U.S. patent application number 15/263428 was filed with the patent office on 2016-12-29 for liquid crystal display device.
The applicant listed for this patent is Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Shingo Eguchi, Etsuko Fujimoto, Yutaka Shionoiri, Shunpei YAMAZAKI.
Application Number | 20160377918 15/263428 |
Document ID | / |
Family ID | 27800058 |
Filed Date | 2016-12-29 |
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United States Patent
Application |
20160377918 |
Kind Code |
A1 |
YAMAZAKI; Shunpei ; et
al. |
December 29, 2016 |
Liquid Crystal Display Device
Abstract
It is an object to provide a display having high visibility and
a transflective type liquid crystal display device having a
reflection electrode having a concavo-convex structure formed
without especially increasing the process. During manufacturing a
transflective liquid crystal display device, a reflection electrode
of a plurality of irregularly arranged island-like patterns and a
transparent electrode of a transparent conductive film are layered
in forming an electrode having transparent and reflection
electrodes thereby having a concavo-convex form to enhance the
scattering ability of light and hence the visibility of display.
Furthermore, because the plurality of irregularly arranged
island-like patterns can be formed simultaneous with an
interconnection, a concavo-convex structure can be formed during
the manufacturing process without especially increasing the
patterning process only for forming a concavo-convex structure. It
is accordingly possible to greatly reduce cost and improve
productivity.
Inventors: |
YAMAZAKI; Shunpei; (Tokyo,
JP) ; Eguchi; Shingo; (Tochigi, JP) ;
Shionoiri; Yutaka; (Isehara, JP) ; Fujimoto;
Etsuko; (Sagarnihara, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Atsugi-shi |
|
JP |
|
|
Family ID: |
27800058 |
Appl. No.: |
15/263428 |
Filed: |
September 13, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11383286 |
May 15, 2006 |
9448432 |
|
|
15263428 |
|
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|
10374999 |
Feb 28, 2003 |
7053969 |
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11383286 |
|
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Current U.S.
Class: |
257/72 |
Current CPC
Class: |
G02F 2201/123 20130101;
G02F 1/13439 20130101; G02F 1/133555 20130101; G02F 1/136227
20130101; H01L 27/1255 20130101; H01L 29/42384 20130101; G02F
1/134309 20130101; G02F 1/1368 20130101 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335; H01L 29/423 20060101 H01L029/423; G02F 1/1343
20060101 G02F001/1343; H01L 27/12 20060101 H01L027/12; G02F 1/1368
20060101 G02F001/1368; G02F 1/1362 20060101 G02F001/1362 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2002 |
JP |
2002-055830 |
Claims
1. (canceled)
2. A semiconductor device comprising: a thin-film transistor formed
over a substrate; an insulating film over the thin-film transistor;
an interconnection and a plurality of island-like conductive films
over the insulating film; and a transparent conductive film over
the interconnection and the plurality of island-like conductive
films.
3. A semiconductor device according to claim 2, wherein the
plurality of island-like conductive films each have a pattern end
having a taper angle of 5-60 degrees.
4. A semiconductor device according to claim 2, wherein the
plurality of island-like conductive films have an area ratio of
50-90% of an area occupied by the transparent conductive film.
5. A semiconductor device according to claim 2, wherein the
semiconductor device is incorporated into an electronic apparatus
selected from the group consisting of a digital still camera, a
notebook personal computer, a mobile computer, a portable type
image reproducing apparatus having a recording medium, a video
camera and a cellular phone.
6. A semiconductor device according to claim 2, wherein the
transparent conductive film is a pixel electrode.
7. A semiconductor device according to claim 2, wherein the
plurality of island-like conductive films are irregularly
arranged.
8. A semiconductor device comprising: a thin-film transistor formed
over a substrate; an insulating film over the thin-film transistor;
an interconnection and a plurality of island-like conductive films
over the insulating film; and a transparent conductive film over
the interconnection and the plurality of island-like conductive
films, wherein the thin-film transistor and the transparent
conductive film are electrically connected via the
interconnection.
9. A semiconductor device according to claim 8, wherein the
plurality of island-like conductive films each have a pattern end
having a taper angle of 5-60 degrees.
10. A semiconductor device according to claim 8, wherein the
plurality of island-like conductive films have an area ratio of
50-90% of an area occupied by the transparent conductive film.
11. A semiconductor device according to claim 8, wherein the
semiconductor device is incorporated into an electronic apparatus
selected from the group consisting of a digital still camera, a
notebook personal computer, a mobile computer, a portable type
image reproducing apparatus having a recording medium, a video
camera and a cellular phone.
12. A semiconductor device according to claim 8, wherein the
transparent conductive film is a pixel electrode.
13. A semiconductor device according to claim 8, wherein the
plurality of island-like conductive films are irregularly
arranged.
14. A semiconductor device comprising: a thin-film transistor
formed over a substrate; an insulating film over the thin-film
transistor; an interconnection and a plurality of island-like
conductive films over the insulating film; and a transparent
conductive film over the interconnection and the plurality of
island-like conductive films, wherein the thin-film transistor and
the transparent conductive film are electrically connected via the
interconnection, and wherein the interconnection is formed from a
same layer as the plurality of island-like conductive films.
15. A semiconductor device according to claim 14, wherein the
plurality of island-like conductive films each have a pattern end
having a taper angle of 5-60 degrees.
16. A semiconductor device according to claim 14, wherein the
plurality of island-like conductive films have an area ratio of
50-90% of an area occupied by the transparent conductive film.
17. A semiconductor device according to claim 14, wherein the
semiconductor device is incorporated into an electronic apparatus
selected from the group consisting of a digital still camera, a
notebook personal computer, a mobile computer, a portable type
image reproducing apparatus having a recording medium, a video
camera and a cellular phone.
18. A semiconductor device according to claim 14, wherein the
transparent conductive film is a pixel electrode.
19. A semiconductor device according to claim 14, wherein the
plurality of island-like conductive films are irregularly arranged.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/383,286, filed May 15, 2006, now allowed, which is a
division of U.S. application Ser. No. 10/374,999, filed Feb. 28,
2003, now U.S. Pat. No. 7,053,969, which claims the benefit of a
foreign priority application filed in Japan as Serial No.
2002-055830 on Mar. 1, 2002, all of which are incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a liquid crystal display
device of a passive matrix type and an active matrix type.
Particularly, the invention relates to an electrode structure of a
transflective type liquid crystal display device having both
functions of a transmission type and a reflection type.
[0004] 2. Description of the Related Art
[0005] In recent years, by explosive spread of a portable
information terminal represented by a cellular phone, there is
needed a display capable of dealing with light-weighted formation,
low power consumption and a change in an environment of use.
[0006] Further, in views of thin film formation and light-weighted
formation, a liquid crystal display device or an organic EL display
device is representatively promising.
[0007] Power consumption of a transmission type display device is
inconsiderable for driving only a display. However, a liquid
crystal per se does not emit light and therefore, a back light is
needed for displaying as a display. For use of a cellular phone, an
EL back light is generally used, however, power is additionally
needed for the back light and a specific characteristic of low
power consumption of a liquid crystal is not fully utilized, which
are disadvantageous in low power consumption. Further, although in
a dark environment, display of a display is viewed with excellent
contrast, in an ordinary bright environment, the display is not
viewed so well and there is a drawback in adaptability in
accordance with the environment of use both in cases of an upper
emitting type and a lower emitting type.
