITO), an indium oxide-zinc oxide alloy
(In.sub.2O.sub.3--ZnO), or zinc oxide (ZnO)).
[0126] An insulating substance 1214 (referred to as a bank, a
partition, a barrier, a mound or the like) is formed over each end
of the first electrode (anode) 1213. For the purpose of enhancing a
coverage effect, a curved surface having a curvature is allowed to
be formed in an upper end portion or a lower end portion of the
insulating substance 1214. Further, the insulating substance 1214
may be covered by a protective film comprising at least one film
selected from the group consisting of: an aluminum nitride film, an
aluminum oxynitride film, a thin film containing carbon as a
primary component, and a silicon nitride film.
[0127] A layer 1215 containing an organic compound is selectively
formed over the first electrode (anode) 1213 by vapor deposition
using a vapor deposition mask or inkjetting. Further, a second
electrode (cathode) 1216 is formed over the layer 1215 containing
the organic compound. As for the cathode, a material having a small
work function (for example Al, Ag, Li, Ca, alloys of thereof, that
is, MgAg, MgIn, AlLi, CaF.sub.2, or CaN) may be used. Then, a light
emitting element 1218 comprising the first electrode (anode) 1213,
the layer 1215 containing the organic compound, and the second
electrode (cathode) 1216 is fabricated. The light emitting element
1218 emits light in a direction which an arrow in FIG. 5B
indicates. The light emitting element 1218 in the present
embodiment is one type of light emitting element which can obtain
mono-color luminescence of R, G, or B. Three of such light emitting
elements as described above, in each of which a layer containing an
organic compound capable of obtaining one of R, G, and B
luminescence is selectively formed, are combined to obtain
full-color luminescence.
[0128] Further, a protective layer 1217 is formed in order to seal
the light emitting element 1218. As for the protective layer 1217,
the protective laminate shown in Embodiment Mode 2 can be adopted.
The protective laminate comprises a laminate comprising a first
inorganic insulating film, a stress relaxing film and a second
inorganic insulating film.
[0129] Further, in order to seal the light emitting element 1218,
the sealed substrate 1204 is bonded thereto by using the sealing
material 1205 in an inert gas atmosphere. A concave portion has
previously been formed over the sealed substrate 1204 by
sandblasting or the like and, then, a desiccant 1207 is bonded to
the thus-formed concave portion. As for the sealing material 1205,
it is preferable that an epoxy resin is used. It is also preferable
that the sealing material 1205 is composed of a material which does
not penetrate moisture or oxygen as much as possible.
[0130] Further, in the present embodiment, a plastic substrate
comprising at least one member selected from the group consisting
of: fiberglass-reinforced plastics (FRP), polyvinyl fluoride (PVF),
Mylar, polyester, an acrylic resin, and the like, other than a
metal substrate, a glass substrate or a quartz substrate can be
used as a material which constitutes the sealed substrate 1204
having the recess portion. It is also possible to perform sealing
by using a metal can in which a desiccant is bonded to an inside
thereof.
[0131] Further, the present embodiment can freely be combined with
any one of Embodiment Modes 1 to 3.
Embodiment 2
[0132] In the present embodiment, an example of a manufacturing
apparatus of a multi-chamber method, in which an entire process
from vapor deposition over a first electrode to sealing is
automated, is described with reference to FIG. 6.
[0133] FIG. 6 is a multi-chamber manufacturing apparatus that
includes: gates 100a to 100y; transport chambers 102, 104a, 108,
114, and 118; delivery chambers 105, 107, and 111; a load chamber
101; a first film-forming chamber 106H (EL layer: HTL, HIL); a
second film-forming chamber 106B (EL layer: B); a third
film-forming chamber 106G (EL layer: G); a fourth film-forming
chamber 106R (EL layer: R); a fifth film-forming chamber 106E (EL
layer: E); other film-forming chambers 109 (ITO or IZO film), 110
(metal film), 112 (spin coat or ink jet), 113 (SiN film or
SiO.sub.x film), and 132 (deposition of a layer containing an
organic compound), a setting chambers 126R, 126G, 126B, 126E, and
126H in each of which vapor deposition source is set; pretreatment
chambers 103a (bake or O.sub.2 plasma, H.sub.2 plasma, Ar plasma)
and 103b (vacuum bake); a sealing chamber 116; a mask stock chamber
124; a sealed substrate storage chamber 130; a cassette chambers
120a and 120b, a tray attachment stage 121; and a extraction
chamber 119. In the transport chamber 104a, a transport mechanism
104b is provided for transport a substrate 104c and in other
transport chambers, respective transport mechanisms are also
provided.
[0134] Hereinafter, a process comprising a step of bringing a
substrate over which an anode (first electrode), and an insulating
substance (partition) that covers an end portion of the anode have
previously been provided in a manufacturing apparatus as shown in
FIG. 6 and a step of fabricating a light emitting device is
described. When an active matrix type light emitting device is
manufactured, a thin film transistor (current-controlling TFT)
which is connected to an anode, a plurality of other thin film
transistors (for example, switching TFT) and a driver circuit
comprising another thin film transistor have previously been
provided over a substrate. Even when a passive matrix type light
emitting device is manufactured, the device can be manufactured by
using the manufacturing apparatus as shown in FIG. 6.
[0135] Firstly, the above-described substrate is set in the
cassette chamber 120a or the cassette chamber 120b. When the
substrate is large in size (for example, 300 mm.times.360 mm), it
is set in cassette chamber 120b, while, when the substrate is of an
normal size (for example, 127 mm.times.127 mm), it is set in the
cassette chamber 120a, and then, the thus-set substrate is
transported into the tray loading stage 121 where a plurality of
substrates are set on a tray (for example, 300 mm.times.360
mm).
[0136] The substrates (over which an anode and an insulating
substance that covers an end portion of the anode are formed) set
in either of the cassette chambers are, then, transported to the
transport chamber 118.
