U.S. patent application number 15/042698 was filed with the patent office on 2016-08-25 for display device and method for fabricating the same.
This patent application is currently assigned to Semiconductor Energy Laboratory Co., Ltd.. The applicant listed for this patent is Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Jun Koyama.
Application Number | 20160248044 15/042698 |
Document ID | / |
Family ID | 26586478 |
Filed Date | 2016-08-25 |
United States Patent
Application |
20160248044 |
Kind Code |
A1 |
Koyama; Jun |
August 25, 2016 |
Display Device and Method for Fabricating the Same
Abstract
An inexpensive display device, as well as an electrical
apparatus employing the same, can be provided. In the display
device in which a pixel section and a driver circuit are included
on one and the same insulating surface, the driver circuit includes
a decoder 100 and a buffer section 101. The decoder 100 includes a
plurality of NAND circuits each including p-channel TFTs 104 to 106
connected to each other in parallel and other p-channel TFTs 107 to
109 connected to each other in series. The buffer section 101
includes a plurality of buffers each including three p-channel TFTs
114 to 116.
Inventors: |
Koyama; Jun; (Kanagawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Kanagawa-ken |
|
JP |
|
|
Assignee: |
Semiconductor Energy Laboratory
Co., Ltd.
Kanagawa-ken
JP
|
Family ID: |
26586478 |
Appl. No.: |
15/042698 |
Filed: |
February 12, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14263396 |
Apr 28, 2014 |
9263476 |
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15042698 |
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13731482 |
Dec 31, 2012 |
8717262 |
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14263396 |
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12609924 |
Oct 30, 2009 |
8344992 |
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13731482 |
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09791182 |
Feb 23, 2001 |
7612753 |
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12609924 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/3276 20130101;
H01L 51/524 20130101; G09G 3/3291 20130101; G09G 2310/027 20130101;
G09G 3/3648 20130101; G09G 2300/0842 20130101; H01L 27/3211
20130101; G02F 1/136286 20130101; H01L 51/5253 20130101; G09G
3/3266 20130101; G09G 2300/0861 20130101; H01L 27/1248 20130101;
H01L 51/0097 20130101; H01L 2924/0002 20130101; H01L 27/3248
20130101; H01L 2924/0002 20130101; H01L 2251/5338 20130101; H01L
2251/301 20130101; H01L 27/1222 20130101; H01L 2924/00 20130101;
G09G 3/3233 20130101; H01L 27/3279 20130101; H01L 27/124
20130101 |
International
Class: |
H01L 51/52 20060101
H01L051/52; H01L 27/32 20060101 H01L027/32; H01L 51/00 20060101
H01L051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 29, 2000 |
JP |
2000-055013 |
Feb 29, 2000 |
JP |
2000-055017 |
Claims
1. (canceled)
2. A light-emitting device comprising: a plastic substrate; a first
adhesive over the plastic substrate; an insulating film comprising
silicon and nitrogen; a cathode of an EL element over the
insulating film; and a second adhesive over the cathode of the EL
element.
3. The light-emitting device according to claim 2, further
comprising a pixel, wherein the pixel comprises a first transistor
and a second transistor and the EL element, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is electrically connected to a current supply
line, wherein one of a source and a drain of the second transistor
is electrically connected to a gate of the first transistor,
wherein a gate of the second transistor is electrically connected
to a gate wiring, and wherein the current supply line is parallel
to the gate wiring.
4. The light-emitting device according to claim 3, wherein the
other of the source and the drain of the second transistor is
electrically connected to a source wiring.
5. The light-emitting device according to claim 2, further
comprising a first pixel and a second pixel, wherein the first
pixel comprises a first transistor and the EL element, wherein the
second pixel comprises a second transistor, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is directly connected to a current supply
line, and wherein one of a source and a drain of the second
transistor is directly connected to the current supply line.
6. The light-emitting device according to claim 2, further
comprising a pixel, wherein the pixel comprises a first transistor
and a second transistor and the EL element, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is electrically connected to one of a source
and a drain of the second transistor, and wherein the other of the
source and the drain of the second transistor is electrically
connected to a current supply line.
7. The light-emitting device according to claim 6, wherein the
other of the source and the drain of the second transistor is
directly connected to the current supply line.
8. A light-emitting device comprising: a plastic substrate; a first
adhesive over the plastic substrate; an insulating film comprising
silicon and nitrogen; a cathode of an EL element over the
insulating film; a second adhesive over the cathode of the EL
element; and a cover member over the second adhesive.
9. The light-emitting device according to claim 8, further
comprising a pixel, wherein the pixel comprises a first transistor
and a second transistor and the EL element, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is electrically connected to a current supply
line, wherein one of a source and a drain of the second transistor
is electrically connected to a gate of the first transistor,
wherein a gate of the second transistor is electrically connected
to a gate wiring, and wherein the current supply line is parallel
to the gate wiring.
10. The light-emitting device according to claim 9, wherein the
other of the source and the drain of the second transistor is
electrically connected to a source wiring.
11. The light-emitting device according to claim 8, further
comprising a first pixel and a second pixel, wherein the first
pixel comprises a first transistor and the EL element, wherein the
second pixel comprises a second transistor, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is directly connected to a current supply
line, and wherein one of a source and a drain of the second
transistor is directly connected to the current supply line.
12. The light-emitting device according to claim 8, further
comprising a pixel, wherein the pixel comprises a first transistor
and a second transistor and the EL element, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is electrically connected to one of a source
and a drain of the second transistor, and wherein the other of the
source and the drain of the second transistor is electrically
connected to a current supply line.
13. The light-emitting device according to claim 12, wherein the
other of the source and the drain of the second transistor is
directly connected to the current supply line.
14. A light-emitting device comprising: a substrate; a first
adhesive over the substrate; an insulating film comprising silicon
and nitrogen; a cathode of an EL element over the insulating film;
a second adhesive over the cathode of the EL element; and a cover
member over the second adhesive, wherein each of the substrate and
the cover member is a PET film.
15. The light-emitting device according to claim 14, further
comprising a pixel, wherein the pixel comprises a first transistor
and a second transistor and the EL element, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is electrically connected to a current supply
line, wherein one of a source and a drain of the second transistor
is electrically connected to a gate of the first transistor,
wherein a gate of the second transistor is electrically connected
to a gate wiring, and wherein the current supply line is parallel
to the gate wiring.
16. The light-emitting device according to claim 15, wherein the
other of the source and the drain of the second transistor is
electrically connected to a source wiring.
17. The light-emitting device according to claim 14, further
comprising a first pixel and a second pixel, wherein the first
pixel comprises a first transistor and the EL element, wherein the
second pixel comprises a second transistor, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is directly connected to a current supply
line, and wherein one of a source and a drain of the second
transistor is directly connected to the current supply line.
18. The light-emitting device according to claim 14, further
comprising a pixel, wherein the pixel comprises a first transistor
and a second transistor and the EL element, wherein one of a source
and a drain of the first transistor is electrically connected to
the EL element, wherein the other of the source and the drain of
the first transistor is electrically connected to one of a source
and a drain of the second transistor, and wherein the other of the
source and the drain of the second transistor is electrically
connected to a current supply line.
19. The light-emitting device according to claim 18, wherein the
other of the source and the drain of the second transistor is
directly connected to the current supply line.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a device having an element
in which a light-emitting material is interposed between electrodes
(hereinafter, such a device is referred to as the light-emitting
device and such an element is referred to as the light-emitting
element). In particular, the present invention relates to a device
including on one and the same insulating surface, a pixel section
and a driver circuit for transmitting a signal to the pixel
section. In addition, the present invention can be used for a
device having an element in which liquid crystal is interposed
between electrodes (hereinafter, such a device is referred to as
the liquid crystal display device and such an element is referred
to as the liquid crystal element). It should be noted that in the
present specification, the light-emitting device and the liquid
crystal display device are collectively referred to as the display
device.
[0003] Light-emitting materials that can be used in the present
invention include all of light-emitting materials that emit light
(phosphorescent light and/or fluorescent light) via singlet
excitation or triplet excitation, or both of these excitations.
[0004] 2. Description of the Related Art
[0005] Recently, developments for a light-emitting device including
a light-emitting element which utilizes a light-emitting material
capable of providing EL (Electro Luminescence) has been progressed
(hereinafter, such a light-emitting device is simply referred to as
the light-emitting device; such a light-emitting element is
referred to as the EL element; and such a light-emitting material
is referred to as the EL material). The light-emitting device has a
structure having an EL element in which a thin film made of the EL
material is interposed between an anode and a cathode.
[0006] Although in the developments for the light-emitting devices
the passive-matrix type devices have been mainly focused. it has
been considered that there will exist disadvantages with the
passive-matrix type light-emitting devices in that a sufficient
reliability (a long lifetime of the EL element) cannot be ensured
with a higher precision pixel section which requires the luminance
of the EL element to be increased. From the above circumstances,
the active-matrix type light-emitting devices are recently drawing
much attention for the purpose of realizing a higher precision
display. The active-matrix type light-emitting device is
characterized in that an active element is provided within each
pixel so that the EL element is allowed to emit light in accordance
with an input signal. As the active element, a TFT (Thin Film
Transistor) is commonly employed.
[0007] Reference is now made to FIG. 4, which illustrates a pixel
structure of the active-matrix type light-emitting device. In FIG.
4, reference numeral 401 denotes a source wiring, 402 denotes a
gate wiring, 403 denotes a TFT functioning as a switching element
(hereinafter referred to as the switching TFT), and 404 denotes a
capacitor electrically connected to a drain of the switching TFT
403.
[0008] The drain of the switching TFT 403 is also electrically
connected to a gate electrode of a current-controlling TFT 405. A
source of the current-controlling TFT 405 is electrically connected
to a current supply line 406, while a drain thereof is electrically
connected to an EL element 407. In other word, the
current-controlling TFT 405 can function as an element for
controlling current flowing through the EL element 407.