[0008] Further, the organic EL display device is characterized in
which a display element per se emits light. Although power
consumption thereof becomes larger than that of a reflection type
liquid crystal display device, the power consumption is smaller
than that of a transmission type liquid crystal display device
(having back light). However, similar to the case of the
transmission type liquid crystal display device, although in a dark
environment, display of a display is viewed excellently, in an
ordinary bright environment, the display is not viewed so well and
therefore, there is still a drawback in adaptability in accordance
with an environment of use both in cases of the upper emitting type
and the lower emitting type.
[0009] Further, the reflection type liquid crystal display device
utilizes outside light from an environment as light for display. On
the side of the display, the back light is not basically needed,
only power for driving a liquid crystal and a drive circuit is
needed and therefore, positive low power consumption is achieved.
Further, quite contrary to the former two, although in a bright
environment, display of a display is viewed excellently, in a dark
environment, the display is not viewed so well. Considering the use
of a portable information terminal, the portable information
terminal is mainly used outdoors and there is frequently a case of
viewing the display in a comparatively bright environment, however,
this is still insufficient in terms of adaptability in accordance
with an environment of use. Therefore, locally, a reflection type
display device integrated with a front light is on sale such that
the display can be carried out even in a dark environment.
[0010] Hence, attention is given to a transflective type liquid
crystal display having advantages of both of a transmission type
and a reflection type liquid crystal display device by combining
the device. In a bright environment, a characteristic of the
reflection type of low power consumption and excellence in
visibility under the environment is utilized, meanwhile, in a dark
environment, a characteristic of excellence in contrast provided to
the transmission type is utilized by using a back light.
[0011] A transflective type liquid crystal display device is
disclosed in JP-A-11-101992. The device is a reflection and
transmission type (transflective type) liquid crystal display
device. More concretely, by fabricating a reflection portion for
reflecting outside light and a transmission portion for
transmitting light from a back light in a single display pixel, in
a case where the surrounding is totally dark, as a reflection and
transmission type liquid crystal display device, the display is
carried out by utilizing light transmitting through the
transmission portion from the back light and light reflected by the
reflection portion formed by a film having comparatively high
reflectance, while in a case where the surrounding is bright, as a
reflection type liquid crystal display device, the display is
carried out by utilizing light reflected by the reflection portion
formed by the film having the comparatively high optical
reflectance.
[0012] Further, in the above-described transflective type liquid
crystal display device, particularly at the reflection portion for
carrying out reflection display, a special concavo-convex structure
having optical diffusion is given. Since a reflection electrode,
according to the structure thereof, reflects light from a certain
direction by a certain incident angle only to a location having a
specific exit angle in a specific direction (Snell's law) to the
surface, when the surface is flat, a direction and an angle of
emitting light are determined to be constant relative to incidence
of light. If a display is fabricated under such a state, a display
having very poor visibility is brought about.
[0013] The liquid crystal display device of a transflective type is
considered as a display well coped with the particular service
conditions for the personal digital assistant. Particularly, in the
cellular phone application, huge demand is to be prospectively
expected from now on. For this reason, in order to secure stable
demand or cope with huge demand, there is an apparent need to make
efforts toward the further reduction of cost.
[0014] However, in order to form a concavo-convex structure as
noted before, there is a need for a method to provide a
concavo-convex form in the layer lower than the reflection
electrode and then form thereon a reflection electrode.
[0015] Meanwhile, in order to fabricate a transflective type liquid
crystal display device without limited to the foregoing example,
patterning is required for forming a concavo-convex structure in
one or both surfaces of a reflection electrode and a transparent
electrode configuring a pixel electrode or in the layer beneath the
pixel electrode, thus increasing the processes. The increase of
processes would incur a disadvantageous situation, including yield
reduction, prolonged process time and increasing cost.
[0016] Accordingly, it is an object of the present invention to
provide a display having high visibility and a transflective type
liquid crystal display device having a reflection electrode with a
concavo-convex structure formed without particularly increasing the
processes.
SUMMARY OF THE INVENTION
[0017] In order to solve the foregoing problem, the present
invention is characterized in that, in manufacturing a
transflective liquid crystal display device, a reflection electrode
of a plurality of irregularly arranged island-like patterns and a
transparent electrode of transparent conductive film are layered in
forming an electrode having transparent and reflection electrodes
thereby providing a concavo-convex form and enhancing the
scattering ability of light and hence display visibility.
Furthermore, because the plurality of irregularly arranged
island-like patterns can be formed simultaneous with the
interconnection, a concavo-convex structure can be formed in the
manufacturing process without especially increasing the patterning
process only for forming a concavo-convex structure. Accordingly,
it is possible to greatly reduce cost and improve productivity.
[0018] A liquid crystal display device of the invention is a liquid
crystal display device comprising: a transparent conductive film
formed on an insulating surface; and an interconnection and a
plurality of irregularly arranged island-like patterns that are
formed on the transparent conductive film; electrical connection
being made between the transparent conductive film, the
interconnection and the plurality of irregularly arranged
island-like patterns.
[0019] The plurality of irregularly arranged island-like patterns
serve as a reflection electrode. Also, by layering the transparent
electrode of transparent conductive film and the reflection
electrode of the plurality of irregularly arranged island-like
patterns, the region having the reflection electrode serves as an
electrode having a reflectivity to light. The region, not having a
reflection electrode on the transparent electrode but exposed with
the transparent electrode in the surface, serves as a transparent
electrode having transmittability to light. Accordingly, in the
invention, a transflective type liquid crystal display device is
formed which has, as a pixel electrode, an electrode having two
kinds of natures, i.e. reflectivity and transmittability. Namely,
the pixel electrode of the invention comprises a reflection
electrode and a transparent electrode, thus having a concavo-convex
structure.
[0020] Meanwhile, the reflective conductive film of the invention
assumably use a conductive film having a reflectivity of 75% or
higher in respect of the vertical reflection characteristic in a
wavelength of 400-800 nm (visible light region). Incidentally, such
a material can use aluminum (Al) or silver (Ag), or, besides them,
an alloy material based on these.
[0021] Also, a liquid crystal display device in another structure
of the invention is a liquid crystal display device comprising: a
thin-film transistor formed over a substrate; a transparent
conductive film formed on the thin-film transistor through an
insulating film; and an interconnection and a plurality of
irregularly arranged island-like patterns that are formed on the
transparent conductive film; the interconnection electrically
connecting between the thin-film transistor and the transparent
conductive film.
[0022] Furthermore, a liquid crystal display device of the
invention is a liquid crystal display device characterized by:
having a first substrate having a first transparent conductive
film, an interconnection and a plurality of irregularly arranged
island-like patterns, a second substrate having a second
transparent conductive film and a liquid crystal; the
interconnection and the plurality of irregularly arranged
island-like patterns being formed on the first transparent
conductive film; electrical connection being made between the
transparent conductive film, the interconnection and the plurality
of irregularly arranged island-like patterns; a film forming
surface of the first substrate and a film forming surface of the
second substrate being arranged opposite to each other, and the
liquid crystal being sandwiched between the first substrate and the
second substrate.
[0023] Furthermore, a liquid crystal display device of the
invention is a liquid crystal display device characterized by:
having a first substrate having a thin-film transistor, a first
transparent conductive film, an interconnection and a plurality of
irregularly arranged island-like patterns, a second substrate
having a second transparent conductive film and a liquid crystal;
the interconnection and the plurality of irregularly arranged
island-like patterns being formed on the first transparent
conductive film; the interconnection electrically connecting the
thin-film transistor, the first transparent conductive film and the
plurality of irregularly arranged island-like patterns; a film
forming surface of the first substrate and a film forming surface
of the second substrate being arranged opposite to each other, and
the liquid crystal being sandwiched between the first substrate and
the second substrate.