[0137] Before the substrates are set in either of the cassette
chambers, in order to reduce a spot defect, it is preferable that a
surface of the first electrode (anode) is cleaned by using a porous
sponge (for example, being made of polyvinyl alcohol (PVA), or
nylon) impregnated with a surfactant (being alkalescent), thereby
removing dust from a surface thereof. As for a cleaning mechanism,
a cleaning apparatus having a roll brush (for example, made of PVA)
which contacts a face of a substrate such that the roll brush
rotates around an axis line parallel to the face of the substrate
may be used, or another cleaning apparatus having a disk brush (for
example, made of PVA) which contacts a face of a substrate such
that the disk brush rotates around an axis line vertical to the
face of the substrate may be used. Further, before a film
containing an organic compound is formed, in order to remove
moisture or other gases contained in the substrate, it is
preferable that annealing for degasification is performed on the
substrate under vacuum. The substrate is transported into a bake
chamber (a pretreatment chamber) 123 connected to the transport
chamber 118, and then, such annealing may be performed in the bake
chamber 123.
[0138] Subsequently, the resultant substrate is transported from
the transport chamber 118, which is provided with a substrate
transport mechanism, into the load chamber 101. In the
manufacturing apparatus according to the present embodiment, the
load chamber 101 is provided with a substrate reversal mechanism
which can appropriately reverse the substrate. The load chamber 101
is connected to a vacuum-evacuation treatment chamber. It is
preferable that, after the load chamber 101 is evacuated to a
vacuum state, it allows an inert gas to be introduced thereinto,
thereby being at an atmospheric pressure.
[0139] Subsequently, the resultant substrate is transported into
the transport chamber 102 connected to the load chamber 101. It is
preferable that, in order to allow an inside of the transport
chamber 102 to be free from moisture or oxygen as much as possible,
the inside thereof is evacuated to a vacuum state such that the
vacuum state is maintained.
[0140] Further, the vacuum-evacuation treatment chamber is provided
with a magnetically floating type turbo-molecular pump, a
cryosorption pump, or a drypump. In such constitution, an ultimate
vacuum degree in the transport chamber 102 connected to the load
chamber 101 is allowed to be in the range of from 10.sup.-5 Pa to
10.sup.-6 Pa, and further, back diffusion of impurities from a pump
side and an exhaust system can be controlled. In order to prevent
the impurities from being introduced into inside the apparatus, as
for a gas to be introduced, an inert gas, for example, a nitrogen
gas, or a noble gas is used. Any one of these gases to be
introduced inside the apparatus is highly purified by a gas
purifier before it is introduced into inside the apparatus, and
then, used. Accordingly, it is necessary to provide the gas
purifier such that the gas is firstly highly purified, and then,
introduced into inside the vapor deposition apparatus. Under such
constitution, since oxygen, moisture, or any other impurities
contained in the gas can be removed in advance, these impurities
can be prevented from being introduced into inside the
apparatus.
[0141] Further, when it is desired that a film containing an
organic compound formed in an unnecessary part is removed, the
resultant substrate is transported into the pretreatment chamber
103a where the film containing the organic compound, then, may
selectively be removed. The pretreatment chamber 103a is provided
with a plasma-generating device in which a gas or a plurality of
gases of at least one element selected from the group consisting
of: Ar, H, F, and O are excited to generate plasma, and then, dry
etching is performed by the thus-generated plasma. Further, a UV
irradiation mechanism may be provided in the pretreatment chamber
103a such that an ultraviolet ray irradiation can be executed to
perform an anode surface treatment.
[0142] In order to be free from shrinkage, it is preferable that
vacuum heating is performed immediately before a film containing an
organic compound is formed by vapor deposition. The resultant
substrate is transported into the pretreatment chamber 103b where,
in order to thoroughly remove moisture, or any other gases
contained in the substrate, annealing for degasification is
performed on the substrate under vacuum (a degree thereof being
5.times.10.sup.-3 Torr (0.665 Pa) or less and, preferably, in the
range of from 10.sup.-4 Torr to 10.sup.-6 Torr). In the
pretreatment chamber 103b, a plate heater (sheath heater as a
typical example) is used to uniformly heat a plurality of
substrates. Particularly, when an organic resin film is used as a
material of an interlayer insulating film or a partition, an
organic resin material tends to absorb moisture depending on a type
thereof. Since there is a risk of degasification, it is effective
to perform vacuum heating for removing absorbed moisture before a
layer containing an organic compound is formed such that the
organic resin material is heated at a temperature in the range of
from 100.degree. C. to 250.degree. C., preferably in the range of
from 150.degree. C. to 200.degree. C., for example, for 30 minutes
or more, and then, the thus-heated organic resin material is left
to stand in air for spontaneous cooling.
[0143] Subsequently, after the above-described vacuum heating, the
resultant substrate is transported from the transport chamber 102
to the delivery chamber 105, and then, the substrate is transported
without being exposed to air from the delivery chamber 105 to the
transport chamber 104a.
[0144] Thereafter, the substrate is appropriately transported into
each of the film-forming chambers 106R, 106G, 106B, and 106E each
of which is connected to the transport chamber 104a. Over the
thus-transported substrate, a low molecular weight organic compound
layer which will become a hole injection layer, a hole transport
layer, a light emitting layer, an electron transport layer, or an
electron injection layer is appropriately formed. In another case,
the substrate is transported from the transport chamber 102 to the
film-forming chamber 106H where vapor deposition can, then, be
performed over the thus-transported substrate.
[0145] Further, in the film-forming chamber 112, the hole injection
layer comprising a polymer material may be formed by inkjetting or
spin coating. Still further, the substrate is vertically placed
and, then, film-forming is performed on the substrate under vacuum
by inkjetting. Furthermore, at least one member selected from the
group consisting of: an aqueous solution of poly(ethylene
dioxythiophene)/poly(styrene sulfonic acid) (referred to also as
PEDOT/PSS), an aqueous solution of polyaniline/camphor sulfonic
acid (referred to also as PANI/CSA), PTPDES, Et-PTPDEK, and PPBA
each of which acts as the hole injection layer (anode buffer layer)
may be applied over an entire surface of the first electrode
(anode) and baked. It is preferable that such baking is performed
in the bake chamber 123. When the hole injection layer comprising a
polymer material is formed by coating such as spin coating, a
degree of flatness is improved whereby coverage and uniformity in
thickness of a film to be formed thereon are allowed to be
favorable. Particularly, since film thickness of the light emitting
layer becomes uniform, a uniform luminescence can be obtained. In
this case, it is preferable that, after the hole injection layer is
formed by coating, vacuum heating (100.degree. C. to 200.degree.
