U.S. patent application number 11/004085 was filed with the patent office on 2005-05-05 for liquid crystal display device and method for manufacturing the same.
Invention is credited to Kim, Cheol Se.
Application Number | 20050094047 11/004085 |
Document ID | / |
Family ID | 28450103 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050094047 |
Kind Code |
A1 |
Kim, Cheol Se |
May 5, 2005 |
Liquid crystal display device and method for manufacturing the
same
Abstract
A method for manufacturing the LCD device includes forming a
thin film transistor array having gate and data lines crossing to
each other, defining pixel regions on a substrate, and thin film
transistors arranged at crossings of the gate and data lines;
forming a passivation layer over the entire surface of the
substrate; forming a contact hole in the passivation layer exposing
drain electrodes of each thin film transistor; forming an amorphous
indium tin oxide film on the passivation layer; selectively
crystallizing portions of the amorphous indium tin oxide film
within the pixel regions by selectively irradiating light onto the
amorphous indium tin oxide thin film; and forming a pixel electrode
by selectively removing uncrystallized portions of the amorphous
indium tin oxide thin film.
Inventors: |
Kim, Cheol Se; (Boram Town,
KR) |
Correspondence
Address: |
MCKENNA LONG & ALDRIDGE LLP
1900 K STREET, NW
WASHINGTON
DC
20006
US
|
Family ID: |
28450103 |
Appl. No.: |
11/004085 |
Filed: |
December 6, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11004085 |
Dec 6, 2004 |
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10400508 |
Mar 28, 2003 |
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Current U.S.
Class: |
349/43 |
Current CPC
Class: |
G02F 1/13439 20130101;
G02F 1/136227 20130101 |
Class at
Publication: |
349/043 |
International
Class: |
G02F 001/136 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2002 |
KR |
2002-17361 |
Claims
1-19. (canceled)
20. A liquid crystal display (LCD) device, comprising: a substrate;
a plurality of gate lines; a plurality of data lines crossing the
plurality of gate lines, wherein the plurality of gate and data
lines defines a pixel region on the substrate; a thin film
transistor arranged at crossings of the plurality of gate and data
lines; and a pixel electrode formed of crystalline indium tin oxide
within the pixel region.
Description
[0001] This application claims the benefit of the Korean
Application No. P2002-17361 filed on Mar. 29, 2002, which is hereby
incorporated by reference for all purposes as if fully set forth
herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a liquid crystal display
(LCD) device and a method for manufacturing the same. More
particularly, the present invention relates to a method for
manufacturing a pixel electrode of a liquid crystal display (LCD)
device by irradiating portions of an amorphous indium tin oxide
(ITO) deposited on a passivation layer with light (e.g., an excimer
laser beam, UV light, etc.) to selectively form crystalline (or
polycrystalline) indium tin oxide and selectively etching the
uncrystallized portions of amorphous indium tin oxide.
[0004] 2. Discussion of the Related Art
[0005] Owing to their small size, reduced thickness and weight,
ability to display grayscales and moving pictures while consuming a
minimal amount of power, liquid crystal display (LCD) devices are
used as substitutes for cathode ray tubes (CRTs). LCD devices
generally comprise an LCD panel made up of a thin film transistor
(TFT) substrate and a color filter substrate separated from each
other by a layer of liquid crystal material.
[0006] The thin film transistor (TFT) substrate supports a
plurality of gate lines and data lines, crossing the gate lines.
Thin film transistors (TFTs) are formed at crossings of the gate
and data lines and pixel electrodes are formed in pixel regions
defined by the plurality of gate and data lines. The color filter
substrate supports a color filter layer and a common electrode. The
layer of liquid crystal material may be interposed between the two
substrates through an injection process. Electrodes are formed on
surfaces of the TFT and the color filter substrates such that the
surfaces of the two substrates supporting the electrodes face each
other and contact molecules of the layer of liquid crystal material
injected between the two substrates.