[0009] The luminance of the EL element can be controlled by thus
providing the two TFTs having different functions, respectively, in
each of the pixels. As a result, a light-emitting period can
substantially correspond to one-frame period, and an image can be
displayed while suppressing the luminance even with a higher
precision pixel section. Furthermore, advantages of the
active-matrix type device include the capability of forming, as a
driver circuit for transmitting a signal to the pixel section, a
shift register or a sampling circuit with TFTs on the same
substrate. This enables fabrication of a very compact
light-emitting device.
[0010] However, it is difficult to ensure a sufficient production
yield of the active-matrix type light-emitting device, as compared
to the passive-matrix type device that has a simpler structure,
since a plurality of TFTs have to be formed on the same substrate
in the active-matrix type device. Particularly in the case where
the driver circuit is to he provided on the same substrate, a line
defect may arise in which one line of the pixels does not operate
because of a defect of operation. In addition, since fabrication
steps for the TFTs are relatively complicated, there is the higher
possibility of increasing a fabrication cost of the active-matrix
type device, as compared to that of the passive-matrix type device.
In such a case, a disadvantage of increasing a price of an
electrical apparatus employing the active-matrix type
light-emitting device in its display section may arise.
[0011] Thus, the present invention is intended to reduce a
fabrication cost of the active-matrix type display device so as to
provide an inexpensive display device. In addition, the present
invention is also intended to provide an inexpensive electrical
apparatus that employs in its display section, the display device
in accordance with the present invention.
SUMMARY OF THE INVENTION
[0012] In accordance with the present invention, in order to reduce
a fabrication cost of an active-matrix type display device, all of
the TFIs to be used in a pixel section are provided as a TFT of one
conductivity type (indicating herein either a p-channel TFT or an
n-channel TFT), and furthermore, a driver circuit is also formed
entirely with TFTs of the same conductivity type as in the pixel
section. Thus, a fabrication process can be significantly reduced,
and therefore, the fabrication cost can be reduced.
[0013] For the above purpose, in accordance with one aspect of the
present invention, all of a source wiring, a gate electrode, a gate
wiring (which is a line that transmits a signal to the gate
electrode), and a current supply line are simultaneously formed. In
other word, an identical electrically conductive (hereinafter
simply referred to as "conductive") film is formed on the same
surface. In addition, in accordance with another aspect of the
present invention, a line (referred to as the connecting wiring in
the present specification) that connects the TFT to a line for
connecting a plurality of independently formed gate wirings to each
other, or the source wiring, or the current supply line, is formed
on the same surface with the identical conductive film as the drain
wiring of the current-controlling TFT.
[0014] Furthermore, in accordance with a further important aspect
of the present invention, a driver circuit is formed of TFTs of one
and the same conductivity type. In other word, in contrast to the
conventional driver circuit that is in general designed based on a
CMOS circuit in which an n-channel TFT and a p-channel TFT are
complimentarily combined to each other, the driver circuit in
accordance with the present invention is formed by combining only
the p-channel TFTs or the n-channel TFTs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the accompanying drawings:
[0016] FIG. 1 shows a structure of a gate-side driver circuit;
[0017] FIG. 2 shows a timing chart of decoder input signals;
[0018] FIG. 3 shows a structure of a source-side driver
circuit;
[0019] FIG. 4 shows a circuit structure of a pixel section of a
light-emitting device;
[0020] FIG. 5 shows a cross-sectional structure of the pixel
section of the light-emitting device;
[0021] FIG. 6 shows a top-view structure of the pixel section of
the light-emitting device;
[0022] FIGS. 7(A) and 7(B) each show another cross-sectional
structure of the pixel section of the light-emitting device;
[0023] FIGS. 8(A) through 8(D) show various fabrication steps of
the light-emitting device;
[0024] FIGS. 9(A) through 9(C) show various fabrication steps of
the light-emitting device;
[0025] FIG. 10 shows another circuit structure of a pixel section
of a light-emitting device;
[0026] FIG. 11 shows yet another circuit structure of a pixel
section of a light-emitting device;
[0027] FIGS. 12(A) through 12(C) show various fabrication steps of
the light-emitting device;
[0028] FIG. 13 shows another top-view structure of the pixel
section of the light-emitting device;
[0029] FIGS. 14(A) through 14(C) show various fabrication steps of
the light-emitting device;
[0030] FIG. 15(A) shows yet another top-view structure of the pixel
section of the light-emitting device;
[0031] FIG. 15(B) shows yet another cross-sectional structure of
the pixel section of the light-emitting device;
[0032] FIGS. 16(A) and 16(B) show yet other circuit structures of a
pixel section of a light-emitting device;
[0033] FIGS. 17(A) and 17(B) show yet other circuit structures of a
pixel section of a light-emitting device;
[0034] FIG. 18 shows a thin film forming apparatus for forming an
EL layer;
[0035] FIGS. 19(A) and 19(B) show external appearances of a liquid
crystal display device;
[0036] FIGS. 20(A) through 20(F) show specific examples of an
electrical apparatus, respectively; and
[0037] FIGS. 21(A) through 21(D) show specific examples of an
electrical apparatus, respectively;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] With now reference to FIGS. 1 and 2, a driver circuit to be
used in the present invention will be described. In accordance with
the present invention, instead of a typical shift register, a
decoder employing p-channel TFTs as shown in FIG. 1 is used. FIG. 1
illustrates an example of a gate-side driver circuit.
[0039] In FIG. 1, reference numeral 100 denotes a decoder in the
gate-side driver circuit, and 101 denotes a buffer section of the
gate-side driver circuit. Here, the buffer section refers to a
section in which a plurality of buffers (buffer amplifiers) are
integrated. Furthermore, the buffer refers to a circuit capable of
exhibiting the driving capability without providing any adverse
effects of a subsequent stage on a previous stage.
[0040] The gate-side decoder 100 will be now described. Reference
numeral 102 denotes input signal lines (hereinafter referred to as
the selection lines) of the decoder 100, and more specifically
indicates A1, A1 bar (a signal having an inverted polarity with
respect to A1), A2, A2 bar (a signal having an inverted polarity
with respect to A2), . . . , An, and An bar (a signal having an
inverted polarity with respect to An). In other word, it can be
considered that the 2n selection lines are arranged.
[0041] The number of the selection lines is determined based on the
number of gate wirings to be output from the gate-side driver
circuit. For example, in the case where a pixel section for VGA
display is provided, 480 gate wirings are required, which in turn
requires a total of 18 selection lines to be provided for 9 bits
(corresponding to the case where n=9). The selection lines 102
transmit signals shown in the timing chart in FIG. 2. As shown in
FIG. 2, assuming that a frequency of A1 is normalized to be 1, a
frequency of A2 can be expressed as 2.sup.-1, a frequency of A3 can
be expressed as 2.sup.-2, and a frequency of An can be expressed as
2.sup.-(n-1).
[0042] Reference numeral 103a denotes a first-stage NAND circuit
(also referred to as the NAND cell), while 103b and 103c denote a
second-stage and an n-th stage NAND circuits, respectively. The
required number of the NAND circuits is equal to the number of the
gate wirings, and specifically, n NAND circuits are required here.
In other word, the decoder 100 in accordance with the present
invention is composed of a plurality of the NAND circuits.
[0043] In each of the NAND circuits 103a to 103c, p-channel TFTs
104 to 109 are combined to form a NAND circuit. Actually, 2n TFTs
are employed in each of the NAND circuits 103. Furthermore, a gate
of each of the p-channel TFTs 104 to 109 is connected to either one
of the selection lines 102 (A1, A1 bar, A2, A2 bar, . . . , An, An
bar).
[0044] In this case, in the NAND circuit 103a, the p-channel TFTs
104 to 106 that respectively have the gates connected to any of A1,
A2, . . . , An (which are referred to as the positive selection
lines) are connected to each other in parallel, and further
connected to a positive power source wiring (V.sub.DH) 110 as a
common source, as well as to an output line 111 as a common drain.
On the other hand, the remaining p-channel TFTs 107 to 109 that
respectively have the gates connected to any of A1 bar, A2 bar, . .
. , An bar (which are referred to as the negative selection lines)
are connected to each other in series, and a source of the
p-channel TFT 109 positioned at one end of the circuit is connected
to a negative power source wiring (V.sub.DL) 112 while a drain of
the p-channel TFT 107 positioned at the other end of the circuit is
connected to the output line 111.
[0045] As described in the above, the NAND circuit in accordance
with the present invention includes the n TFTs of one conductivity
type (the p-channel TFTs in this case) connected in series and the
other n TFTs of the one conductivity type (the p-channel TFTs in
this case) connected in parallel. It should be noted that in the n
NAND circuits 103a to 103c, all of combinations among the p-channel
TFTs and the selection lines are different from each other. In
other word, the output lines 111 are configured so that only one of
them is selected, and signals are input to the selection lines such
that the output lines 111 are sequentially selected from one side
thereof.
[0046] Then, the buffer 101 is composed of a plurality of buffers
113a to 113c so as to respectively correspond to the NAND circuits
103a to 103c. It should be noted that the buffers 113a to 113c may
have the same structure.
[0047] Furthermore, the buffers 113a to 113c are formed with
p-channel TFTs 114 to 116 as TFTs of one conductivity type. The
output line 111 from the decoder is input as a gate of the
corresponding p-channel TFT 114 (a first TFT of the one
conductivity type). The p-channel TFT 114 utilizes a ground power
source wiring (GND) 117 as its source, and a gate wiring 118 as its
drain. Moreover, the p-channel TFT 115 (a second TFT of the one
conductivity type) utilizes the ground power source line 117 as its
gate, a positive power source line (V.sub.DH) 119 as its source,
and the gate wiring 118 as its drain. The p-channel TFT 115 is
always in the ON state.