C.) is performed on the thus-formed hole injection layer
immediately before film-forming is performed by vapor deposition.
The vacuum heating may be performed in the pretreatment chamber
103b. For example, after a surface of the first electrode (anode)
is cleaned by using a sponge, the substrate is transported into a
cassette chamber, and then, the film-forming chamber 112. After the
aqueous solution of poly(ethylene dioxythiophene)/poly(styrene
sulfonic acid) (PEDOT/PSS) is applied on an entire surface of the
first electrode (anode) with a film thickness of 60 nm, the
resultant substrate is transported in to the bake chamber 123,
pre-baked at 80.degree. C. for 10 minutes, baked in a full scale at
200.degree. C. for one hour and, thereafter, transported into the
pretreatment chamber 103b. Furthermore, after vacuum heating
(heating at 170.degree. C. for 30 minutes followed by cooling for
30 minutes) is performed immediately before vapor deposition is
performed, the resultant substrate transported sequentially into
the film-forming chambers 106R, 106G, and 106B where respective
light emitting layers may be formed by vapor deposition without
exposing the substrate to air. Particularly, in a case in which,
when an ITO film is used as a material for the anode, a surface
thereof has an uneven contour or a minute particle is present on
the surface thereof, such detrimental influences can be decreased
by allowing a film thickness of PEDOT/PSS to be 30 nm or more.
[0146] Further, when PEDOT/PSS is applied on the ITO film,
wettability thereof is not favorable; therefore, it is preferable
that, after a PEDOT/PSS solution is applied at a first time by
using spin coating, the resultant PEDOT/PSS is rinsed with pure
water, thereby enhancing the wettability thereof, and then, the
PEDOT/PSS solution is applied at a second time by using spin
coating, and thereafter, baked to form a film favorable in
uniformity. By rinsing the surface with pure water after a first
application is performed, effects not only of changing a quality of
the surface but also removing a minute particle or the like from
the surface can be exerted.
[0147] Further, when a film of PEDOT/PSS is formed by using spin
coating, the film is formed on an entire surface of the substrate.
Therefore, the film formed on each of an end portion, a peripheral
portion, a terminal portion, a connecting region between the
cathode and a lower wiring and the like is preferably removed and,
in this case, such removal is preferably performed in the
pretreatment chamber 103a by means of O.sub.2 ashing or the
like.
[0148] Next, the film-fowling chambers 106R, 106G, 106B, 106E, and
106H will be described below.
[0149] Each of the film-forming chambers 106R, 106G, 106B, 106E,
and 106H is provided with a movable vapor deposition source holder.
A plurality of such holders are prepared and appropriately provided
with a plurality of container (crucibles) which have appropriately
been filled with an EL material in a sealed manner. The substrate
is set in a face down manner, a position alignment of a vapor
deposition mask is performed by CCD or the like. Then, film-forming
can selectively be performed by executing vapor deposition by means
of a resistance heating. Further, the vapor deposition mask is
stored in a mask stock chamber 124 and it is properly transported
from there to a film-forming chamber. Still further, the
film-forming chamber 132 is a vapor deposition chamber in reserve
for forming a layer containing an organic compound or a metal
material layer.
[0150] Setting the EL material in these film-forming chambers is
preferably performed by using a manufacturing system as described
below. Namely, it is preferable that the film-forming is performed
by using the EL material which has previously been put in a
container (crucible as a typical example) by a material
manufacturer. Further, such setting is preferably executed without
exposing the EL material to air; therefore, it is preferable that,
when the container, namely, crucible, is delivered from the
material manufacturer, the crucible is put in a second container in
a sealed manner and then introduced into the film-forming chamber
as it is. Desirably, setting chambers 126R, 126G, 126B, 126E, and
126H, each of which is provided with a vacuum-evacuation device,
connected to respective film-forming chambers 106R, 106G, 106B,
106E, and 106H are allowed to be in a vacuum state or an inert gas
atmosphere, and under these circumstances the crucible is taken out
of the second container in any one of the setting chambers to set
the crucible in any one of the film-forming chambers. In such
manner, not only the crucible but also the EL material put in the
crucible are prevented from being contaminated. It is, also,
possible that the metal mask is stored in any one of the setting
chambers 126R, 126G, 126B, 126E, and 126H.
[0151] By appropriately selecting the EL material to be set in
respective film-forming chambers 106R, 106G, 106B, 106E, and 106H,
the light emitting element which emits either mono-color
(specifically white color) or full-color (specifically red, green,
and blue colors) light as a whole body of the light emitting device
can be manufactured. For example, when a green-color light emitting
element is fabricated, a hole transport layer or a hole injection
layer, a light emitting layer (G), and an electron transport layer
or an electron injection layer are laminated in this sequence in
the film-forming chamber 106H, in the film-farming chamber 106G,
and in the film-forming chamber 106E, respectively, and then, a
cathode is formed on the resultant laminar constitution to obtain
the green-color light emitting element. For example, when a
full-color light emitting element is fabricated, a hole transport
layer or a hole injection layer, a light emitting layer (R), and an
electron transport layer or an electron injection layer are
laminated in this sequence in the film-forming chamber 106R by
using a vapor deposition mask prepared exclusively for R, and then,
a hole transport layer or a hole injection layer, a light emitting
layer (G), and an electron transport layer or an electron injection
layer are laminated in this sequence over the above-formed laminar
constitution in the film-forming chamber 106G by using a vapor
deposition mask prepared exclusively for G and, thereafter, a hole
transport layer or a hole injection layer, a light emitting layer
(B), and an electron transport layer or an electron injection layer
are laminated in this sequence over the above-formed laminar
constitution in the film-forming chamber 106B by using a vapor
deposition mask prepared exclusively for B and, subsequently, a
cathode is formed over the resultant laminar constitution to obtain
the full-color light emitting element.