[0024] Incidentally, according to each of the above structures, it
is possible to form, by etching, the plurality of irregularly
arranged island-like patterns of a reflective conductive film and
the interconnection. Furthermore, in the case of simultaneously
forming them by etching, because a concavo-convex structure can be
configured as viewed at a film-forming surface of the reflective
conductive film, it is possible to reduce the photolithography
process used in usually forming a concavo-convex structure. This
can realize great cost reduction and improvement in
productivity.
[0025] Meanwhile, the plurality of irregularly arranged island-like
patterns to be formed in each of the above structures are formed
and arranged in a random form, and electrically connected to the
first transparent conductive film. However, the island-like pattern
formed by etching the reflective conductive film is desirably given
a smaller taper angle at a pattern end in view of improving the
ability of reflection. Incidentally, the plurality of island-like
patterns of the invention is characterized by a taper angle of 5-60
degrees at each pattern end.
[0026] Furthermore, in each of the above structures, the plurality
of island-like patterns of reflective conductive film formed in the
pixel region is characterized to have a occupation area ratio of
50-90% of the area of the pixel region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a view explaining a device structure of a liquid
crystal display device of the present invention;
[0028] FIGS. 2A to 2D are views explaining a structure of a
reflection electrode of the invention;
[0029] FIGS. 3A to 3D are views showing a manufacturing process for
a liquid crystal display device of the invention;
[0030] FIG. 4 is a view showing the manufacturing process for a
liquid crystal display device of the invention;
[0031] FIG. 5 is a view showing the manufacturing process for a
liquid crystal display device of the invention;
[0032] FIG. 6 is a view showing the manufacturing process for a
liquid crystal display device of the invention;
[0033] FIG. 7 is a view showing the manufacturing process for a
liquid crystal display device of the invention;
[0034] FIGS. 8A to 8D are views showing the manufacturing process
for a liquid crystal display device of the invention;
[0035] FIG. 9 is a view showing the manufacturing process for a
liquid crystal display device of the invention;
[0036] FIG. 10 is a view showing the manufacturing process for a
liquid crystal display device of the invention;
[0037] FIG. 11 is a view explaining a structure of a liquid crystal
display device of the invention;
[0038] FIG. 12 is a view explaining a device structure of the
liquid crystal display device of the invention;
[0039] FIG. 13 is a diagram explaining a circuit configuration
usable in the invention;
[0040] FIG. 14 is a diagram explaining a circuit configuration
usable in the invention;
[0041] FIG. 15 is a view explaining an exterior appearance of the
liquid crystal display device of the invention; and
[0042] FIGS. 16A to 16F are views showing an example of electrical
apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] An embodiment of the present invention will now be explained
with reference to FIG. 1. A semiconductor layer 105 is formed over
a substrate 101. The semiconductor layer 105 is formed, of
polycrystal semiconductor that an amorphous semiconductor has been
crystallized by a thermal process, having a thickness of
approximately 30-750 nm, on which a gate insulating film 106 is
formed furthermore. The gate insulating film 106 is formed of
silicon oxide having 30-100 nm. Also, although the polycrystal
semiconductor is used as the semiconductor layer 105, an amorphous
semiconductor also can be used as the semiconductor layer 105.
[0044] A gate electrode 107 and a capacitance interconnection 108
are formed in a same layer on the gate insulating film 106, on
which a first insulating film 109 of silicon oxide and a second
insulating film 110 of acryl are formed. The material for forming a
first insulating film 109 can use, besides silicon oxide, a
silicon-contained inorganic material, such as silicon nitride,
silicon nitride oxide or applied silicon oxide (SOG: Spin On
Glass). The material for forming a second insulating film 110 can
use, besides acryl (including photosensitive acryl), an organic
material, such as polyimide, polyamide, BCB
(benzocyclo-butene).
[0045] A transparent electrode 111 is an electrode for allowing
incident light to transmit toward the substrate 101. The
transparent electrode 111 is formed in a film thickness of 100-200
nm by using, as a material, a transparent conductive film of indium
oxide-tin (ITO) or indium oxide mixed with zinc oxide (ZnO) in
2-20[%]. This is further patterned to form transparent electrodes
111 on a pixel-by-pixel basis.
[0046] An interconnection 112 is an electrode forming a contact to
a source region 102 of a TFT 115, also serving as a source line.
The interconnection 113 is an electrode forming a contact to a
drain region of the TFT 115.
[0047] The semiconductor layer 105 is formed with a source region
102, a drain region 103 and a channel region 104. Except the source
region 102 and drain region 103, the semiconductor layer 105 formed
in a region overlapped with a capacitance interconnection 108
serves as one electrode of a capacitance element.
[0048] Meanwhile, on the transparent electrode 111 formed before, a
reflection electrode 114 is formed by a reflection conductive film
in the same film as the conductive film forming the
interconnections 112, 113. Namely, a photolithography technique is
used to form a plurality of island-like patterns on the transparent
electrode 111 in the pixel region. In the region other than those,
interconnections 112, 113 are formed. The island-like patterns
herein are in a random form and arrangement forming the reflecting
electrode 114. The reflection electrode 114 thus structured can
possess a function to scatter the incident light on the
surface.
[0049] According to the structure of the invention, the light,
incident on the reflection electrode 114 formed on the transparent
electrode 111, is cause to scatter by the form of the reflection
electrode 114. However, the light incident on a region, exposed
with the transparent electrode 222 instead of forming the
reflection electrode 114, transmits through the transparent
electrode 111 and exits toward the substrate 101.
[0050] The reflection electrode formed in the invention, formed in
a random form and region as shown in its form in FIG. 2A, can cause
deviation between the angle of an incident light on the reflection
electrode (incident angle) and the angle of a light reflected upon
the reflection electrode (reflection angle) thereby scattering the
light.
[0051] Incidentally, in the invention, importance is placed on the
form of a plurality of reflectors configuring the reflection
electrode in respect of causing deviation between the incident
angle and the reflection angle, i.e. an angle representative of in
what degree the taper slope surface (reflection surface) 210 of
each reflector shown in FIG. 2B inclines with respect to a
substrate surface (reference surface) 211. This is shown as a taper
angle (.theta.) 212.
[0052] In this embodiment, the reflectors are formed with a taper
angle (.theta.) 212 of 5-60 degrees. Due to this, the exit angle
with respect to the taper slope surface (reflection surface) 211 is
deviated as compared to the exit angle with respect to the
substrate surface (reference surface) 210 to cause light
scattering. This makes it possible to improve visibility.
[0053] FIG. 2C shows a behavior of incident light 213 and
reflection light 214 upon a reflection surface not sloped. It is
assumed that an incident direction on the reference surface 211 is
a.sub.in, an exit direction is a.sub.out, an incident direction on
the reflection surface 210 is a'.sub.in, and an exit direction is
a'.sub.out. Furthermore, an incident angle (.phi..sub.1) 215 and an
exit angle (.phi..sub.2) 216 are defined with respect to the
reference surface. Herein, since there is coincidence between the
reference surface 211 and the reflection surface 210,
a.sub.in=a'.sub.in=.phi..sub.1 and a.sub.out=a'.sub.out=.phi..sub.2
are held.
[0054] Also, from a'.sub.in=a'.sub.out held on the Snell's law,
a.sub.in=a.sub.out and .phi..sub.1=.phi..sub.2 are held.
[0055] On the other hand, FIG. 2D shows a behavior of incident
light 213 and exit light 214 in the case the taper slope surface
having a taper angle (.theta.) 212 is made as a reflection
surface.