[0048] In other words, each of the buffers 113a to 113c in
accordance with the present invention includes the first TFT of the
one conductivity type (the p-channel TFT 114), and further includes
the second TFT of the one conductivity type (the p-channel TFT 115)
that is connected to the first TFT of the one conductivity type in
series and utilizes the gate of the first TFT of the one
conductivity type as the drain.
[0049] Furthermore, the p-channel TFT 116 (a third TFT of the one
conductivity type) employs a reset signal line (Reset) as its gate,
the positive power source line 119 as its source, and the gate
wiring 118 as its drain. It should be noted that the ground power
source line 117 may be replaced with a negative power source line
(which is a power source line for providing a voltage that causes a
p-channel TFT, to be used as a switching element of a pixel, to be
in the ON state).
[0050] In this case, a channel width (indicated as W1) of the
p-channel TFT 115 and a channel width (indicated as W2) of the
p-channel TFT 114 satisfy the relationship of W1<W2. The channel
width refers to a length of a channel formation region measured in
the direction perpendicular to a channel length.
[0051] The buffer 113a operates as follows. During a time period in
which a positive voltage is being applied to the output line 111,
the p-channel TFT 114 is in the OFF state (i.e., its channel is not
formed). On the other hand, since the p-channel TFT 115 is always
in the ON state (i.e., its channel is formed), a voltage of the
positive power source line 119 is applied to the gate wiring
118.
[0052] On the other hand, in the case where a negative voltage is
applied to the output line 111, the p-channel TFT 114 comes into
the ON state. In this case, since the channel width of the
p-channel TFT 114 is wider than that of the p-channel TFT 115, the
electrical potential of the gate wiring 118 is pulled by an output
on the side of the p-channel TFT 114, thereby resulting in the
electrical potential of the ground power source line 117 being
applied to the gate wiring 118.
[0053] Accordingly, the gate wiring 118 outputs a negative voltage
(that causes the p-channel TFT, to be used as the switching element
of the pixel, to be in the ON state) when a negative voltage is
being applied onto the output line 111, while always outputting a
positive voltage (that causes the p-channel TFT, to be used as the
switching element of the pixel, to be in the OFF state) when a
positive voltage is being applied onto the output line 111.
[0054] The p-channel TFT 116 is used as a reset switch for forcing
the gate wiring 118, to which the negative voltage is being
applied, to be pulled up to a positive voltage. Namely, after a
selection period of the gate wiring 118 is completed, a reset
signal is input so that a positive voltage is applied to the gate
wiring 118. It should be noted that the p-channel TFT 116 maybe
omitted.
[0055] With the gate-side driver circuit that operates in the
above-described manner, the gate wirings are sequentially selected.
Then, the structure of a source-side driver circuit is shown in
FIG. 3. The source-side driver circuit as shown in FIG. 3 includes
a decoder 301, a latch 302, and a buffer 303. Since the decoder 301
and the buffer 303 have the identical structures with those of the
gate-side driver circuit, respectively, descriptions therefor are
omitted here.
[0056] In the case of the source-side driver circuit shown in FIG.
3, the latch 302 is composed of a first-stage latch 304 and a
second-stage latch 305. Each of the first-stage latch 304 and the
second-stage latch 305 includes a plurality of basic units 307 each
composed of m p-channel TFTs 306a to 306c. An output line 308 from
the decoder 301 is input to gates of the respective m p-channel
TFTs 306a to 306c that form the basic unit 307. It should be noted
that the number m is any integer.
[0057] For example, in the case of the VGA display, the number of
the source wirings is 640. In the case where m=1, the number of the
NAND circuits required to be provided is also 640, while 20
selection lines (corresponding to 10 bits) are required to be
provided. On the other hand, however, when m=8, the number of the
necessary NAND circuits is 80 and the number of the necessary
selection lines is 14 (corresponding to 7 bits). Namely, assuming
that the number of the source wirings is M, the number of necessary
NAND circuits can be expressed as M/m.
[0058] Sources of the p-channel TFTs 306a to 306c are connected to
video signal lines (V1, V2, . . . , Vk) 309, respectively. Namely,
when a negative voltage is applied to an output line 308, all of
the p-channel TFTs 306a to 306c are simultaneously put into the ON
state, so that video signals are taken into the corresponding
p-channel TFTs 306a to 306c, respectively. The video signals thus
taken in are retained in capacitors 310a to 310c, respectively,
connected thereto.
[0059] Furthermore, the second-stage latch 305 also includes a
plurality of basic units 307b each composed of m p-channel TFTs
311a to 311c. All of gates of the p-channel TFTs 311a to 311c are
connected to a latch signal line 312, so that when a negative
voltage is applied to the latch signal line 312, all of the
p-channel TFTs 311a to 311c are simultaneously turned on.
[0060] As a result, the signals retained in the capacitors 310a to
310c are then retained respectively in capacitors 313a to 313c
connected to the p-channel TFTs 311a to 311c and simultaneously
output to the buffer 303. Then, as described with reference to FIG.
1, those signals are output to the source wirings 314 via the
buffer. With the source-side driver circuit that operates in the
above-described manner, the source wirings are sequentially
selected.
[0061] As described in the above, by composing the gate-side driver
circuit and the source-side driver circuit only of the p-channel
TFTs, all of the pixel sections and the driver circuits can be
entirely formed of the p-channel TFTs. Accordingly, upon
fabrication of an active-matrix type display device, a fabrication
yield and a throughput of the TFT steps can be significantly
improved, thereby resulting in a reduced fabrication cost.
[0062] It should be noted that the present invention can be
embodied even in the case where either of the source-side driver
circuit or the gate-side driver circuit, or both of them, are
provided in an IC chip to be externally attached.
Embodiment 1
[0063] In the present invention, the pixel section, in addition to
the driver circuit, is entirely composed of the p-channel TFTs.
Thus, in the present embodiment, the structure of the pixel section
for displaying an image in accordance with the signals transmitted
by the driver circuit as shown in FIGS. 1 and 3 will be
described.
[0064] The structure of a pixel of an active-matrix type
light-emitting device in accordance with the present invention is
shown in FIGS. 5 and 6. FIG. 5 illustrates a cross-sectional view
of one pixel, while FIG. 6 illustrates a top view of adjacent two
pixels. FIG. 5 shows a cross-sectional view cut along A-A' in FIG.
6, and the same component is designated with the same reference
numeral in both of these figures. In addition, the two pixels
illustrated in FIG. 6 are symmetric to each other with respect to
the current supply line 525, and therefore, have the same structure
as each other.
[0065] In FIG. 5, reference numeral 501 denotes a substrate
transparent to visible light, and 502 denotes an insulating film
containing silicon. As the substrate 501 that is transparent to
visible light, a glass substrate, a quartz substrate, a crystalline
glass substrate, or a plastic substrate (including a plastic film)
can be used. As the insulating film 502 containing silicon, a
silicon oxide film, a silicon oxynitride film, or a silicon nitride
film can be used.
[0066] In the present specification, TFTs are formed on an
insulating surface. As the insulating surface, an insulating film
(typically an insulating film containing silicon) or a substrate
made of an insulating body (typically a quartz substrate) may be
used. Accordingly, the expression "on the insulating surface" means
"on the insulating film" or "on the substrate made of the
insulating material".
[0067] On the insulating film 502 containing silicon, a switching
TFT 601 and a current-controlling TFT 602 are formed with p-channel
TFTs.
[0068] The switching TFT 601 employs, as an active layer, a
semiconductor region that includes regions 503 to 505 made of
p-type semiconductor (hereinafter referred to as the p-type
semiconductor regions) and regions 506 and 507 made of intrinsic or
substantially intrinsic semiconductor (hereinafter referred to as
the channel formation regions). On the other hand, the
current-controlling TFT 602 employs, as an active layer, a
semiconductor region including p-type semiconductor regions 508 and
509 and a channel formation region 510.
[0069] The p-type semiconductor region 503 or 505 serves as a
source region or a drain region of the switching TFT 601.
Furthermore, the p-type semiconductor region 508 serves as a source
region of the current-controlling TFT 602, while the p-type
semiconductor region 509 serves as a drain region of the
current-controlling TFT 602.
[0070] The active layers of the switching TFT 601 and the
current-controlling TFT 602 are covered with a gate insulating film
511, and further thereon, a source wiring 512, a gate electrode
513a, a gate electrode 513b, a drain wiring 514, and a gate
electrode 515 are formed. These components are simultaneously
formed with the identical material. As the constituent material for
these lines or electrodes, tantalum, tungsten, molybdenum, niobium,
titanium, or a nitride of these metals may be used. Alternatively,
an alloy in which these metals are combined, or a silicide of these
metals, may be used.
[0071] Furthermore, as shown in FIG. 6, the drain wiring 514 is
integrated with the gate electrode 515. In addition, the gate
electrodes 513a and 513b are integrated with the shared gate wiring
516, so that the same voltage is always being applied to these gate
electrodes 513a and 513b.
[0072] Moreover, in FIG. 5, reference numeral 517 denotes a
passivation film made of a silicon oxynitride film or a silicon
nitride film, and an interlayer insulating film 518 is formed
thereon. As the interlayer insulating film 518, an insulating film
containing silicon or an organic resin film is used. As the organic
resin film, a polyimide film, a polyamide film, an acrylic resin
film, or a BCB (benzocyclobutene) film can be used.
[0073] Further on the interlayer insulating film 518, connecting
wirings 519 to 522 and an electrode 523 made of a transparent
conductive film are formed. At the same time, line 524 as shown in
FIG. 6 are also simultaneously formed. As the transparent
conductive film, a thin film made of indium oxide, tin oxide, zinc
oxide, a compound of indium oxide and tin oxide, a compound of
indium oxide and zinc oxide, or a compound obtainable by adding
gallium to these materials can be used.