[0152] Further, in a case of laminating light emitting layers
having different luminescent colors from one another, an organic
compound layer which shows a white-color luminescence is roughly
classified into two types, namely, a 3 wavelength type which
contains 3 primary colors of red, green and blue and a 2 wavelength
type which utilizes a relationship of complimentary colors of
blue/yellow or bluish green/orange. It is also possible to
fabricate a white-color light emitting element in one film-forming
chamber. For example, when the white-color light emitting element
is fabricated by using the 3 wavelength type, a plurality of vapor
deposition source holders are prepared in one film-forming chamber
and therein, an aromatic diamine (TPD) is filled in a first vapor
deposition source holder in a sealed manner, p-EtTAZ is similarly
filled in a second vapor deposition source holder, Alq.sub.3 is
similarly filled in a third vapor deposition source holder, an EL
material in which Alq.sub.3 is added with Nile Red that is a red
luminescent pigment is similarly filled in a fourth vapor
deposition source holder, and Alq.sub.3 is similarly filled in a
fifth vapor deposition source holder Then, under these
configurations the first to fifth vapor deposition source holders
are set in respective film-forming chambers. Thereafter, the first
to fifth vapor deposition source holders start to move in sequence,
and then vapor deposition is performed on the substrate in a
lamination manner. Specifically, TPD is sublimated from the first
vapor deposition source holder by heating, thereby being deposited
on an entire surface of the substrate. Thereafter, p-EtTAZ is
sublimated from the second vapor deposition source holder,
Alq.sub.3 is sublimated from the third vapor deposition source
holder, Alq.sub.3:Nile Red is sublimated from the fourth vapor
deposition source holder, and Alq.sub.3 is sublimated from the
fifth vapor deposition source holder whereupon all these sublimated
materials are deposited on an entire surface of the substrate in
order. Subsequently, when a cathode is formed on the resultant
substrate, a white-color light emitting element can be
fabricated.
[0153] After the layers each containing the organic compound are
appropriately laminated in accordance with the above-described
process, the substrate is transported from the transport chamber
104a to the delivery chamber 107 and, further, from the delivery
chamber 107 to the transport chamber 108 without exposing the
substrate to air.
[0154] Next, the substrate is transported into the film-forming
chamber 110 by a transport mechanism provided in the transport
chamber 108, and then, a cathode is formed over the substrate in
the film-forming chamber 110. As for the cathode, a metal film (a
film of an alloy of, for example, MgAg, MgIn, CaF.sub.2, LiF, or
CaN, a film formed by using an element belonging to group I or II
in the periodic table and aluminum by means of co-vapor deposition,
or a laminate thereof) formed by utilizing resistance heating by
means of vapor deposition is used. Further, the cathode may also be
formed by sputtering.
[0155] When a top emission type light emitting device is
manufactured, it is preferable that a cathode is transparent or
translucent. It is also preferable that a thin film (1 nm to 10 nm)
of the above-described metal film, or a laminate of the thin film
(1 nm to 10 nm) of the above-described metal film and an conductive
transparent film is allowed to be the cathode. In this case, a film
comprising the transparent conductive film (for example, indium
oxide-tin oxide alloy (ITO), indium oxide-zinc oxide alloy
(In.sub.2O.sub.3--ZnO), or zinc oxide (ZnO)) may be formed in the
film-forming chamber 109 by using sputtering.
[0156] A light emitting device having a laminar constitution is
manufactured by the process described above.
[0157] Further, the substrate is transported into the film-forming
chamber 113 connected to the transport chamber 108, and then, in
the film-forming chamber 113, a protective film comprising a
silicon nitride film or a silicon oxynitride film may be formed to
seal it. In the present embodiment, a target comprising silicon or
a target comprising silicon oxide, or a target comprising silicon
nitride is provided in the film-forming chamber 113. For example, a
silicon nitride film can be formed over the cathode by using a
target comprising silicon and by allowing the inside of the
film-forming chamber to be in a nitrogen gas atmosphere or an
atmosphere containing nitrogen and argon gases. Further, a thin
film (for example, DLC film, CN film, or amorphous carbon film)
containing carbon as a primary component may be rimmed as a
protective film, and separately, a film-forming chamber using
chemical vapor deposition (CVD) may be provided. A diamond-like
carbon film (referred to also as DLC film) can be formed by at
least one method selected from the group consisting of: plasma CVD
(as a typical example, RF plasma CVD, microwave CVD, electron
cyclotron resonance (ECR) CVD, or hot-filament CVD),
combustion-flame, sputtering, ion beam vapor deposition, and laser
vapor deposition. As for reaction gases to be used in film-forming,
a hydrogen gas, and at least one of hydrocarbon-type gases (for
example, CH.sub.4, C.sub.2H.sub.2, and C.sub.6H.sub.6) are used.
These gases are ionized by glow discharge, and after being
accelerated in velocity, the resultant ions collides with a cathode
which is applied with negative self-bias, thereby forming a film.
Further, the CN film may be formed by using C.sub.2H.sub.4 gas and
N.sub.2 gas as reaction gas. Still further, the DLC film or the CN
film is a transparent or translucent insulating film against
visible light. The term "transparent against visible light" used
herein is intended to mean that a transmission factor of the
visible light is in the range of from 80% to 100% while the term
"translucent against visible light" used herein is intended to mean
that a transmission factor of the visible light is in the range of
from 50% to 80%.
[0158] In the present embodiment, a protective film comprising a
laminate comprising a first inorganic insulating film, a stress
relaxing film, and a second inorganic insulating film is formed
over a cathode. For example, it is permissible that, after the
cathode is formed, the substrate is transported into the
film-forming chamber 113 where the first inorganic insulating film
is formed and, then, the resultant substrate is transported into
the film-forming chamber 132 where the stress relaxation layer (for
example, a layer containing an organic compound) having a
hygroscopic property and transparency is formed thereon and,
thereafter, the resultant substrate is transported back to the
film-forming chamber 113 where the second inorganic insulating film
is formed thereon.
[0159] Next, the substrate over which a light emitting element is
thus formed is transported from the transport chamber 108 to the
delivery chamber 111 without exposing the substrate to air, and
then, from the delivery chamber 111 to the transport chamber 114.
Subsequently, the substrate over which the light emitting element
is formed is transported from the transport chamber 114 to the
sealing chamber 116.