[0056] Provided that the incident light 213 and the exit light 214
are respectively an incident angle (.phi..sub.1') 217 and an exit
angle (.phi..sub.2') 218 with respect to the reference surface 211,
then a.sub.in=.phi..sub.1' and a.sub.out=.phi..sub.2' and further
a'.sub.in=.phi..sub.1'+.theta. and a'.sub.out=.phi..sub.2'-.theta.
are held.
[0057] Meanwhile, because a'.sub.in=a'.sub.out is held on the
Snell's law, .phi..sub.1'+.theta.=.phi..sub.2'-.theta. is held.
From this equation, the relationship between an incident angle
(.phi..sub.1') 217 and an exit angle (.phi..sub.2') 218 can be
expressed by .phi..sub.2'-.phi..sub.1'=2.theta.. This means that
there is a deviation by 2.theta. between the incident direction
(a.sub.in) of incident light 213 and the exit direction (a.sub.out)
of exit light 214.
[0058] In order to fabricate a panel further excellent in
visibility, it is preferred to evenly distribute the relevant
deviation angle (2.theta.) within a range of 40 degrees or smaller.
Consequently, the reflectors 204 are further, preferably formed to
provide a taper angle (.theta.) 212 of 20 degrees or smaller.
[0059] In this embodiment, by forming the reflectors 204
structuring a reflection electrode 114 with a taper angle (.theta.)
212 of 5-60 degrees, the light incident on the reflection electrode
114 can be scattered efficiently. Accordingly, the structure of the
invention makes it possible to enhance display visibility without
increasing the manufacture processes for TFTs.
[0060] Incidentally, a transflective type liquid crystal display
device can be formed by mating a counter substrate (not shown)
having a counter electrode on a device substrate (FIG. 1) having
TFTs on the substrate explained in the embodiment and then
providing a liquid crystal between the both.
EXAMPLES
[0061] Examples of the invention will be explained as follows.
Example 1
[0062] According to the example, an example of steps of fabricating
an active matrix substrate having a top gate type TFT will be
shown. Further, FIG. 3A through FIG. 7 showing top views and
sectional views of a portion of a pixel portion will be used for
explanation.
[0063] First, an amorphous semiconductor layer is formed over a
substrate 301 having an insulating surface. Here, a quartz
substrate is used as the substrate 301 and the amorphous
semiconductor layer is formed with a thickness of 10 through 100
nm.
[0064] Further, a glass substrate or a plastic substrate can be
used other than the quartz substrate. When the glass substrate is
used, the glass substrate may be subjected to a heat treatment
previously at a temperature lower than a glass strain point by
about 10 through 20.degree. C. Further, a base film comprising an
insulating film such as a silicon oxide film, a silicon nitride
film, a silicon oxynitride film and the like may be formed on a
surface of the substrate 301 for forming TFT to prevent an impurity
from diffusing from the substrate 301.
[0065] As the amorphous semiconductor layer, an amorphous silicon
film (amorphous silicon film) having a film thickness of 60 nm is
formed by LPCVD method. Successively, the amorphous semiconductor
layer is crystallized. Here, the amorphous semiconductor layer is
crystallized by using a technology described in JP-A-8-78329.
According to the technology described in the publication, an
amorphous silicon film is selectively added with a metal element to
help the crystallization of the amorphous silicon film and a
heating treatment is carried out to thereby form a crystalline
silicon film spreading with an addition region as a start point.
Here, nickel is used as a metal element for helping the
crystallization and after a heat treatment for dehydrogenation
(450.degree. C., 1 hour), a heat treatment for crystallization
(600.degree. C., 12 hours) is carried out. Further, although the
technology described in the publication is used here for the
crystallization, the invention is not particularly limited to the
technology but a publicly known crystallizing processing (laser
crystallizing method, thermal crystallizing method) can be
used.
[0066] Further, as necessary, a laser beam (XeCl: wavelength 308
nm) is irradiated in order to increase a crystallization rate and
repairing a defect that remains in a crystal grain. As the laser
beam, an excimer laser beam, or a second harmonic or third harmonic
of YAG laser having a wavelength equal to or smaller than 400 nm is
used. At any rate, a pulse laser beam having a repeating frequency
of about 10 through 1000 Hz may be used and the laser beam may be
focused to 100 through 400 mJ/cm.sup.2 by an optical system,
irradiated by 90 through 95% of an overlap rate and scanned on a
surface of a silicon film.
[0067] Successively, Ni is gettered from a region constituting an
active layer of TFT. Here, as a gettering method, an example of
using a semiconductor layer including a rare gas element will be
shown. In addition to an oxide film formed by irradiating the laser
beam, a barrier layer comprising an oxide film of a total of 1
through 5 nm is formed by processing a surface for 120 seconds by
ozone water. Successively, an amorphous silicon film including
argon element constituting a gettering site is formed on the
barrier layer by a sputtering method with a film thickness of 150
nm. According to film forming conditions by the sputtering method
of the example, film forming pressure is set to 0.3 Pa, a flow rate
of gas (Ar) is set to 50 (sccm), film forming power is set to 3 kW
and substrate temperature is set to 150.degree. C. Further, atomic
concentration of argon element included in the amorphous silicon
film falls in a range of 3.times.10.sup.20/cm.sup.3 through
6.times.10.sup.20/cm.sup.3 and atomic concentration of oxygen falls
in a range of 1.times.10.sup.19/cm.sup.3 through
3.times.10.sup.19/cm.sup.3 under the above-described conditions.
Thereafter, gettering is carried out by a heat treatment at
650.degree. C. for 3 minutes by using a lamp annealing device.
Further, an electric furnace may be used in place of the lamp
annealing device.
[0068] Successively, by constituting an etching stopper by the
barrier layer, the amorphous silicon film including argon element
constituting the gettering side is selectively removed and
thereafter, the barrier layer is selectively removed by diluted
hydrofluoric acid. Further, in gettering, since nickel tends to
move to a region having a high oxygen concentration, a barrier
layer comprising an oxide film may preferably be removed after
gettering.
[0069] After forming a thin oxide film on a surface of a silicon
film (also referred to as polysilicon film) having the provided
crystalline structure by ozone water, a mask comprising a resist is
formed, the silicon film is etched to a desired shape and a
semiconductor layer 305 separated in an island-like shape is
formed. After forming the semiconductor layer 305, the mask
comprising the resist is removed, a gate insulating film 306
covering the semiconductor layer 305 is formed with a film
thickness of 100 nm and thereafter, thermal oxidation is carried
out.
[0070] Successively, a channel doping step of adding a P-type or an
N-type impurity element to a region for constituting a channel
region of TFT at a low concentration is carried out over an entire
face thereof or selectively. The channel doping step is a step of
controlling threshold voltage of TFT. Further, as an impurity
element for providing P-type to a semiconductor, elements of 13-th
group of the periodic law such as boron (B), aluminum (Al) or
gallium (Ga) are known. Further, as impurity elements for providing
n-type to a semiconductor, elements belonging to 15-th group of the
periodic law, typically, phosphor (P) and arsenic (As) are known.
Further, here, boron is added by a plasma-exciting ion doping
method without subjecting dibolane (B.sub.2H.sub.6) to mass
separation. Naturally, an ion implantation method for carrying out
mass separation may be used.