[0074] In this case, the connecting wiring 520 is a line that
provides electrical connection between the source wiring 512 and
the p-type semiconductor region 503, while the connecting wiring
521 is a line that provides electrical connection between the
p-type semiconductor region 505 and the drain region 514. Moreover,
the connecting wiring 522 is a line that provides electrical
connection between the source region 508 and the current supply
line (see FIG. 6) 525.
[0075] The connecting wiring 519 is a line that realizes
connections among the gate wirings 516 divided and formed into a
plurality of patterns, and is provided to overpass the source
wiring 512 and the current supply line 525. It is also possible to
connect the source wiring or the current supply line, divided into
a plurality of portions, with the connecting wiring formed so as to
overpass the gate wiring.
[0076] An electrode 523 is an anode of the EL element, and is
referred to as the pixel electrode or the anode in the present
specification. The pixel electrode 523 is electrically connected to
a drain region 509 of the current-controlling TFT 602. In FIG. 6,
the pixel electrode 523 can be considered as a drain wiring of the
current-controlling TFT 602.
[0077] FIG. 7(A) shows a cross-sectional view obtainable by cutting
FIG. 6 along B-B'. As shown in FIG. 7(A), the connecting wiring 524
overpasses the current supply line 525 and provides connection
among the gate wirings 516. In addition, FIG. 7(B) shows a
cross-sectional view obtainable by cutting FIG. 6 along C-C'. As
shown in FIG. 7(B), the connecting wiring 522 electrically connects
the p-type semiconductor region 508 of the current-controlling TFT
602 with the current supply line 525.
[0078] In the actual device, an EL layer (not shown) and a cathode
(not shown) are formed thereafter on the pixel electrode 523 to
complete an active-matrix type light-emitting device. The EL layer
and the cathode may be formed with any known technique.
[0079] Furthermore, although a TFT having a top-gate structure
(specifically, a planar-type TFT) has been described as an example
in the above, the present invention is not limited to such a kind
of TFT structure. Alternatively, the present invention can be
applied to a TFT having a bottom-gate structure. Typically, it is
possible to embody the present invention in a reverse-staggered
type TFT.
[0080] With the pixel structure as described in the above, the
fabrication process for the active-matrix type light-emitting
device can be significantly simplified, and an inexpensive
active-matrix type light-emitting device can be produced. In
addition, an electrical apparatus that employs the same as a
display section can be realized.
Embodiment 2
[0081] In the present embodiment, the fabrication process of an
active-matrix type light-emitting device in which a pixel section
and a driver circuit for transmitting a signal to the pixel section
are formed on the identical insulating surface will be described
with reference to FIGS. 8(A) to 8(D) and FIGS. 9(A) to 9(C).
[0082] First, as shown in FIG. 8(A), an underlying film (insulating
body) 802 is formed on a glass substrate 801. In the present
embodiment, the underlying film 802 is formed by sequentially
depositing a first silicon oxynitride film having a thickness of 50
nm and a second silicon oxynitride film having a thickness of 200
nm in this order from the side closer to the glass substrate 801.
The nitrogen content of the first silicon oxynitride film is larger
than that of the second silicon oxynitride film so as to suppress
diffusion of alkali metal from the glass substrate 801.
[0083] Then, an amorphous silicon film (not shown) is formed on the
underlying film 802 by a plasma CVD method to have a thickness of
40 nm. Thereafter, the amorphous silicon film is irradiated with
laser light for crystallization to form a polycrystalline silicon
film (polysilicon film) 803. It should be noted that a
microcrystalline silicon film or an amorphous silicon germanium
film may be formed instead of the amorphous silicon film. Moreover,
a method for crystallization is not limited to the laser
crystallization method, but any other known crystallization method
can be used.
[0084] Then, as shown in FIG. 8(B), the polycrystalline silicon
film 803 is patterned to form respective independently isolated
semiconductor layers 804 to 806. Upon completion, the semiconductor
layer denoted with reference numeral 804 becomes an active layer of
a TFT that forms a driver circuit (this TFT is referred to as
driver TFT). On the other hand, the semiconductor layer denoted
with reference numeral 805 becomes an active layer of the switching
TFT, while that denoted with reference numeral 806 denotes an
active layer of the current-controlling TFT.
[0085] Thereafter, a gate insulating film 807 with a thickness of
80 nm, made of a silicon oxide film, is formed by a plasma CVD
method so as to cover the isolated semiconductor layers 804 to 806.
Furthermore, a tungsten film (not shown) is formed by a sputtering
method on the gate insulating film 807 to have a thickness of 350
nm, and is then patterned to form gate electrodes 808, 809, 810a,
and 810b. Simultaneously, a source wiring 812 and a drain wiring
813 of the switching TFT are formed. Of course, the drain wiring
813 and the gate electrode 811 are formed integrally.
[0086] Then, elements belonging to Group 13 in the periodic table
are added with the gate electrodes 808, 809, 810a, 810b, the source
wiring 812 and the drain wiring 813 being used as a mask. Any known
methods may be used for the above purpose. In the present
embodiment, boron is added by a plasma doping method at the
concentration in the range of 5.times.10.sup.19 to
1.times.10.sup.21 atoms/cm.sup.3. Thus, the semiconductor regions
with the p-type conductivity (hereinafter referred to as the p-type
semiconductor regions) 814 to 821 are formed. Furthermore, channel
formation regions 822 to 826 are formed immediately below the gate
electrodes 808, 809, 810a, and 810b.
[0087] It should be noted that in the present embodiment, the
p-type semiconductor regions 814 and 816 serve as source regions of
the p-channel TFTs forming the driver circuit, while the p-type
semiconductor region 815 serves as a drain region of the p-channel
TFT forming the driver circuit.
[0088] Thereafter, a heat treatment is performed to activate the
elements in the Group 13 of the periodic table contained in the
p-type semiconductor regions. This activation process may be
performed by either one of a furnace annealing method, a laser
annealing method, and a lamp annealing method, or any combination
thereof. In the present embodiment, a heat treatment is performed
at 500.degree. C. for four (4) hours in nitrogen atmosphere. In
this case, it is preferable to reduce the concentration of oxygen
in the nitrogen atmosphere to as low a level as possible. The
active layers of the TFTs are formed by the above activation
process.
[0089] After the activation process is completed, a silicon
oxynitride film with a thickness of 200 nm is formed as a
passivation film 827, and a hydrogenation process for the
semiconductor layers is then performed. Any known hydrogen
annealing technique or a plasma hydrogenation technique may be used
for the hydrogenation process. Thus, the structure as shown in FIG.
8(C) can be obtained.
[0090] Thereafter, as shown in FIG. 8(D), an interlayer insulating
film 828 made of a resin is formed to have a thickness of 800 nm.
As the resin for this purpose, polyimide, polyamide, acrylic resin,
epoxy resin, or BCB (benzocyclobutene) may be used. Alternatively,
an inorganic insulating film may be also used.
[0091] Contact holes are then formed in the interlayer insulating
film 828, and connecting wirings 829 to 835 and a pixel electrode
836 are formed. In the present embodiment, a conductive film made
of a compound of indium oxide and tin oxide (Indium Tin Oxide; ITO)
is used for forming the connecting wirings 829 to 835 and the pixel
electrode 836. It should be noted that of course, any conductive
films made of other materials that are transparent to visible light
can be used for this purpose.
[0092] The connecting wirings 829 and 831 serve as source wirings
of the p-channel TFTs forming the driver circuit, while the
connecting wiring 830 serves as a drain wiring of the p-channel TFT
forming the driver circuit. Thus, in the present embodiment, the
driver circuit is formed based on a PMOS circuit which is formed of
p-channel TFTs.
[0093] In the above-described state, the p-channel TFTs forming the
driver circuit as well as the switching TFT and the
current-controlling TFT in the pixel section are completed. In the
present embodiment, all of the TFTs are of the p-channel type. It
should be noted that the switching TFT is formed such that the gate
electrode thereof overpasses the active layer at two different
positions so that the two channel formation regions are connected
to each other in series. Such a structure can effectively suppress
an OFF current value (i.e., a current that flows when a TFT is in
the OFF state).
[0094] Then, as shown in FIG. 9(A), insulating bodies 837 and 838
made of a resin are formed so as to cover edge portions and concave
portions (recesses formed due to the contact holes) of the pixel
electrode 836. These insulating bodies 837 and 838 may be formed by
forming an insulating film made of a resin and then patterning the
film. In this case, it is desirable to set a height (d) from the
surface of the pixel electrode 836 to the top of the insulating
body 838 to be at 300 nm or less (preferably 200 nm or less). It
should be noted that the insulating bodies 837 and 838 may be
omitted.
[0095] The insulating body 837 is formed for the purpose of
covering the edge portions of the pixel electrode 836 and thereby
avoiding an adverse effect of electric field concentration at the
edge portions. Thus, deterioration of the EL layer can be
prevented. On the other hand, the insulating body 838 is formed for
the purpose of burying the concave portions of the pixel electrode
which are formed due to the contact holes. Thus, any coverage
defect of the EL layer to be later formed can be prevented, and any
short-circuit between the pixel electrode and a cathode to be later
formed can be prevented.
[0096] Thereafter, an EL layer 839 with a thickness of 70 nm and a
cathode 840 with a thickness of 300 nm are formed by a vapor
deposition method. In the structure of the present embodiment, a
copper phthalocyanine layer (hole injection layer) with a thickness
of 20 nm and an Alg.sub.3 layer (light-emitting layer) with a
thickness of 50 nm are formed as the EL layer 839. It should be
noted that any other known structure in which a hole injection
layer, a hole transport layer, an electron transport layer or an
electron injection layer are combined may be used for the
light-emitting layer.