[0160] A sealed substrate is set in a load chamber 117 from outside
and ready to be processed. Further, it is preferable that, in order
to remove impurities such as moisture, the substrate has previously
been subjected to annealing under vacuum. When a sealing material
is formed for bonding the sealed substrate with the substrate over
which the light emitting element is formed, the sealing material is
formed in the sealing chamber and the sealed substrate over which
the sealing material was formed is transported into the sealed
substrate stock chamber 130. Further, a desiccant may be attached
to the sealed substrate in the sealing chamber. Still further, in
the present embodiment, an example in which the sealing material is
formed over the sealed substrate is described; however, the present
invention is by no means limited to the example and the sealing
material may be formed over the substrate over which the light
emitting element has previously been formed.
[0161] Next, the substrate and the sealed substrate are bonded to
each other in the sealing chamber 116, and then, the thus-bonded
pair of substrates is irradiated with ultraviolet light by using an
ultraviolet ray irradiation mechanism provided in the sealing
chamber 116 to cure the sealing material. Further, in the present
embodiment, an ultraviolet ray-curing type resin is used as the
sealing material; however, no particular limitation is put on the
sealing material so long as it is an adhesive.
[0162] Subsequently, the thus-bonded pair of substrates are
transported from the sealing chamber 116 to the transport chamber
114, and then, from the transport chamber 114 to the extraction
chamber 119 where the resultant substrate is taken out.
[0163] As described above, since the light emitting element is not
exposed to air at all until it is sealed in a sealed space by using
the manufacturing apparatus as shown in FIG. 6, a light emitting
device having high reliability can be manufactured. Further,
although a vacuum state and a nitrogen atmosphere under an
atmospheric pressure are alternately repeated in the transport
chambers 114 and 118, it is preferable that the transport chambers
102, 104a, and 108 are consistently maintained in a vacuum
state.
[0164] Although not shown, a control device, which realizes
automation by controlling a pathway along which the substrate is
moved into each treatment chamber, is provided.
[0165] Further, in the manufacturing apparatus as shown in FIG. 6,
it is also possible that a substrate, over which a transparent
conductive film (or metal film (TiN)) is provided as an anode is
transported in, and after a layer containing an organic compound is
formed over the substrate, a transparent or translucent cathode
(for example, a laminate of a thin metal film (for example, Al, or
Ag) and a transparent conductive film) is formed over the resultant
substrate to fabricate an top emission type (or top-bottom emission
type) light emitting element. The term "top emission type light
emitting element" used herein is intended to mean an element which
takes out luminescence that is generated in the organic compound
layer by allowing it to pass through the cathode.
[0166] Further, in the manufacturing apparatus as shown in FIG. 6,
it is also possible that a substrate, over which a transparent
conductive film is provided as an anode, is transported in, and,
after a layer containing an organic compound is formed over the
substrate, a cathode comprising a metal film (for example, Al, or
Ag) is formed over the substrate to fabricate a bottom emission
type light emitting element. The term "bottom emission type light
emitting element" used herein is intended to mean an element which
takes out luminescence that is generated in the organic compound
layer from a transparent electrode, namely, an anode, in the
direction of TFT, and further, allows the luminescence to pass
through the substrate.
[0167] Further, the present embodiment can freely be combined with
any one of Embodiment Modes 1 to 3 and Example 1.
Embodiment 3
[0168] An example of obtaining a full-color light emitting element
by selectively forming layers containing respective organic
compounds, which can obtain R, G, and B luminescence by using a
manufacturing apparatus as described in Embodiment 2, will be
described below.
[0169] In the present embodiment, an example, in which a light
emitting area of each of a red-color light emitting element, a
green-color light emitting element, and a blue-color light emitting
element which are different in light emitting efficiency from one
another is allowed to be changed, will be described. Further, it is
preferable that film thickness of a hole transport layer or a hole
injection layer, or an electron transport layer or an electron
injection layer is appropriately changed in order to correspond to
each luminescent color. In the present embodiment, an example in
which a red-color light emitting area is larger than a blue-color
light emitting area which is larger than a green-color light
emitting area is described and should not be interpreted as
limiting the present invention in any way.
[0170] FIG. 7A shows a view of a vapor deposition mask for R; FIG.
7B shows a view of a vapor deposition mask for B; and FIG. 7C shows
a view of a vapor deposition mask for G.
[0171] When a hole transport layer or a hole injection layer, a
light emitting layer (R), and an electron transport layer or an
electron injection layer are laminated in this sequence in the
film-forming chamber 106R by using a vapor deposition mask (see
FIG. 7A) prepared for R and, then, a hole transport layer or a hole
injection layer, a light emitting layer (G), and an electron
transport layer or an electron injection layer are laminated in
this sequence in the film-forming chamber 106G by using a vapor
deposition mask (see FIG. 7C) prepared for G and, thereafter, a
hole transport layer or a hole injection layer, a light emitting
layer (B), and an electron transport layer or an electron injection
layer are laminated in this sequence in the film-forming chamber
106B by using a vapor deposition mask (see FIG. 7B) prepared for B
and, subsequently. A cathode is subsequently formed over the
resultant laminate, and then, a full-color light emitting element
can be fabricated. A part of the thus-fabricated light emitting
region (light emitting region corresponding to 8 pixels) is shown
in FIG. 7D.
[0172] Further, the present embodiment can freely be combined with
any one of Embodiment Modes 1 to 3, and Examples 1 and 2.
Embodiment 4
[0173] In the present embodiment, an example of an element which
not only enhances mobility of a carrier by relaxing an energy
barrier that is present in an organic compound film, but also
performs function separation of a laminar constitution while
holding respective functions of plurality of various types of
materials as well, is described.
[0174] In regard to relaxation of the energy barrier in the laminar
constitution, a technique of inserting a carrier injection layer is
well referred to. That is, by inserting a material which relaxes
the energy barrier present in an interface of the laminar
constitution having a large energy barrier into the interface, a
design can be made such that the energy barrier is set in a
stepwise pattern. By making such design, a property of a carrier
injection from the electrode can be enhanced to surely reduce a
drive voltage to certain extent. However, there is a problem in
that, by increasing a number of layers, a number of organic
interfaces are increased as well. It is considered that such
feature is the reason why a monolayer constitution rather holds top
data of drive voltage/power efficiency. In other words, by
overcoming the problem, the laminar constitution can reach the
drive voltage/power efficiency of the monolayer constitution, while
maintaining a merit (capability of combinations of various types of
materials free from necessity of a complicated design of molecules)
of the laminar constitution.