[0071] Successively, a first conductive film is formed and
patterned to thereby form a gate electrode 307 and a capacitance
interconnection 308. A laminated structure of tantalum nitride
(TaN) (film thickness 30 nm) and tungsten (film thickness 370 nm)
is used. Here, a double gate structure is constituted in the
example. Further, holding capacitance is constituted by the
capacitance interconnection 308 and a region a (303a) constituting
a portion of the semiconductor layer 305 with the gate insulating
film 306 being as a dielectric.
[0072] Then, phosphorus is added at low concentration through the
gate electrode 307 and capacitance interconnection 308 as a mask in
a self-aligned manner. In the region added at low concentration,
phosphorus concentration is controlled to
1.times.10.sup.16-5.times.10.sup.18/cm.sup.3, typically
3.times.10.sup.17-3.times.10.sup.18/cm.sup.3.
[0073] Next, a mask (not shown) is formed to add phosphorus at high
concentration to form a high-concentration impurity region to be
made into a source region 302 or drain region 303. In this
high-concentration impurity region, phosphorus concentration is
controlled to 1.times.10.sup.20-1.times.10.sup.21/cm.sup.3
(typically 2.times.10.sup.20-5.times.10.sup.20/cm.sup.3). The
semiconductor layer 305, in a region overlapped with the gate
electrode 307, is formed into a channel region 304. The region
covered by the mask is formed into a low-concentration impurity
region and into an LDD region 311. Furthermore, a region not
covered by any of the gate electrode 307, the capacitance line 308
and the mask is made as a high-concentration impurity region
including a source region 302 and a drain region 303.
[0074] Further, according to the example, TFTs of the pixel portion
and TFTs of a drive circuit are formed on the same substrate and in
the TFTs of the drive circuit, a low concentration impurity region
having an impurity concentration lower than those of source and
drain regions may be provided between a source and a drain region
on both sides of a channel formation region or the low
concentration impurity region may be provided on one side thereof.
However, it is not always necessarily to provide the low
concentration impurity region on the both sides, a person carrying
out the example may design a mask appropriately.
[0075] In addition, although not illustrated here, because this
example forms p-channel TFTs to be used for a drive circuit formed
on the same substrate as the pixels, the region to be formed into
n-channel TFTs is covered by a mask to add boron thereby forming a
source or drain region.
[0076] Then, after removing the mask, a first insulating film 309
is formed covering the gate electrode 307, the capacitance
interconnection 308. Herein, a silicon oxide film is formed in a
film thickness of 50 nm, and a thermal process is carried out to
activate the n-type or p-type impurity element added at respective
concentrations in the semiconductor layer 305. Herein, thermal
process is made at 850.degree. C. for 30 minutes (FIG. 3A).
Incidentally, a pixel top view herein is shown in FIG. 4. In FIG.
4, the sectional view taken along the dotted line A-A' corresponds
to FIG. 3A.
[0077] Then, after carrying out a hydrogenation process, a second
insulating film 313 is formed of an organic resin material. By
herein using an acryl film having a film thickness of 1 .mu.m, the
second insulating film 313 can be flattened in its surface. This
prevents the affection of a step caused by the pattern formed in
the layer beneath the second insulating film 313. Then, a mask is
formed on the second insulating film 313, to form by etching a
contact hole 312 reaching the semiconductor layer 305 (FIG. 3B).
After forming the contact hole 312, the mask is removed away.
Further, FIG. 5 shows a top view of the pixel in this case. In FIG.
5, a sectional view taken along the dotted line A-A' corresponds to
FIG. 3B.
[0078] Next, a 120-nm transparent conductive film (herein, indium
oxide-tin (ITO) film) is deposited by sputtering, and patterned
into a rectangular form by the use of a photolithography technique.
After carrying out a wet-etching treatment, a heating treatment is
made in a clean oven at 250.degree. C. for 60 minutes thereby
forming a transparent electrode 313 (FIG. 3C). The pixel top view
herein is shown in FIG. 6. In FIG. 6, the sectional view taken
along the dotted line A-A' corresponds to FIG. 3C.
[0079] Next, a second conductive film is formed and patterned. Due
to this, formed are, besides a reflection electrode 314 formed on
the transparent electrode 313, an interconnection 315 which is also
a source line and an intersection 316 electrically connecting
between a TFT 310 and the transparent electrode 313 are formed.
Note that the second conductive film formed herein is a reflective
conductive film to form a reflection electrode of the invention,
which can use aluminum or silver, or otherwise an alloy material
based on these.
[0080] This example uses a layered film having a two-layer
structure continuously formed, by a sputter method, with a Ti film
having 50 nm as the second conductive film and an Si-contained
aluminum film having 500 nm.
[0081] The method of patterning uses a photolithography technique
to form a reflection electrode 314 comprising a plurality of
island-like patterns and interconnections 315, 316. The method for
etching herein uses a dry etching scheme to carry out taper etching
and anisotropic etching.
[0082] At first, a resist mask is formed to carry out a first
etching process for taper etching. The first etching process is
under first and second etching conditions. For etching, an ICP
(Inductively Coupled Plasma) etching technique is suitably used.
Using the ICP etching technique, the film can be etched to a
desired taper form by properly controlling the etching condition
(amount of power applied to a coil-formed electrode, amount of
power applied to a substrate-sided electrode, electrode temperature
close to the substrate, etc.). The etching gas can suitably use a
chlorine-based gas represented by Cl.sub.2, BCl.sub.3, SiCl.sub.4,
CCl.sub.4 or the like, a fluorine-based gas represented by
CF.sub.4, SF.sub.6, NF.sub.3 or the like, or O.sub.2.
[0083] This example uses the ICP (Inductively Coupled Plasma)
etching technique, as a first etching condition, wherein BCl.sub.3,
Cl.sub.2 and O.sub.2 are used for an etching gas. Etching is
conducted with plasma caused by feeding a 500 W RF (13.56 MHz)
power to a coil-formed electrode at a flow rate ratio of these
gasses of 65/10/5 (sccm) under a pressure of 1.2 Pa. A 300 W RF
(13.56 MHz) power is fed also to the substrate side (sample stage)
to apply substantially a negative self-bias voltage. Under the
first etching condition, the Si-contained aluminum film is etched
to make the first conductive layer at its end into a taper
form.
[0084] Thereafter, the second etching condition is changed without
removing the mask. Using CF.sub.4, Cl.sub.2 and O.sub.2 for an
etching gas, etching is conducted for nearly 30 seconds with plasma
caused by feeding a 500 W RF (13.56 MHz) power, to the coil-formed
electrode at a flow rate ratio of these gasses of 25/25/10 (sccm)
under a pressure of 1 Pa. A 20 W RF (13.56 MHz) power is fed also
to the substrate side (sample stage) to apply substantially a
negative self-bias voltage. Under the second etching condition
having CF.sub.4 and Cl.sub.2 mixed together, the Si-contained
aluminum film and the Ti film are both etched in the same
degree.
[0085] In this manner, by the first etching process, the second
conductive film comprising the first and second conductive layers
can be made into a taper form.
[0086] Then, a second etching process for anisotropic etching is
carried out without removing the resist mask. Using herein
BCl.sub.3 and Cl.sub.2 for an etching gas, etching is conducted
with plasma caused by feeding a 300 W RF (13.56 MHz) power to the
coil-formed electrode at a flow rate ratio of these gasses of 80/20
(sccm) under a pressure of 1 Pa. A 50 W RF (13.56 MHz) power is fed
also to the substrate side (sample stage) to apply substantially a
negative self-bias voltage.
[0087] By the above, at a time that a reflection electrode 314 and
interconnections 315 and 316 are formed, the resist is removed to
obtain a structure shown in FIG. 3D. Incidentally, a pixel top view
herein is shown in FIG. 7. In FIG. 7, the sectional view taken
along the dotted line A-A' corresponds to FIG. 3D.