[0097] In the present embodiment, the copper phthalocyanine layer
is first formed to cover all of the pixel electrodes, and
thereafter, a red-color light-emitting layer, a green-color
light-emitting layer, or a blue-color light-emitting layer are
formed for each of the pixels corresponding to red, green and blue
colors, respectively. The regions to which the layer is to be
formed may be selected upon vapor deposition by means of a shadow
mask. Thus, a color display can be realized.
[0098] When the green-color light-emitting layer is to be formed,
Alq.sub.3 (tris-8-quinolinolato aluminum complex) is used as a
mother material of the light-emitting layer, and quinacridon or
coumarine 6 is used as a dopant. When the red-color light-emitting
layer is to be formed, Alq.sub.3 is used as a mother material of
the light-emitting layer, and DCJT, DCM1, or DCM2 is used as a
dopant. When the blue-color light-emitting layer is to be formed,
BAlq.sub.3 (a complex with five coordinations having a mixed ligand
of 2-methyl-8-quinolinol and phenol derivative) is used as a mother
material of the light-emitting layer, and perylene is used as a
dopant.
[0099] It should be noted that the present invention is not limited
to use of the above-mentioned organic materials, but rather, any
known low-molecule type organic EL material, high-molecule type
organic EL material, or inorganic EL material can be used.
Alternatively, any combination of these materials can be also used.
Furthermore, in the case where a high-molecule type organic EL
material is used, a coating method can be used.
[0100] In the manner as mentioned in the above, the EL element
composed of pixel electrode (anode) 836, EL layer 839 and cathode
840 is formed (see FIG. 9(B)).
[0101] Thereafter, a cover member 842 is bonded by means of an
adhesive 841. In the present embodiment, a glass substrate is used
as the cover member 842. Alternatively, a flexible plastic film, a
quartz substrate, a plastic substrate, a metal substrate, a silicon
substrate, or a ceramic substrate may be used. It is advantageous
to provide an insulating film containing silicon or a carbon film
on a surface exposed to the surrounding air so as to prevent oxygen
or water from entering or to provide protection against scratches
caused by friction.
[0102] As the adhesive 841, a UV curable resin or a thermosetting
resin is typically used. For example, PVC (polyvinyl chloride),
acrylic resin, polyimide, epoxy resin, silicone resin, PVB
(polyvinyl butyral), or EVA (ethylene vinyl acetate) can be used.
In the case where the adhesive 841 is positioned in the side closer
to an observer when viewed from the EL element, the adhesive is
required to be made of a material that allows light to pass
therethrough. In addition, it is advantageous to provide a
water-absorbing material (preferably barium oxide) and/or an
anti-oxidization material (i.e., a substance that adsorbs oxygen)
within the adhesive 841 for preventing deterioration of the EL
element.
[0103] With the above-described structure, the EL element can be
completely shut out from the ambient air. Thus, deterioration of
the EL material due to oxidation can be substantially completely
suppressed, so that reliability of the resultant EL element can be
significantly improved.
[0104] The active-matrix type light-emitting device thus fabricated
in the above-described manner has the pixel section that includes
the circuit structure as shown in FIG. 10. Specifically, in FIG.
10, reference numeral 1001 denotes a source wiring, 1002 denotes a
gate wiring, 1003 denotes a switching TFT, 1004 denotes a
current-controlling TFT, 1005 denotes a current supply line, and
1006 denotes an EL element. In the present embodiment, each of the
switching TFT 1003 and the current-controlling TFT 1004 is formed
as the p-channel TFT.
[0105] It should be noted that a gate capacitance of the
current-controlling TFT 1004 exhibits the same function as the
capacitor employed in the conventional art (i.e., the capacitor 404
in FIG. 4). This can be realized because in the case where a
time-divisional grayscale display is performed by means of a
digital driving scheme, necessary charges can be retained only by
the gate capacitance of the current-controlling TFT since one-frame
period (or one-field period) is short.
[0106] The active-matrix type light-emitting device of the present
invention as described in the above requires only five masks in
total for performing the patterning steps (this number can be
further reduced to four when the insulating bodies 837 and 838 are
omitted), which can in turn realize a high fabrication yield and a
low fabrication cost.
Embodiment 3
[0107] In Embodiment 2 mentioned in the above, the circuit
structure of the pixel section shown in FIG. 10 can be modified as
shown in FIG. 11. Specifically, in FIG. 11, reference numeral 1101
denotes a source wiring, 1102 denotes a gate wiring, 1103 denotes a
switching TFT, 1104 denotes a current-controlling TFT, 1105 denotes
a current supply line, and 1106 denotes an EL element. In the
present embodiment, each of the switching TFT 1103 and the
current-controlling TFT 1104 is formed as the p-channel TFT.
[0108] In this case, since the gate wiring 1102 and the current
supply line 1105 are disposed in different layers, it is
advantageous to provide these components so as to overlap each
other with an interlayer insulating film interposed therebetween.
Thus, an occupied area of these lines can be substantially made
common, and therefore, the effective light-emission area of the
pixel can be increased.
Embodiment 4
[0109] In the present embodiment, the active-matrix type
light-emitting device is fabricated in the manner different from
that described in Embodiment 1. The fabrication process will be
described below with reference to FIGS. 12(A) to 12(C).
[0110] First, the fabrication steps up to the one as shown in FIG.
8(D) are performed as described previously in connection with
Embodiment 2 to form connecting wirings 1201 to 1207 and a drain
wiring 1208. In the present embodiment, these connecting wirings
are formed of a metal film. Although any material can be used as
the metal film, a layered film having a three-layer structure in
which an aluminum film is sandwiched between titanium films is
employed in the present embodiment.
[0111] Then, as shown in FIG. 12(B), a pixel electrode 1209 made of
a transparent conductive film is formed. In this case, the pixel
electrode 1209 is formed such that a portion thereof comes into
contact with the drain wiring 1208. The current-controlling TFT and
the pixel electrode can be thus electrically connected to each
other. FIG. 13 shows a top view in the above-described structure.
It should be noted that the cross-sectional view shown in FIG.
12(B) is obtainable by cutting FIG. 13 along A-A'.
[0112] In the present embodiment, the connecting wirings 1201 to
1207 can be made of a metal film. Accordingly, as compared to the
transparent conducting film such as an ITO film or the like
described in the previous embodiment modes, a reduction in a wiring
resistance as well as a reduction in a contact resistance can be
realized. Moreover, all of the lines for connecting various circuit
portions in the driver circuit can be made of a low-resistance
metal film, and therefore, a driver circuit capable of exhibiting a
higher operating speed can be realized.
[0113] Although the pixel electrode 1209 is formed after the
connecting wirings 1201 to 1207 and the drain wiring 1208 are
completed, this fabrication order may be reversed. In other word,
the connecting wirings and the drain wiring made of a metal film
may be formed after the pixel electrode made of a transparent
conductive film is formed.
[0114] Thereafter, as in Embodiment 2, an insulating body 1210 made
of a resin is formed, and an EL layer 1211 and a cathode 1212 are
sequentially formed. Furthermore, a cover member 1214 is formed
with an adhesive 1213. Thus, the active-matrix type light-emitting
device as shown in FIG. 12(C) is completed.
Embodiment 5
[0115] In the present embodiment, an example of fabricating the
active-matrix type light-emitting device in accordance with the
present invention with a plastic substrate or a plastic film will
be explained. Plastics that can be used in the present embodiment
include PES (polyethylene sulfile), PC (polycarbonate), PET
(polyethylene terephthalate), or PEN (polyethylene
naphthalate).
[0116] First, the TFTs and the EL element are formed on the glass
substrate 801 in accordance with the fabrication steps as described
in Embodiment 2. In the present embodiment, however, a peeling
layer 1401 is formed between the glass substrate 801 and the
underlying film 802. A semiconductor film can be used as the
peeling layer 1401. Typically, an amorphous silicon film may be
used for the above purpose.
[0117] Moreover, in the present embodiment, a cover member 1403 is
adhered by means of a first adhesive 1402. An insulating film made
of a resin (typically, polyimide, acrylic resin, polyamide, or
epoxy resin) is used as the first adhesive 1402. It should be noted
that the material for the first adhesive 1402 is required to
realize a sufficient selection ratio upon etching of the peeling
layer 1401 by means of a gas containing halogen fluoride. As the
cover member 1403 to be adhered with the first adhesive 1402, a PET
film is used in the present embodiment.
[0118] Then, the entire substrate on which the element has been
formed is exposed to the gas containing halogen fluoride. This
treatment allows the peeling layer 1401 to be selectively removed.
Halogen fluoride refers to a substance that can be expressed as the
chemical formula of XFn (where X indicates a halogen other than
fluorine, and n is an integer). For example, as the halogen
fluoride, chlorine monofluoride (ClF), chlorine trifluoride
(ClF.sub.3), bromine monofluoride (BrF), bromine trifluoride
(BrF.sub.3), iodine monofluoride (IF), iodine trifluoride
(IF.sub.3) can be used.
[0119] Halogen fluoride exhibits a large selection ratio between a
silicon film and a silicon oxide film, thereby resulting in a
selective etching of the silicon film being realized. Furthermore,
this etching reaction can easily proceed at room temperature, and
therefore, the process can be performed even after the EL element
with low heat-resistance capability is formed.
[0120] Although the silicon film can be etched only by being
exposed to the above-mentioned halogen fluoride, other fluorides
(carbon tetrafluoride (CF.sub.4) or nitrogen trifluoride) may be
used in the present invention so long as they are put into a plasma
condition.