[0175] Under these circumstances, in the present embodiment, when
an organic compound film comprising a plurality of functional
regions is formed between a cathode and an anode of a light
emitting element, a constitution having a mixed region, which is
different from a conventional laminar constitution in which a
distinct interface is present, comprising simultaneously a material
which constitutes a first functional region and another material
which constitutes a second functional region is formed between the
first functional region and the second functional region.
[0176] The present embodiment also includes the case where a
material that is capable of converting triplet excitation energy
into light emission is added to the mixed region as a dorpant. In
addition in the formation of the mixed region, the mixed region may
be funned to have a connection gradient.
[0177] It is considered that, by applying such constitution as
described above, the energy barrier which is present between
functional regions is reduced compared with the conventional
constitution, thereby improving the carrier injection property.
That is, the energy barrier between functional regions is relaxed
by forming the mixed region and, accordingly, prevention of
reduction for drive voltage and luminance can be realized.
[0178] Therefore, in the present embodiment, when a light emitting
element comprising at least a region (referred to as a first
functional region) in which a first organic compound can exhibit a
function thereof and another region (referred to as a second
functional region) in which a second organic compound, being
different from a substance which constitutes the first functional
region, can exhibit a function thereof, and a light emitting device
comprising such light emitting element are manufactured, a mixed
region, containing the organic compound which constitutes the first
functional region and another organic compound which constitutes
the second functional region, is prepared between the first
functional region and the second functional region.
[0179] A film-forming apparatus is configured such that an organic
compound film having a plurality of functional regions can be
formed in one film-forming chamber, and a plurality of vapor
deposition sources are provided in correspondence with such
plurality of functional regions.
[0180] Firstly, a first organic compound is vapor deposited. The
first organic compound, which has previously been vaporized by
resistance heating, is scattered in the direction of the substrate
by opening a shutter at the time of vapor deposition, and
accordingly, a first functional region 610 as shown in FIG. 8A can
be formed.
[0181] Next, while keeping a state in which the first organic
compound is vapor deposited, a first shutter is opened, and then, a
second organic compound is vapor deposited. Further, the second
organic compound which has also previously been vaporized by
resistance heating is scattered in the direction of the substrate
by opening a second shutter at the time of vapor deposition.
Accordingly, a first mixed region 611 comprising the first organic
compound and the second organic compound can be formed.
[0182] Then, after a while, only the first shutter is closed to
allow the second organic compound to be vapor deposited.
Accordingly, a second functional region 612 can be formed.
[0183] Further, in the present embodiment, a case in which the
mixed region is formed by allowing two types of organic compounds
to be simultaneously vapor deposited is described. However, it is
also possible that the first organic compound is first vapor
deposited, and then, a mixed region is formed between the first
functional region and the second functional region by allowing the
second organic compound to be vapor deposited in an atmosphere of
such vapor deposition of the first organic compound.
[0184] Subsequently, while keeping a state in which the second
organic compound is vapor deposited, a third shutter is opened, and
then, a third organic compound is vapor deposited. Further, the
third organic compound, which has also previously been vaporized by
resistance heating, is scattered in the direction of the substrate
by opening the shutter at the time of vapor deposition.
Accordingly, a second mixed region 613 comprising the second
organic compound and the third organic compound can be formed.
[0185] Then, after a while, only the second shutter is closed to
allow the third organic compound to be vapor deposited.
Accordingly, a third functional region 614 can be formed.
[0186] Finally, a light emitting element is completed by forming a
cathode over the resultant substrate.
[0187] Further, as for another organic compound films as shown in
FIG. 8B, after a first functional region 620 is formed by using the
first organic compound, a first mixed region 621 comprising the
first organic compound and the second organic compound is formed,
and then, a second functional region 622 is formed by using the
second organic compound. Thereafter, in a midway in which the
second functional region 622 is formed, the third shutter is
temporarily opened to allow a third organic compound to be
simultaneously vapor deposited, and then the second mixed region
623 is formed.
[0188] Then, after a while, the second functional region 622 is
formed again by closing the third shutter. Thereafter, a cathode is
formed over the resultant substrate, thereby fabricating a light
emitting element.
[0189] Since an organic compound film having a plurality of
functional regions can be formed in one film-forming chamber, a
functional region interface is not contaminated by impurities, and
also, a mixed region can be formed in a functional region
interface. Under these circumstances, a light emitting element
having no distinct laminar constitution (namely, free from a
distinct organic interface) but having a plurality of functions can
be fabricated.
[0190] Further, when the film-forming unit which can perform vacuum
annealing before, during, or after a film-forming operation is
executed is employed, a more fitting intermolecular state in the
mixed region can be established by performing vacuum annealing
during the film-forming operation is executed. Accordingly, it
becomes possible to prevent the drive voltage and luminance from
being reduced. Further, impurities, such as oxygen and moisture
containing in the organic compound layer that has been formed over
the substrate are further removed by performing such annealing
(evacuation) operation after the film is formed. Thus, the organic
compound layer having high density and high purity can be
formed.
[0191] Further, the present embodiment can be freely combined with
any one of Embodiment Modes 1 to 3 and Embodiment 1 to 3.
Embodiment 5
[0192] Various modules (active matrix type liquid crystal module,
active matrix type EL module and active matrix type EC module) can
be completed by implementing the present invention. Thus, all of
the electronic apparatuses incorporated these modules into display
portions can be completed.
[0193] Following can be given as such electronic apparatuses: video
cameras; digital cameras; head mounted displays (goggle type
displays); car navigation systems; projectors; car stereos;
personal computers; portable information terminals (mobile
computers, mobile phones or electronic books etc.) etc. Practical
examples thereof are shown in FIGS. 9A to 9E and FIGS. 10A to
10C.
[0194] FIG. 9A is a personal computer which comprises: a main body
2001; an image input portion 2002; a display portion 2003; and a
keyboard 2004 etc.
[0195] FIG. 9B is a video camera which comprises: a main body 2101;
a display portion 2102; a voice input portion 2103; operation
switches 2104; a battery 2105 and an image receiving portion 2106
etc.