[0088] Further, by randomly forming the reflecting electrode 314
above the transparent electrode 313 as shown in FIG. 7, at portions
of the transparent electrode 313 and the reflecting electrode 314
formed to overlap, light is reflected by the reflecting electrode
314 and at a portion at which the reflecting electrode 314 is not
formed and the transparent electrode 313 is exposed to the surface,
light transmits through an inner portion of the transparent
electrode 313 and is emitted to a side of the substrate 301.
[0089] In this way, the pixel portion having the n-channel type TFT
having the double gate structure and the holding capacitance and
the drive circuit having the n-channel type TFT and the p-channel
type TFT can be formed on the same substrate. In the specification,
such a substrate is referred to as an active matrix substrate for
convenience.
[0090] Further, the example is only an example, needless to say the
invention is not limited to steps of the example. For example, as
respective conductive films, a film of an element selected from the
group constituting of tantalum (Ta), titanium (Ti), molybdenum
(Mo), tungsten (W), chromium (Cr) and silicon (Si) or an alloy
combined with the elements (representatively, Mo--W alloy, Mo--Ta
alloy) can be used. Further, as the respective insulating films, a
silicon oxide film, a silicon nitride film, a silicon oxynitride
film, a film of an organic resin material (polyimide, acrylic
resin, polyamide, polyimideamide, BCB (benzocyclobutene) etc) can
be used.
[0091] Meanwhile, according to the process shown in this example,
it is possible to simultaneously form a reflection electrode 314
and interconnections 315 and 316 by using a interconnection pattern
mask as shown in FIG. 3D. Consequently, the reflection electrode
can be formed separately in plurality in an island form on a
transparent electrode without increasing the number of photo-masks
required in fabricating an active matrix substrate. As a result, in
the manufacture of a transflective type liquid crystal display
device, the process can be shortened thereby giving contribution to
manufacture cost reduction and yield improvement.
Example 2
[0092] This example concretely explains a method for manufacturing
a transflective type liquid crystal display device different in
structure from Example 1.
[0093] At first, an amorphous semiconductor film is formed over a
substrate 801 as shown in FIG. 8A. After crystallizing this, a
semiconductor layer 805 is formed which is separated in an island
form by patterning. Furthermore, on the semiconductor layer 805, a
gate insulating film 806 is formed by an insulating film.
Incidentally, the manufacturing method of up to forming a gate
insulating film 806 is similar to that shown in Example 1, and
hence reference may be made to Example 1. Similarly, after forming
an insulating film covering the semiconductor layer 805, thermal
oxidation is carried out to form a gate insulating film 806.
[0094] Then, a channel dope process is carried out over the entire
surface or selectively, to add a p-type or n-type impurity element
at low concentration to a region to be made into a TFT channel
region.
[0095] A conductive film is formed on the gate insulating film 806.
By patterning this, an interconnection 809 can be formed that is to
be made into a gate electrode 807, a capacitance interconnection
808 and a source line. Incidentally, the first conductive film in
this example is formed by layering TaN (tantalum nitride) formed in
a thickness of 50-100 nm and W (tungsten) formed in a thickness of
100-400 nm.
[0096] Although this example formed the conductive film by the use
of the layers of TaN and W, they are not especially limited, i.e.
both may be formed of an element selected from Ta, W, Ti, Mo, Al
and Cu or an alloy or compound material based on the element.
Otherwise, a semiconductor film may be used that is represented by
a polycrystal silicon film doped with an impurity element, such as
phosphorus.
[0097] Then, phosphorus is added at low concentration through the
gate electrode 807 and capacitance interconnection 808 as a mask in
a self-aligned fashion. In the region added at low concentration,
phosphorus concentration is controlled to
1.times.10.sup.16-5.times.10.sup.18/cm.sup.3, typically
3.times.10.sup.17-3.times.10.sup.18/cm.sup.3.
[0098] Next, a mask (not shown) is formed to add phosphorus at high
concentration to form a high-concentration impurity region to be
made into a source region 802 or drain region 803. In this
high-concentration impurity region, phosphorus concentration is
controlled to 1.times.10.sup.20-1.times.10.sup.21/cm.sup.3
(typically 2.times.10.sup.20-5.times.10.sup.20/cm.sup.3). The
semiconductor layer 805, in a region overlapped with the gate
electrode 807, is formed into a channel region 804. The region
covered by the mask is formed into a low-concentration impurity
region and into an LDD region 811. Furthermore, the region not
covered by any of the gate electrode 807, the capacitance line 808
and the mask is made as a high-concentration impurity region
including a source region 802 and a drain region 803.
[0099] Meanwhile, because this example forms p-channel TFTs to be
used for a drive circuit formed on the same substrate as the pixels
similarly to Example 1, the region to be formed into n-channel TFTs
is covered by a mask to add boron thereby forming a source or drain
region.
[0100] Then, after removing the mask, a first insulating film 810
is formed covering the gate electrode 807, the capacitance
interconnection 808 and interconnection (source line) 809. Herein,
a silicon oxide film is formed in a film thickness of 50 nm, and a
thermal process is carried out to activate the n-type or p-type
impurity element added at respective concentrations in the
semiconductor layer 805. Herein, thermal process is made at
850.degree. C. for 30 minutes (FIG. 8A). Incidentally, a pixel top
view herein is shown in FIG. 9. In FIG. 9, the sectional view taken
along the dotted line A-A' corresponds to FIG. 8A.
[0101] Then, after carrying out a hydrogenation process, a second
insulating film 811 is formed of an organic resin material. By
herein using an acryl film having a film thickness of 1 .mu.m, the
second insulating film 811 can be flattened in its surface. This
prevents the affection of a step caused by the pattern formed in
the layer beneath the second insulating film 811. Then, a mask is
formed on the second insulating film 811, to form by etching a
contact hole 812 reaching the semiconductor layer 805 (FIG. 8B).
After forming the contact hole 812, the mask is removed away.
[0102] Next, a 120-nm transparent conductive film (herein, indium
oxide-tin (ITO) film) is deposited by sputtering, and patterned
into a rectangular form by the use of a photolithography technique.
After carrying out a wet-etching treatment, heating treatment is
made in a clean oven at 250.degree. C. for 60 minutes thereby
forming a transparent electrode 813 (FIG. 8C). The pixel top view
herein is shown in FIG. 9. In FIG. 9, the sectional view taken
along the dotted line A-A' corresponds to FIG. 8C.
[0103] Next, a second conductive film is formed and patterned. Due
to this, formed are, besides a reflection electrode 814 formed on
the transparent electrode 813, an interconnection 815 electrically
connecting between the interconnection (source line) 809 and the
source region of TFT 820, an interconnection 816 forming a contact
with the drain region of TFT 820, and an interconnection 817
electrically connecting between the drain region of TFT 820 and the
transparent electrode 813. The second conductive film formed herein
is a reflective conductive film to form a reflection electrode of
the invention, which can use aluminum or silver, or otherwise an
alloy material based on these.
[0104] This example uses a layered film having a two-layer
structure continuously formed, by a sputter method, with a Ti film
having 50 nm as the second conductive film and a Si-contained
aluminum film having 500 nm.
[0105] The method of patterning uses a photolithography technique
to form a reflection electrode 814 comprising a plurality of
island-like patterns and interconnections 815, 816, 817. The method
for etching herein uses a dry etching scheme to carry out taper
etching and anisotropic etching.