[0121] In the present embodiment, chlorine trifluoride (ClF.sub.3)
is used as halogen fluoride and nitrogen is used for a dilution
gas. Argon, helium, or neon may be used as the dilution gas. Flow
rates of both of the gases may be set at 500 sccm
(8.35.times.10.sup.-6 m.sup.3/s), and a reaction pressure may be
set in the range from 1 to 10 Torr (1.3.times.10.sup.2 to
1.3.times.10.sup.3 Pa). Moreover, a treatment temperature may be
set at room temperature (typically in the range from 20 to
27.degree. C.).
[0122] Thereafter, as shown in FIG. 14(C), a substrate (bonding
substrate) 1405 made of a plastic substrate or a plastic resin is
adhered by means of a second adhesive 1404. In the present
embodiment, a PET film is used as the bonding substrate 1405. It is
desirable for the cover member 1403 and the bonding substrate 1405
to be made of the same material as each other in order to satisfy a
stress balance condition.
[0123] Thus, the active-matrix type light-emitting device in which
the TFTs and the EL element are sandwiched by the plastic film can
be obtained. Since the plastic film is bonded after the TFTs are
formed in the present embodiment, no limitation is applied onto the
fabrication process. For example, the TFTs can be formed without
taking the heat-resistance capability of the plastic to be employed
into consideration.
[0124] Furthermore, since a flexible, light-weighted light-emitting
device can be obtained, the device in the present embodiment is
suitable to a display section of portable information equipment
such as a mobile phone, an electronic databook or the like.
[0125] The structure as described in the present embodiment can be
freely combined with any structures in Embodiments 1 through 4.
Embodiment 6
[0126] In the present invention, it is advantageous to provide a
DLC (diamond-like carbon) film on one side or both sides of the
substrate or the cover member on which the TFTs and the EL element
are to be formed. It should be noted that a thickness of such a DLC
film is desirably not greater than 50 nm (more preferably in the
range of 10 to 20 nm) since too large a thickness thereof causes
transmittance of the film to be reduced. In addition, the DLC film
may be formed by a sputtering method or an ECR plasma CVD
method.
[0127] The DLC film is characterized by the Raman spectrum
distribution including an asymmetric peak at around 1550 cm.sup.-1,
and a shoulder at around 1300 cm.sup.-. Moreover, the DLC film is
also characterized by the hardness in the range of 15 to 25 Pa when
measured by means of a micro-hardness tester. Furthermore, it is
advantageous to provide the DLC film as a protection film for
surface protection and/or heat dissipation since the DLC film has a
larger hardness and a larger heat conductivity as compared to the
substrate or the cover member.
[0128] The structure as described in the present embodiment can be
freely combined with any structures in Embodiments 1 through 5.
Embodiment 7
[0129] In the present embodiment, external appearance views of the
light-emitting device of the present invention as described in
Embodiment 2 will be described. FIG. 15(A) shows a top view of the
light-emitting device of the present invention, while FIG. 15(B)
shows a cross-sectional view thereof.
[0130] In FIG. 15(A), reference numeral 1501 denotes a substrate,
1502 denotes a pixel section, 1503 denotes a source-side driver
circuit, and 1504 denotes a gate-side driver circuit. Each of these
driver circuits is connected via a wiring 1505 to an FPC (flexible
printed circuit) 1506, which in turn is connected to an external
apparatus. The gate-side driver circuit shown in FIG. 1 is used in
the gate-side driver circuit 1504 in FIG. 15(A), while the
source-side driver circuit shown in FIG. 3 is used in the
source-side driver circuit 1503 in FIG. 15(A). Furthermore, the
pixel section shown in FIG. 5 is used in the pixel section 1502 in
FIG. 15(A). In this case, a first sealing member 1511, a cover
member 1512, an adhesive 1513 (see FIG. 15(B)), and a second
sealing member 1514 are formed so as to surround the pixel section
1502, the source-side driver circuit 1503, and the gate-side driver
circuit 1504.
[0131] FIG. 15(B) corresponds to the cross-sectional view
obtainable by cutting FIG. 15(A) along A-A'. In this case, a region
surrounded with a dashed line 1500 corresponds to the
cross-sectional view shown in FIG. 9(C), and accordingly, any
detailed descriptions thereof will be omitted here.
[0132] A cathode of the EL element is electrically connected to the
wiring 1505 in the region denoted by reference numeral 1514. The
wiring 1505 is provided to supply a predetermined voltage to the
cathode, and is electrically connected to the FPC 1506 via an
anisotropic conductive film 1515. Furthermore, the EL element is
surrounded with the first sealing member 1511 and the cover member
1512 which is bonded to the substrate 1501 by the first sealing
member 1511. The EL element is encapsulated with an adhesive
1513.
[0133] Furthermore, a spacer may be contained in the adhesive 1513.
In this case, if the spacer is formed of barium oxide, it is
possible to allow the spacer itself to have water-absorbing
capability. In the case where the spacer is provided, it is
advantageous to provide on a cathode, a resin film as a buffer
layer for mitigating a pressure from the spacer.
[0134] The wiring 1505 is electrically connected to the FPC 1506
via the anisotropic conductive film 1515. The wiring 1505 transmits
to the FPC 1506 the signal to be sent to the pixel section 1502,
the source-side driver circuit 1503, and the gate-side driver
circuit 1504. The wiring 1505 is electrically connected to the
external apparatus by the FPC 1506.
[0135] Furthermore, in the present embodiment, the second sealing
member 1514 is provided to cover an exposed portion of the first
sealing member 1511 and a portion of the FPC 1506, so that the EL
element can be completely shut out from the ambient air. The
light-emitting device having the cross-sectional structure shown in
FIG. 15(B) is thus obtained. The light-emitting device in the
present embodiment can be freely combined with any structures in
Embodiments 1 through 6.
Embodiment 8
[0136] In the present embodiment, the pixel structure of the
light-emitting device in accordance with the present invention will
be described with reference to FIGS. 16(A) and 16(B). In the
present embodiment, reference numeral 1601 denotes a source wiring
of a switching TFT 1602, 1603 denotes a gate wiring of the
switching TFT 1602. 1604 denotes a current-controlling TFT, 1605
denotes a capacitor (that can be omitted), 1606 denotes a current
supply line, 1607 denotes a power source controlling TFT. 1608
denotes an EL element, and 1609 denotes a power source controlling
line. In this case, the source wiring 1601, the gate wiring 1603,
the current supply line 1606, and the power source controlling line
1608 are formed of the identical conductive film in the same
layer.
[0137] With respect to operations of the power source controlling
TFT 1607, reference can be made to Japanese Patent Application No.
11-341272. It should be noted that in the present embodiment, the
power source controlling TFT is formed as the p-channel type that
has the structure identical to that of the current-controlling
TFT.
[0138] Although the power source controlling TFT 1607 is provided
between the current-controlling TFT 1604 and the EL element 1608 in
the present embodiment, it is also possible to provide the
current-controlling TFT 1604 between the power source controlling
TFT 1607 and the EL element 1608. Furthermore, the power source
controlling TFT 1607 is preferably formed to have the identical
structure with the current-controlling TFT 1604, or to be connected
in series with the current-controlling TFT 1604 while utilizing the
identical active layer thereto.
[0139] FIG. 16(A) illustrates an example in which the current
supply line 1606 is shared with the two pixels. More specifically,
the two pixels are formed to be symmetric to each other with
respect to the current supply line 1606. In this case, the number
of the necessary current supply lines can be reduced, and thus the
pixel section can be formed with higher precision. On the other
hand, FIG. 16(B) illustrates an example in which the current supply
line 1610 is arranged in parallel to the gate wiring 1603, while
the current controlling line 1611 is arranged in parallel to the
source wiring 1601.
[0140] The structure as described in the present embodiment can be
freely combined with any structures in Embodiments 1 through 7.
Embodiment 9
[0141] In the present embodiment, the pixel structure of the
light-emitting device in accordance with the present invention will
be described with reference to FIGS. 17(A) and 17(B). In the
present embodiment, reference numeral 1701 denotes a source wiring
of a switching TFT 1702, 1703 denotes a gate wiring of the
switching TFT 1702, 1704 denotes a current-controlling TFT, 1705
denotes a capacitor (that can be omitted), 1706 denotes a current
supply line, 1707 denotes an erasing TFT, 1708 denotes an erasing
gate wiring, and 1709 denotes an EL element. In this case, the
source wiring 1701, the gate wiring 1703, the current supply line
1706, and the erasing gate wiring 1708 are formed of the identical
conductive film in the same layer.
[0142] With respect to operations of the erasing TFT 1707,
reference can be made to Japanese Patent Application No. 11-338786.
It should be noted that in the present embodiment, the power source
controlling TFT is formed as the p-channel type that has the
structure identical to that of the current-controlling TFT. In the
above-mentioned Japanese Patent Application. No. 11-338786, the
erasing gate wiring is referred to as the erasing gate signal
line.
[0143] A drain of the erasing TFT 1707 is connected to a gate of
the current-controlling TFT 1704, so that a gate voltage of the
current-controlling TFT 1704 can be forceably changed. It is
preferable to form the erasing TFT 1707 as a p-channel TFT that has
the same structure as the switching TFT 1702 so that an OFF current
can be reduced.
[0144] FIG. 17(A) illustrates an example in which the current
supply line 1706 is shared between the two pixels. Namely, the two
pixels are formed to be symmetric to each other with respect to the
current supply line 1706. In this case, the number of the necessary
current supply lines can be reduced, and thus the pixel section can
be formed with higher precision. On the other hand, FIG. 17(B)
illustrates an example in which the current supply line 1710 is
arranged in parallel to the gate wiring 1703, while the erasing
gate wiring 1711 is arranged in parallel to the source wiring
1701.
[0145] The structure as described in the present embodiment can be
freely combined with any structures in Embodiments 1 through 7.