[0196] FIG. 9C is a mobile computer which comprises: a main body
2201; a camera portion 2202; an image receiving portion 2203;
operation switches 2204 and a display portion 2205 etc.
[0197] FIG. 9D is a player using a recording medium recording a
program (hereinafter, recording medium) which comprises: a main
body 2401; a display portion 2402; a speaker portion 2403; a
recording medium 2404 and an operation switch 2405 etc. Note that a
DVD (Digital Versatile Disc), a CD or the like is used as a
recording medium for this player, and that application of listening
music, viewing movie, game or the Internet can be done.
[0198] FIG. 9E is a digital camera which comprises: a main body
2501; a display portion 2502; a view finder 2503; operation
switches 2504; and an image receiving portion (not shown in the
figure) etc.
[0199] FIG. 10A is a mobile phone which comprises: a main body
2901; a voice output portion 2902; a voice input portion 2903; a
display portion 2904; operation switches 2905; an antenna 2906; and
an image input portion (CCD, image sensor, etc.) 2907 etc.
[0200] FIG. 10B is a portable book (electronic book) which
comprises: a main body 3001; display portions 3002 and 3003; a
recording medium 3004; operation switches 3005 and an antenna 3006
etc.
[0201] FIG. 10C is a display which comprises: a main body 3101; a
supporting portion 3102; and a display portion 3103 etc.
[0202] In addition, the display shown in FIG. 10C has a screen in
small, medium or large size, for example a size of 5 to 20 inches.
Further, to manufacture the display part with such sizes, it is
preferable to mass-produce by taking multiple pattern using a
substrate with one meter on a side.
[0203] As described above, the applicable range of the present
invention is so wide that the invention can be applied to
electronic apparatuses of various fields. Note that the electronic
apparatuses of this embodiment can be achieved by utilizing any
combination of constitutions in Embodiment Mode 1 to 3 and
Embodiment 1 to 4.
Embodiment 6
[0204] The electronic apparatuses represented in Embodiment Mode 5
includes a panel in which a light emitting element is sealed,
loaded a module provided with a controller and an IC including a
circuit such as a power source circuit. The module and the panel
are both corresponding to one mode of the light emitting device. In
the present invention, a specific configuration of the module will
be described.
[0205] FIG. 11A shows an appearance of a module in which a panel
800 is provided with a controller 801 and a power source circuit
802. There are provided in the panel 800 with a pixel portion 803
in which a light emitting element is provided in each pixel, a gate
line driving circuit 804 for selecting a pixel in the pixel portion
803, and a source line driving circuit 805 for supplying a video
signal to the selected pixel.
[0206] The controller 801 and the power source circuit 802 are
provided in a printed substrate 806. Various signals or power
source voltage, which are output from the controller 801 or the
power source circuit 802 respectively, are supplied through FPC 807
to the pixel portion 803, the gate line driving circuit 804, and
the source line driving circuit 805 on the panel 800.
[0207] Through an interface (I/F) 808 in which a plurality of input
terminals are arranged, power source voltage and various signals to
the printed circuit 806 is supplied.
[0208] Although the printed substrate 806 is attached to the panel
800 with FPC in the present embodiment, the present invention is
not limited to this configuration. The controller 801 and the power
source circuit 802 may be provided directly in the panel 800 with
COG (Chip on Glass) manner.
[0209] Further, as for the printed circuit 806, there is a case
that a capacity formed between leading wirings and a resistance of
a wiring itself cause a noise to a power source voltage or a
signal, or make a rise of a signal dull. Therefore, it may be
prevent the noise to the power source voltage or a signal and the
dull rise of the signal to provide various kinds of elements such
as a capacitor and a buffer in the printed substrate 806.
[0210] FIG. 11B is a block diagram showing a configuration of the
printed substrate 806. Various kinds of signals and power source
voltage supplied to the interface 808 are supplied to the
controller 801 and the power source circuit 802.
[0211] The controller 801 has an A/D converter 809, a phase locked
loop (PLL) 810, control signal generating portion 811, and SRAM
(Static Random Access Memory) 812 and 813. Although the SRAM is
used in the present embodiment, instead of the SRAM, SDRAM can be
used and DRAM (Dynamic Random Access Memory) can also be used if it
is possible to write in and read out data at high speed.
[0212] Video signals supplied via the interface 808 are subjected
to a parallel-serial conversion in the A/D converter 809 to be
input into the control signal generating portion 811 as video
signals corresponding to respective colors of R, G, and B. Further,
based on various kinds of signals supplied via the interface 808,
Hsync signal, Vsync signal, clock signal CLK, and a volts
alternating current (AC cont) are generated in the A/D converter
809 to be input into the control signal generating portion 811.
[0213] The phase locked loop 810 has a function of synchronizing
frequencies of the various kinds of signals supplied via the
interface 808 and an operation frequency of the control signal
generating portion 811. The operation frequency of the control
signal generating portion 811 is not always the same as the
frequencies of the various kinds of signals supplied via the
interface 808, however, the frequency of the control signal
generating portion 811 is controlled in the phase locked loop 810
in order to synchronize each other.
[0214] The video signals input to the control signal generating
portion 811 are once written in SRAM 812 and 813 and stored. In the
control signal generating portion 811, video signals stored in the
SRAM 812 which is corresponding to all pixels are read out per one
bit, and input to a signal line driving circuit 805 of the panel
800.
[0215] Further, in the control signal generating portion 811,
information for each bit regarding a period during which the light
emitting element emits light, is input to a scanning line driving
circuit 804 of the panel 800.
[0216] In addition, the power source circuit 802 supplies a
predetermined supply voltage to the signal line driving circuit
805, the scanning line driving circuit 804 and the pixel portion
803 of the panel 800.
[0217] Next, a detailed configuration of the power source circuit
802 will be described with FIG. 12. The power source circuit 802 of
the present embodiment is composed of a switching regulator 854
that employs four switching regulator controls 860 and a series
regulator 855.
[0218] In general, a switching regulator is smaller and lighter
than a series regulator, and capable of not only step-down but also
step-up, and inversion of positive and negative. On the other hand,
the seried regulator is used only for step-down while an output
voltage has a high precision, compared to the switching regulator,
and there are almost no possibility for occurrence of a ripple or a
noise. The power source circuit 802 in the present embodiment uses
the both combined.