[0106] At first, a resist mask is formed to carry out a first
etching process for taper etching. The first etching process is
under first and second etching conditions. For etching, an ICP
(Inductively Coupled Plasma) etching technique is suitably used.
Using the ICP etching technique, the film can be etched to a
desired taper form by properly controlling the etching condition
(amount of power applied to a coil-formed electrode, amount of
power applied to a substrate-sided electrode, electrode temperature
close to the substrate, etc.). The etching gas can suitably use a
chlorine-based gas represented by Cl.sub.2, BCl.sub.3, SiCl.sub.4,
CCl.sub.4 or the like, a fluorine-based gas represented by
CF.sub.4, SF.sub.6, NF.sub.3 or the like, or O.sub.2.
[0107] This example uses the ICP (Inductively Coupled Plasma)
etching technique, as a first etching condition, wherein BCl.sub.3,
Cl.sub.2 and O.sub.2 are used for an etching gas. Etching is
conducted with a plasma caused by feeding a 500 W RF (13.56 MHz)
power to a coil-formed electrode at a flow rate ratio of these
gasses of 65/10/5 (sccm) under a pressure of 1.2 Pa. A 300 W RF
(13.56 MHz) power is fed also to the substrate side (sample stage)
to apply substantially a negative self-bias voltage. Under the
first etching condition, the Si-contained aluminum film is etched
to make the first conductive layer at its end into a taper
form.
[0108] Thereafter, the mask is not removed for change to the second
etching condition. Using CF.sub.4, Cl.sub.2 and O.sub.2 for an
etching gas, etching is conducted for nearly 30 seconds with a
plasma caused by feeding a 500 W RF (13.56 MHz) power to the
coil-formed electrode at a flow rate ratio of these gasses of
25/25/10 (sccm) under a pressure of 1.2 Pa. A 20 W RF (13.56 MHz)
power is fed also to the substrate side (sample stage) to apply
substantially a negative self-bias voltage. Under the second
etching condition having CF.sub.4 and Cl.sub.2 mixed together, the
Si-contained aluminum film and the Ti film are both etched in the
same degree.
[0109] In this manner, by the first etching process, the second
conductive film comprising the first and second conductive layers
can be made into a taper form.
[0110] Then, the resist mask is not removed to carry out a second
etching process for anisotropic etching. Using herein BCl.sub.3 and
Cl.sub.2 for an etching gas, etching is conducted with a plasma
caused by feeding a 300 W RF (13.56 MHz) power to the coil-formed
electrode at a flow rate ratio of these gasses of 80/20 (sccm)
under a pressure of 1 Pa. A 50 W RF (13.56 MHz) power is fed also
to the substrate side (sample stage) to apply substantially a
negative self-bias voltage.
[0111] By the above, at a time that a reflection electrode 814 and
interconnections 815, 816 and 817 are formed, the resist is removed
to obtain a structure shown in FIG. 8D. Incidentally, a pixel top
view herein is shown in FIG. 10. In FIG. 10, the sectional view
taken along the dotted line A-A' corresponds to FIG. 8D.
[0112] In the above manner, this example also forms an active
matrix substrate having, on the same substrate, a pixel region
having double-gate-structured n-channel TFTs and holding
capacitances and a drive circuit having n-channel and p-channel
TFTs.
[0113] Meanwhile, according to the process shown in this example,
it is possible to simultaneously form a reflection electrode 814
and interconnections 815 816 and 817 by using a interconnection
pattern mask as shown in FIG. 8D. Consequently, the reflection
electrode can be formed separately in plurality in an island form
on a transparent electrode without increasing the number of
photo-masks required in fabricating an active matrix substrate. As
a result, in the manufacture of a transflective liquid crystal
display device, the process can be shortened thereby giving
contribution to manufacture cost reduction and yield
improvement.
Example 3
[0114] This example explains a method for manufacturing an active
matrix substrate different in structure from the one showing in
Examples 1 and 2.
[0115] In FIG. 12, over a substrate 1201 is formed a TFT 1215
having a gate electrode 1207, a source region 1202, a drain region
1203 and interconnections 1212 and 1213. The interconnections 1212
and 1213 are respectively, electrically connected to the source
region and the drain region.
[0116] Incidentally, the active matrix substrate of this example is
different from Examples 1 and 2 in that a transparent electrode
1211 is formed after forming the interconnections 1212 and
1213.
[0117] Similarly to the one showing in Example 1 or 2, a second
insulating film 1210 is formed and, after a contact hole is formed
therein, a second conductive film is formed. The material of the
second conductive film used herein can use the same material as
that of Example 1 or 2.
[0118] By patterning the second conductive film, it is possible to
form interconnections 1212 and 1213 and a reflection electrode
1214. Incidentally, a reflection electrode 1214 having a plurality
of island-like patterns can be formed by a method similar to the
method for forming the reflection film formed in Example 1 or 2.
However, because the reflection electrode 1214 of this example is
formed separately in an island form on the second insulating film
1210, during formation it is not electrically connected to the TFT
1215. Thereafter, an electrical connection can be formed by forming
the layer of a transparent conductive film 1211 on part of the
interconnection 1213 and on the reflection electrode 1214.
[0119] Incidentally, the active-matrix substrate fabricated in this
example, can be manufactured as a liquid crystal display device by
implementing the method shown in
Example 4
[0120] According to the example, steps of fabricating a
transflective type liquid crystal display device from the active
matrix substrate fabricated by Example 1 will be explained as
follows. A sectional view of FIG. 11 is used for explanation.
[0121] First, after obtaining the active matrix substrate of FIG.
3D in accordance with the example 1, as shown by FIG. 11, an
alignment film 1119 is formed on the active matrix substrate and
rubbing treatment is carried out. Further, according to the
example, after forming the alignment film 1119, spherical spacers
1121 for holding an interval between the substrates are scattered
over entire surfaces of the substrates. Further, in place of the
spherical spacers 1121, column-like spacers may be formed at
desired positions by patterning an organic resin film of an acrylic
resin film or the like.
[0122] Next, a substrate 1122 is prepared. A coloring layer 1123
(1123a, 1123b) and a flattening layer 1124 are formed on the
substrate 1122. Further, as the coloring layer 1123, a coloring
layer 1123a of red color, a coloring layer 1123b of blue color and
a coloring layer of green color (not illustrated) are formed.
Further, although not illustrated here, a light blocking portion
may be formed by partially overlapping the coloring layer 1123a of
the red color and the coloring layer 1123b of the blue color or
partially overlapping the coloring layer 1123a of the red color and
the coloring layer of the green color (not illustrated).
[0123] Further, an opposed electrode 1125 comprising a transparent
conductive film is formed on the flattening film 1124 at a position
for constituting a pixel portion, an alignment film 1126 is formed
over an entire face of the substrate 1122 and rubbing treatment is
carried out to thereby provide an opposed substrate 1128.
[0124] Further, the active matrix substrate formed with the
alignment film 1119 on the surface and the opposed substrate 1128
are pasted together by a seal agent (not illustrated). The seal
agent is mixed with a filler and two sheets of the substrates are
pasted together with a uniform interval (preferably, 2.0 through
3.0 .mu.m) therebetween by the filler and the spherical spacers.
Thereafter, a liquid crystal material 1127 is injected between the
two substrates and completely sealed by a seal agent (not
illustrated). A publicly known liquid crystal material may be used
for the liquid crystal material 1127. In this way, the
transflective type liquid crystal display device shown in FIG. 11
is finished. Further, as necessary, the active matrix substrate or
the opposed substrate 1128 is divided to cut in a desired shape.