Embodiment 10
[0146] The light-emitting device in accordance with the present
invention may have a structure in which several TFTs are provided
in one pixel. Although Embodiments 8 and 9 have described examples
in which the three TFTs are provided in one pixel, four through six
TFTs may be provided. The present invention is not limited to the
pixel structure of the light-emitting device, but can be embodied
in other structures.
[0147] The structure as described in the present embodiment can be
freely combined with any structures in Embodiments 1 through 7.
Embodiment 11
[0148] In the present embodiment, a film formation apparatus to be
used for forming the EL layer and the cathode will be described
with reference to FIG. 18. Specifically, in FIG. 18, reference
numeral 1801 denotes a transportation chamber (A) in which a
transportation chamber (A) 1802 is provided for realizing
transportation of a substrate 1803. The transportation chamber (A)
1801 includes a reduced-pressure atmosphere, and is blocked from
other treatment chambers by means of gates. The substrate is passed
from the transportation chamber (A) 1801 to the other treatment
chambers by means of a transportation mechanism (A) when the
corresponding gate is opened.
[0149] A cryopump is used to reduce the pressure in the
transportation chamber (A) 1801. An exhaust port 1804 is provided
on a side surface of the transportation chamber (A) 1801, and the
exhaust pump is disposed below the exhaust port 1804. Such a
structure realizes an advantage in that a maintenance operation of
the exhaust pump can be easily performed.
[0150] The respective treatment chambers will be described below.
Since the transportation chamber (A) 1801 is provided with the
reduced-pressure atmosphere, all of the treatment chambers that are
directly coupled thereto are provided with an exhaust pump (not
illustrated). As the exhaust pump, an oil rotary pump, a mechanical
booster pump, a turbo molecular pump, or a cryopump can be
used.
[0151] Reference numeral 1805 denotes a stock chamber in which a
substrate is set (mounted). This chamber is also referred to as a
load-lock chamber. The stock chamber 1805 is shielded from the
transportation chamber (A) 1801 by a gate 1800a, and a carrier (not
illustrated) to which the substrate 1803 is set is disposed in this
chamber 1805. Furthermore, the stock chamber 1805 is provided with
the above-mentioned exhaust pump as well as a purge line for
introducing a nitrogen gas or an inert gas with high purity to the
stock chamber 1805.
[0152] In the present embodiment, the substrate 1803 is set onto
the carrier with an element formation surface being faced-down.
This is intended to facilitate the face-down orientation when films
are formed by a vapor deposition method later. In the face-down
orientation, films are formed on the substrate with the element
formation surface of the substrate being facing downward. This
orientation can suppress attachment of dust on the element
formation surface of the substrate.
[0153] Reference numeral 1806 denotes a transportation chamber (B),
that is coupled to the stock chamber 1805 via a gate 1800b. The
transportation chamber (B) 1806 is provided with a transportation
mechanism (B) 1807. Reference numeral 1808 denotes a baking chamber
(bake chamber), that is coupled to the transportation chamber (B)
1806 via a gate 1800c.
[0154] The baking chamber 1808 is provided with a mechanism for
inverting the substrate orientation in the upside-down manner.
Namely, the substrate that has been transported in the face-down
orientation is once changed into a face-up orientation in the
baking chamber 1808. This is intended to allow a treatment in the
subsequent spin coater chamber 1809 to be performed in the face-up
orientation. After the treatment in the spin coater chamber 1809 is
completed, the substrate is returned to the baking chamber 1808 to
be again inverted upside-down into the face-down orientation, and
then further returned to the stock chamber 1805.
[0155] The spin coater chamber 1809 is coupled to the
transportation chamber (B) 1806 via a gate 1800d. The spin coater
chamber 1809 is a film formation chamber for forming a film
containing an EL material by applying a solution containing the EL
material onto the substrate. In the spin coater chamber 1809, a
high-molecule type (polymer type) organic EL material is mainly
formed. In this case, the film formation chamber is always filled
with an inert gas such as nitrogen or argon. In particular, when a
film is formed in the increased-pressure atmosphere at 1 to 5 atoms
(preferably 1.5 to 3 atoms), it is possible to effectively prevent
oxygen or water from entering the film formation chamber.
[0156] The EL material to be formed includes, not only that to be
used as a light-emitting layer, but also that to be used as an
electron injection layer or an electron transport layer. Any known
high-molecule type organic EL material can be also used. Typical
organic EL materials for serving as the light-emitting layer
include PPV (polyparaphenylene vinylene) derivative, PVK (polyvinyl
carbazole) derivative or polyfluorene derivative. These materials
are also referred to as .pi.-conjugated polymer. Furthermore, as
the electron injection layer, PEDOT (polythiophene) or PAni
(polyaniline) can be used.
[0157] Reference numeral 1810 denotes a treatment chamber for
performing a surface treatment to an anode or a cathode to serve as
the pixel electrode of the EL element (hereinafter, this chamber is
referred to as the pre-treatment chamber). The pre-treatment
chamber 1810 is shielded from the transportation chamber (A) 1801
by a gate 1800e. The pre-treatment chamber can be modified in
various manners based on the fabrication process of the EL element
to be conducted. In the present embodiment, the pre-treatment
chamber 1810 is configured to heat the pixel electrode at 100 to
120 C while irradiating the surface thereof with UV-light. Such a
pre-treatment is effective when the anode surface of the EL element
is to be processed.
[0158] Reference numeral 1811 denotes a vapor deposition chamber
for forming the conductive film or the EL material by a vapor
deposition method. The vapor deposition chamber 1811 is coupled to
the transportation chamber (A) 1801 via a gate 1800f. The vapor
deposition chamber 1811 can be provided therein with a plurality of
vapor deposition sources. In addition, it is also possible to cause
the vapor deposition sources to be evaporated by resistive-heating
or electron beams to form the intended film.
[0159] The conductive film to be formed in the vapor deposition
chamber 1811 is provided as an electrode on the cathode side of the
EL element. For this purpose, a metal having a relatively small
work function, typically an element belonging to Group 1 or Group 2
in the periodic table (typically, lithium, magnesium, cesium,
calcium, potassium, barium, sodium, or beryllium), or a metal
having a work function which is close to those thereof can be
deposited. Alternatively, aluminum, copper, or silver can be
deposited to form a low-resistance conductive film. Furthermore, a
conductive film made of a compound of indium oxide and tin oxide,
or a conductive film made of a compound of indium oxide and zinc
oxide, can be formed by the vapor deposition method as a
transparent conductive film.
[0160] In the vapor deposition chamber 1811, any known EL materials
(in particular, low-molecule type organic EL materials) can be
formed. Typical examples for the light-emitting layer include
Alg.sub.3 (tris-8-quinolinolato aluminum complex) or DSA (distyl
allylene derivative), while typical examples for the charge
injection layer include CuPc (copper phthalocyanine), LiF (lithium
fluoride), or acacK (potassium acetylacetonate). Furthermore,
typical examples for the charge transport layer include TPD
(triphenylamine derivative) or NPD (anthracene derivative).
[0161] In addition, it is also possible to perform co-vapor
deposition of the above-mentioned EL material and a fluorescent
material (typically, coumarine 6, rubrene, Nile red, DCM,
quinacridon, or the like). As the fluorescent material, any known
materials may be used. Moreover, it is also possible to perform
co-vapor deposition of the EL material and an element belonging to
Group 1 or Group 2 in the periodic table, so that a portion of the
light-emitting layer can exhibit a function as the charge transport
layer or the charge injection layer. The term co-vapor deposition
refers to a vapor deposition method in which a plurality of vapor
deposition sources are simultaneously heated to mix different
materials with each other during the film formation stage.
[0162] In either case, the vapor deposition chamber 1811 is
shielded from the transportation chamber (A) 1801 by means of the
gate 1800f, and the film formation of the EL material or the
conductive film can be performed in vacuum. The film formation is
performed with the face-down orientation.
[0163] Reference numeral 1812 denotes an encapsulation chamber
(also referred to as the sealing chamber or the grove box), that is
coupled to the transportation chamber (A) 1801 via a gate 1800g. In
the encapsulation chamber 1812, a process for finally sealing the
EL element into a closed space is performed. This process is
intended to provide the formed EL element with protection against
oxygen or water. For this purpose, the EL element is mechanically
sealed by means of the cover member. Alternatively, it is also
possible to seal the EL element by means of a thermosetting resin
or a UV-curable resin.
[0164] The cover member is adhered to the substrate with the EL
element formed thereon by means of the thermosetting resin or the
UV-curable resin. The resin is cured through a heat treatment or a
UV irradiation process to form a closed space.
[0165] In the film formation apparatus shown in FIG. 18, a
mechanism 1813 for UV irradiation is provided within the
encapsulation chamber 1812 (such a mechanism is referred to as the
UV irradiation mechanism 1813 hereinafter). Thus, the UV curable
resin is allowed to be cured by UV light emitted from this UV
irradiation mechanism 1813. The inner pressure of the encapsulation
chamber 1812 may be reduced by providing an exhaust pump, or
increased while purging the inner space with a nitrogen gas or an
inert gas having high purity.
[0166] A receiving chamber (path box) 1814 is coupled to the
encapsulation chamber 1812. The receiving chamber 1814 is provided
with a transportation mechanism (C) 1815 for transporting to the
receiving chamber 1814 the substrate for which the encapsulation of
the EL element is completed in the encapsulation chamber 1812. The
inner pressure of the receiving chamber 1814 can be also reduced by
providing an exhaust pump. The receiving chamber 1814 is intended
to prevent the encapsulation chamber 1812 from being directly
exposed to the ambient air, and the substrate is taken out from the
receiving chamber 1814.
[0167] As described in the above, the film formation apparatus
shown in FIG. 18 allows the EL element to be completely sealed into
a closed space without being exposed to the ambient air, and
accordingly, realizes fabrication of a light-emitting device having
a high reliability.