[0219] The switching regulator 854 shown in FIG. 12 has the
switching regulator controls (SWR) 860, attenuators (ATT) 861,
transformers (T) 862, inductors (L) 863, a reference power source
(Vref) 864, an oscillation circuit (OSC) 865, diodes 866, bipolar
transistor 867, a variable resistor 868, and a capacity 869.
[0220] When a voltage of such an outside Li ion buttery (3.6V) is
converted in the switching regulator 854, a power source voltage
given to a cathode and a power source voltage supplied to a
switching regulator 854 are generated.
[0221] Further, a series regulator 855 has a band gap circuit (BG)
870, an amplifier 871, operation amplifiers 872, a current source
873, variable resistors 874 and bipolar transistors 875, and a
power source voltage generated in a switching regulator 854 is
supplied thereto.
[0222] In a series regulator 855, based on a predetermined
electronic voltage generated in the band gap circuit 870, a power
source voltage of a direct current is generated, which is to be
given a wiring (referred to also as a wiring for the current
supply) for supplying a current to an anode of a light emitting
element corresponding to each color using a direct current of power
source voltage generated in switching regulator 854.
[0223] Still, a current source 873 is used in the case of the
driving method that the electric current of video signal is written
in the pixel. In this case, the electric current generated in
current source 873 is provided for a signal line driving circuit
805. However, a current source 873 is not indispensable in the case
the driving method that voltage of a video signal is written in the
pixel.
[0224] It is possible to form a switching regulator, an OSC, an
amplifier and an operation amplifier using TFT.
[0225] The present embodiment may be freely combined with any of
the structures of Embodiment Mode 1 to 3 and Embodiment 1 to 5.
Embodiment 7
[0226] Also, a stress relaxing film can be provided between a metal
layer and a inorganic insulating film. An example thereof is shown
in FIGS. 13A and 13B.
[0227] Since the example shown in FIG. 13A is constituted in a same
manner as in FIG. 1A except for a part (a transparent protective
laminate), same reference numerals are applied to parts identical
to those in FIG. 1A.
[0228] Reference numeral 1312 denotes a transparent protective
laminate to be formed by sputtering or vapor deposition and the
layer becomes a sealing film which not only protects the second
electrode 311 comprising a metal thin film but also prevents
penetration of moisture. As shown in FIG. 13A, the transparent
protective laminate 1312 comprises a laminate comprising a stress
relaxing film 1312a, an inorganic insulating film 1312b, a stress
relaxing film 1312c, and an inorganic insulating film 1312d.
[0229] The structure shown in FIG. 13A is effective when the
difference between the film stress of a second electrode 311 and
the film stress of an inorganic insulating film 1312b is wide.
Further, stress can be relaxed and, also, moisture can be absorbed
by sandwiching the stress relaxing film 1312a between the second
electrode 311 and the inorganic insulating film 1312b.
[0230] As for materials for the stress relaxing film 1312a and
1312c, a material which has smaller stress than the inorganic
insulating films 1312b and 1312d and has a hygroscopic property is
preferable. In addition to the above-described properties material
having a translucent property is desirable. As for the stress
relaxing film 1312a and 1312c, a material film containing an
organic compound such as .alpha.-NPD
(4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl), BCP
(bathocuproin), MTDATA
(4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino) triphenylamine),
and Alq.sub.3 (a tris-8-quinolinolate aluminum complex) may be
used. These material films each have a hygroscopic property. When
they become thin in thickness, they become nearly transparent.
Since MgO, SrO.sub.2, and SrO each have a hygroscopic property and
translucent property and a thin film thereof can be obtained by
vapor deposition, any one of these oxides can be used as the stress
relaxing film 1312a and 1312c.
[0231] As for the stress relaxing film 1312a and 1312c, the same
material used in a layer, containing an organic compound, which is
sandwiched between the cathode and the anode can also be used.
[0232] The present embodiment can be freely combined with
Embodiment Mode 1.
[0233] Also, the other example is shown in FIG. 13B. Since the
example shown in FIG. 13B is constituted in a same manner as in
FIG. 3B except for a transparent protective laminate, same
reference numerals are applied to parts identical to those in FIG.
3B.
[0234] Reference numeral 1512 denotes a protective laminate to be
formed by sputtering or vapor deposition and the layer becomes a
sealing film which not only protects the second electrode 511
comprising a metal thin film but also prevents penetration of
moisture. As shown in FIG. 13B, the transparent protective laminate
1512 comprises a laminate comprising a stress relaxing film 1512a,
an inorganic insulating film 1512b, a stress relaxing film 1512c,
and an inorganic insulating film 1512d.
[0235] Since Embodiment Mode 7 is a bottom emission type, the
protective laminate 1512 is not necessarily transparent and film
thickness can be thick.
[0236] The structure shown in FIG. 13B is effective when the
difference between the film stress of a second electrode 511 and
the film stress of an inorganic insulating film 1512b is wide.
Further, stress can be relaxed and, also, moisture can be absorbed
by sandwiching the stress relaxing film 1512a between the second
electrode 511 and the inorganic insulating film 1512b.
[0237] As for materials for the stress relaxing film 1512a and
1512c, a material which has smaller stress than the inorganic
insulating films 1312b and 1312d and has a hygroscopic property is
preferable. As for the stress relaxing film 1512a and 1512c, a
material film containing an organic compound such as .alpha.-NPD
(4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl), BCP
(bathocuproin), MTDATA
(4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino) triphenylamine, and
Alq.sub.3 (a tris-8-quinolinolate aluminum complex) may be used.
Since MgO, SrO.sub.2, and SrO each have a hygroscopic property and
a thin film thereof can be obtained by vapor deposition, any one of
these oxides can be used as the stress relaxing film 1512a and
1512c.
[0238] As for the stress relaxing film 1512a and 1512c, the same
material used in a layer containing an organic compound, which is
sandwiched between the cathode and the anode can also be used.
[0239] Further, the present embodiment can freely be combined with
any one of Embodiment Modes 1 to 3, and Embodiments 1 to 6.
[0240] According to the present invention, a protective layer
having high blocking effect against oxygen and moisture can be
provided and a light emitting device having a high-reliability can
be realized.
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