Further, polarizers and the like are pertinently provided by using
a publicly known technology. Further, FPC is pasted thereto by
using the publicly known technology.
[0125] The constitution of the liquid crystal module provided in
this way will be explained in reference to a top view of FIG. 15. A
pixel portion 1504 is arranged at the center of an active matrix
substrate 1501. A source signal line drive circuit 1502 for driving
a source signal line is arranged on an upper side of the pixel
portions 1504. Gate signal line drive circuits 1503 for driving
gate signal lines are arranged on the left and on the right of the
pixel portion 1504. Although according to an example shown by the
example, the gate signal line drive circuits 1503 are symmetrically
arranged on the left and on the right of the pixel portion, the
gate signal line drive circuit 1503 may be arranged to only one
side thereof and a designer may pertinently select the side in
consideration of a substrate size of the liquid crystal module or
the like. However, the left and right symmetric arrangement shown
in FIG. 15 is preferable in consideration of operational
reliability and drive efficiency of circuit.
[0126] Signals are inputted to respective drive circuits from
flexible print circuits (FPC) 1505. According to FPC 1505, after
opening contact holes at an interlayer insulating film and a resin
film to reach a interconnection arranged at a predetermined
location of the substrate 1501 and forming a connection electrode
(not illustrated), FPC 1505 is pressed thereto via an anisotropic
conductive film or the like. According to the example, the
connection electrode is formed by using ITO.
[0127] At surroundings of the drive circuit and the pixel portion,
a seal agent 1507 is coated along the outer periphery of the
substrate and an opposed substrate 1506 is pasted in a state of
maintaining a constant gap (interval between the substrate 1501 and
the opposed substrate 1506) by spacers previously formed on the
active matrix substrate. Thereafter, liquid crystal elements are
injected from portions at which the seal agent 1507 is not coated
and the substrates are hermetically sealed by a seal agent 1508.
The liquid crystal module is finished by the above-described steps.
Further, although an example of forming all the drive circuits on
the substrates is shown here, several pieces of ICs may be used at
portions of the drive circuit. Thereby, the active matrix type
liquid crystal display device is finished.
Example 5
[0128] FIGS. 13 and 14 show block diagrams of an electro-optic
device manufactured in accordance with the present invention. Note
that FIG. 13 shows the structure of a circuit used for performing
analog driving. This example describes an electro-optic device
having a source side driver circuit 90, a pixel portion 91, and a
gate side driver circuit 92. The term driver circuit herein
collectively refers to a source side driver circuit and a gate side
driver circuit.
[0129] The source side driver circuit 90 is provided with a shift
register 90a, a buffer 90b, and a sampling circuit (transfer gate)
90c. The gate side driver circuit 92 is provided with a shift
register 92a, a level shifter 92b, and a buffer 92c. If necessary,
a level shifter circuit may be provided between the sampling
circuit and the shift register.
[0130] In this example, the pixel portion 91 is composed of a
plurality of pixels, and each of the plural pixels has TFT
elements.
[0131] Though not shown in the drawing, another gate side driver
circuit may be provided in across the pixel portion 91 from the
gate side driver circuit 92.
[0132] When the device is digitally driven, the sampling circuit is
replaced by a latch (A) 93b and a latch (B) 93c as shown in FIG.
14. A source side driver circuit 93 is provided with a shift
register 93a, the latch (A) 93b, the latch (B) 93c, a D/A converter
93d, and a buffer 93e. A gate side driver circuit 95 is provided
with a shift register 95a, a level shifter 95b, and a buffer 95c.
If necessary, a level shifter circuit may be provided between the
latch (B) 93c and the D/A converter 93d.
[0133] The above structure is obtained by employing the manufacture
process of either Example 1 or 2. Although this example describes
only the structure of the pixel portion and the driver circuit, a
memory circuit and a microprocessor circuit can also be formed when
following the manufacture process of the present invention.
Example 6
[0134] The transflective type liquid crystal display device
fabricated by carrying out the invention can be used in various
electro-optic devices. Further, the invention is applicable to all
electronic apparatus integrated with the electro-optic devices as
display media.
[0135] As electronic apparatus fabricated by using the liquid
crystal display device fabricated according to the invention, there
are pointed out a video camera, a digital camera, a navigation
system, a voice reproducing device (car audio, audio component), a
notebook type personal computer, a game machine, a portable
information terminal (mobile computer, cellular phone, portable
game machine or electronic book), device reproducing record media
of image reproducing device having record media (specifically,
digital video disk (DVD)) and having display devices capable of
displaying the image. FIGS. 16A to 16F show specific examples of
the electronic apparatus.
[0136] FIG. 16A is a digital still camera which includes a main
body 2101, a display portion 2102, an image receiving portion 2103,
an operation key 2104 and an outside connection port 2105 and a
shutter 2106. The digital still camera is fabricated by using the
liquid crystal display device fabricated by the invention at the
display portion 2102.
[0137] FIG. 16B is a notebook type personal computer which includes
a main body 2201, a cabinet 2202, a display portion 2203, a
keyboard 2204, an outside connection port 2205 and a pointing mouse
2206. The notebook type personal computer is fabricated by using
the liquid crystal display device fabricated by the invention at
the display portion 2203.
[0138] FIG. 16C shows a mobile computer which includes a main body
2301, a display portion 2302, a switch 2303, an operation key 2304
and an infrared ray port 2305. The mobile computer is fabricated by
using the liquid crystal display device fabricated by the invention
at the display portion 2302.
[0139] FIG. 16D shows a portable image reproducing device having a
record medium (specifically, DVD reproducing device) which includes
a main body 2401, a cabinet 2402, a display portion A 2403, a
display portion B 2404, a record medium (DVD etc) reading portion
2405, an operation key 2406, and a speaker portion 2407. The
display portion A 2403 mainly displays image information, the
display portion B 2404 mainly displays character information and
the portable image reproducing device is fabricated by using the
liquid crystal display device fabricated by the invention at the
display portions A, B 2403, 2404. Further, the image reproducing
device having the record media includes a game machine for
household use.
[0140] FIG. 16E shows a video camera which includes a main body
2601, a display portion 2602, a cabinet 2603, an outside connection
port 2604, a remote control receiving portion 2605, an image
receiving portion 2606, a battery 2607, a voice input portion 2608,
an operation key 2609 and an eye-piece portion 2610. The video
camera is fabricated by using the liquid crystal display device
fabricated by the invention at the display portion 2602.
[0141] Here, FIG. 16F shows a cellular phone which includes a main
body portion 2701, a cabinet 2702, a display portion 2703, a voice
input portion 2704, a voice output portion 2705, an operation key
2706, an outside connection port 2707 and an antenna 2708. The
cellular phone is fabricated by using the liquid display device
fabricated by the invention at the display portion 2703. Further,
the display portion 2703 can restrain power consumption of the
cellular phone by displaying a character of white color on the
background of black color.
[0142] As described above, the range of applying the liquid crystal
display device fabricated according to the invention is extremely
wide and electronic apparatus in all the fields can be fabricated.
Further, the electronic apparatus of the embodiment can be made by
using the liquid crystal display device fabricated by carrying out
Example 1 through Example 5.
[0143] By the above, by carrying out the present invention, because
the scatterbility of light can be enhanced by forming a
concavo-convex structure with using a transparent electrode and
reflection electrode in the manufacture of a transflective type
liquid crystal display device, display visibility can be improved.
Also, because a plurality of island-like patterns to be made into a
reflection electrode can be formed simultaneously with
interconnections by etching a conductive film, it is possible to
realize a great cost reduction and improvement in productivity.
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