Embodiment 12
[0168] The gate-side driving circuit as shown in FIG. 1 and the
source-side driving circuit as shown in FIG. 3 can be applied, not
only to the light-emitting device, but also to the liquid crystal
display device. An external appearance of the liquid crystal
display device in accordance with the present invention is
illustrated in FIG. 19(A), while FIG. 19(B) illustrates the
cross-sectional structure of its pixel section.
[0169] In FIG. 19(A), a pixel section 1901, a gate-side driver
circuit 1902 and a source-side driver circuit 1903 are formed on a
substrate 1900. In this case, the pixel section as shown in FIG. 5
is used as the pixel section 1901. Moreover, the gate-side driving
circuit shown in FIG. 1 is used as the gate-side driver circuit
1902, while the source-side driving circuit shown in FIG. 3 is used
as the source-side driver circuit 1903.
[0170] A gate wiring 1904 and a source wiring 1905 extend from the
gate-side driver circuit 1902 and the source-side driver circuit
1903, respectively, and a pixel TFT 1906 is formed at the crossing
point of the gate wiring 1904 and the source wiring 1905. To the
pixel TFT 1906, a retaining capacitance 1907 and a liquid crystal
element 1908 are connected in parallel. Furthermore, connecting
wirings 1910 and 1911 are formed to extend from an FPC 1909 to
input terminals of the driver circuits. Reference numeral 1912
denotes a counter substrate.
[0171] In the pixel structure as shown in FIG. 19(B), the p-channel
TFT 1913 forming the driver circuit and the p-channel TFT 1914
serving as the switching element may be fabricated in accordance
with Embodiment 2 described previously. It should be noted that
reference numeral 1915 denotes an orientation film, 1916 denotes a
counter substrate, 1917 denotes a light shielding film, 1918
denotes a counter electrode, 1919 denotes an orientation film, 1920
denotes a sealing member, 1921 denotes a spacer made of a resin,
and 1922 denotes liquid crystal. These components may be formed by
any known method. Furthermore, the structure of the liquid crystal
element is not limited to that described in the present
embodiment.
Embodiment 13
[0172] Although the examples in which the pixel section and the
driver circuit are formed of p-channel TFTs have been described in
Embodiments 1 through 10 and 12, it is also possible to form the
pixel section and the driver, only of n-channel TFTs. In this case,
the driver circuits are required to be slightly modified such that,
for example, the polarities of the power source lines are inverted
in the driver circuits.
[0173] In such a case, the anode and the cathode are replaced with
each other, so that the structure of the EL element is reversed. In
other words, it is preferable to realize a structure in which the
cathode is connected to a drain of the current-controlling TFT. It
should be noted that in Embodiments 8 to 10, all TFTs other than
the switching TFT and the current-controlling TFT, if they exist in
the pixel, are formed as the n-channel TFT.
Embodiment 14
[0174] In the light-emitting device as described in Embodiment 1,
it is preferable to provide a silicon nitride film or a silicon
oxynitride film as the underlying film 502, and to cover the
switching TFT 601 and the current-controlling 602 with the
passivation film 517 including a silicon nitride film or a silicon
oxynitride film.
[0175] In such a structure, the switching TFT 601 and the
current-controlling TFT 602 are sandwiched between the silicon
nitride film or the silicon oxynitride film. Thus, water or movable
ions can be effectively prevented from entering into the device
from the external atmosphere.
[0176] Moreover, it is preferable to provide a silicon nitride film
or a DLC (diamond-like carbon) film between the pixel electrode 523
and a planarization film 518 made of an organic resin formed on the
passivation film 517, and further provide the aforementioned
silicon nitride film or DLC film on the cathode.
[0177] In such a structure, the EL element is sandwiched between
the silicon nitride films or the DLC films. Thus, not only water or
movable ions from the external atmosphere but also oxygen can be
effectively prevented from entering into the device. Although the
organic materials to be used in the light-emitting layer or the
like in the EL element are otherwise likely to be easily oxidized
thereby resulting in deterioration, the structure in the present
embodiment can allow the reliability of the device to be
significantly improved.
[0178] As described in the above, reliability of the entire
light-emitting device can be improved by providing a measure for
protecting the TFTs as well as a measure for protecting the EL
element.
[0179] The structure as described in the present embodiment can be
freely combined with any structures in Embodiments 1 through
10.
Embodiment 15
[0180] The display device formed by implementing the present
invention can be used as a display portion of various kinds of
electric equipments. For instance, when appreciating a television
broadcast or the like, a display incorporating a 20 to 60 inch
diagonal display device of the present invention in a casing may be
used. Note that a personal computer display, a television broadcast
receiving display, and a display for exhibiting all information
such as a display for displaying announcements are included in the
displays having the display device incorporated in a casing.
[0181] The following can be given as other electronic equipments of
the present invention: a video camera; a digital camera; a goggle
type display (head mounted display); a navigation system; an audio
playback device (such as a car audio stereo or an audio component
stereo); a notebook type personal computer; a game apparatus; a
portable information terminal (such as a mobile computer, a
portable telephone, a portable game machine, or an electronic
book); and an image playback device equipped with a recording
medium (specifically, device provided with a display portion which
plays back images in a recording medium and displays the images).
Specific examples of these electronic equipments are shown in FIGS.
20 and 21.
[0182] FIG. 20A shows a display having a display device
incorporated in a casing, and the display contains a casing 2001, a
support stand 2002, a display portion 2003 and the like. The
display device of the present invention can be used as the display
portion 2003.
[0183] FIG. 20B shows a video camera, and contains a main body
2101, a display portion 2102, a sound input portion 2103, operation
switches 2104, a battery 2105, an image receiving portion 2106 and
the like. The display device of the present invention can be used
as the display portion 2102.
[0184] FIG. 20C is a portion (right side) of a head mounted EL
display, and contains a main body 2201, a signal cable 2202, a head
fixing band 2203, a display portion 2204, an optical system 2205, a
light-emitting device 2206 and the like. The present invention can
be applied to the self-emitting device 2206.
[0185] FIG. 20D is an image playback device equipped with a
recording medium (specifically, a DVD playback device), and
contains a main body 2301, a recording medium (such as a DVD) 2302,
operation switches 2303, a display portion (a) 2304, a display
portion (b) 2305 and the like. The display portion (a) 2304 is
mainly used for displaying image information. The display portion
(b) 2305 is mainly used for displaying character information. The
display device of the present invention can be used as the display
portion (a) 2304 and as the display portion (b) 2305. Note that the
image playback device equipped with the recording medium includes
devices such as household game machines.
[0186] FIG. 20E shows a portable (mobile) computer, and contains a
main body 2401, a camera portion 2402, an image receiving portion
2403, operation switches 2404, a display portion 2405 and the like.
The display device of the present invention can be used as the
display portion 2405.
[0187] FIG. 20F is a personal computer, and contains a main body
2501, a casing 2502, a display portion 2503, a keyboard 2504 and
the like. The display device of the present invention can be used
as the display portion 2503.
[0188] FIG. 21A shows a rear type projector (projection TV)
comprising a main body 2601, an optical source 2602, a liquid
crystal display device 2603, a polarization beam splitter 2604,
reflectors 2605 and 2606 and a screen 2607. The present invention
is applicable to the liquid crystal display device 2603.
[0189] FIG. 21B shows a front type projector comprising a main body
2701, an optical source 2702, a liquid crystal display device 2703,
an optical system 2704 and a screen 2705. The present invention is
applicable to the liquid crystal display device 2703.
[0190] Note that, if the luminance further increases in the future,
although not shown, then it will become possible to use the
light-emitting device of the present invention in a front type or a
rear type projector by expanding and projecting light containing
output image information with a lens, an optical fiber or the
like.
[0191] In addition, since the light-emitting device conserves power
in the light-emitting portion, it is preferable to display
information so as to make the light-emitting portion as small as
possible. Consequently, when using the light-emitting device in a
display portion mainly for character information, such as in a
portable information terminal, in particular a portable telephone
or an audio playback device, it is preferable to drive the
light-emitting device so as to form character information by the
light-emitting portions while non-light-emitting portions are set
as background.
[0192] FIG. 21C shows a portable telephone, and contains a main
body 2801, a sound output portion 2802, a sound input portion 2803,
a display portion 2804, operation switches 2805, and an antenna
2806. The light-emitting device of the present invention can be
used as the display portion 2804. Note that by displaying white
color characters in a black color background, the display portion
2804 can suppress the power consumption of the portable telephone.
Of course, it is possible to also use the liquid crystal display
device of the present invention for the display portion 2804.
[0193] FIG. 21D shows an audio playback device, specifically a car
audio stereo, and contains a main body 2901, a display portion
2902, and operation switches 2903 and 2904. The light-emitting
device of the present invention can be used as the display portion
2902. Further, a car audio stereo is shown in this embodiment, but
a portable type or a household audio playback device may also be
used. Note that by displaying white color characters in a black
color background, the display portion 2904 can suppress the power
consumption. This is especially effective in a portable type audio
playback device. Of course, it is possible to also use the liquid
crystal display device of the present invention for the display
portion 2804.
[0194] Thus, the application range of the present invention is
extremely wide, whereby it may be employed in electric equipments
of all fields. Further, the electric equipments of this embodiment
may employ the light-emitting device having any of the
constitutions of Embodiments 1 through 14.
[0195] Thus, in accordance with the present invention, the display
device can be fabricated with very small number of fabrication
steps. Accordingly. a fabrication yield can be increased, while a
fabrication cost can be reduced, thereby resulting in an
inexpensive display device being fabricated.
[0196] Furthermore, since an inexpensive display device can be
provided, various electrical apparatuses which employ the display
device in their display section can be provided at a low price.
* * * * *