[0007] Images are displayed on the LCD panel by selectively
controlling the light transmittance characteristics of the layer of
liquid crystal material. Accordingly, electric fields, generated
upon the application of a voltage to the electrodes on the two
substrates, affect the orientation of molecules of the layer of
liquid crystal material to control the light transmittance
characteristics of the layer of liquid crystal material.
[0008] LCD devices known as active matrix LCD (AM-LCD) devices have
are capable of displaying images at high resolutions as well as
high quality moving images. AM-LCD devices include TFTs connected
to pixel electrodes arranged in a matrix pattern on a lower
substrate, a common electrode on an upper substrate, and a layer of
liquid crystal material interposed between the upper and lower
substrates. In AM-LCD devices, molecules of the layer of liquid
crystal material are driven by electric fields present between the
pixel and common electrodes and substantially perpendicular to the
lower and upper substrates.
[0009] A related art LCD device will now be explained in greater
detail.
[0010] FIG. 1A illustrates a schematic view of a related art LCD
device and FIG. 1B illustrates a cross-sectional view of the
related art LCD device of FIG. 1A taken along line I-I'.
[0011] Referring to FIG. 1A, the related art LCD device includes a
plurality of gate lines 1 and data lines 3 formed to cross each
other and to define a plurality of pixel regions, a plurality of
pixel electrodes 8 formed in respective ones of the pixel regions,
and a plurality of thin film transistors 7 formed at crossings of
the gate and data lines 1 and 3 capable of applying video signals
from the data lines 3 to corresponding pixel electrodes 8 in
response to signals from the gate lines 1. The gate and data lines
1 and 3 are made of a semitransparent material such as an aluminum
metal compound having a low resistance while the pixel electrodes 8
are made of a transparent material such as indium tin oxide
(ITO).
[0012] Referring to FIG. 1B, the gate line 1 is formed along a
first direction on a first substrate 9 and includes a gate
electrode 2 protruding from the gate line 1. Next, a gate
insulating layer 11 is formed over the entire surface of the first
substrate 1 and on the gate line 1. Next, an island-shaped
semiconductor layer 12 is formed on the gate insulating layer 11 in
a region above the gate electrode 2. The data line 3 is formed on
the gate insulating layer 11 along a second direction,
substantially perpendicular to the first direction. A source
electrode 5a is formed to protrude from the data line 3 and extend
over a first side of the semiconductor layer 12 while a drain
electrode 5b is formed to extend over a second side of the
semiconductor layer 12, opposite the first side, and spaced apart
from the source electrode 5a by a predetermined distance.
Accordingly, a thin film transistor (TFF) 7 is formed where each of
the gate and data lines 1 and 3 cross each other.
[0013] Subsequently, a passivation layer 13 is formed over the
entire surface of the first substrate 9 and on the thin film
transistor 7. Further, a contact hole is formed in a portion of the
passivation layer over the drain electrode 5b. The pixel electrode
8 is then formed on the passivation layer 13 in the pixel region
and is electrically connected to the drain electrode 5b through the
contact hole. Next, a first alignment layer 17a, capable of
regularly orienting liquid crystal molecules, is formed over the
entire surface of the first substrate 9 and on the pixel electrode
8 and passivation layer 13.
[0014] Still referring to FIG. 1B, a second substrate 10 supports a
black matrix layer 14 for preventing light leakage in regions
outside the pixel region of the first substrate 9 (i.e., regions
corresponding to the gate line 1, the data line 3, and the thin
film transistor 7), Red/Green/Blue (R/G/B) color filter layers 15
for selectively transmitting light having predetermined wavelengths
formed within each pixel region, a common electrode 16 having a
potential different from that of the pixel electrode 8, and a
second alignment layer 17b, capable of regularly orienting liquid
crystal molecules, formed over the common electrode 16.
[0015] Subsequently, spacers (not shown) and sealant material (not
shown) are formed between the first and second substrates 9 and 10,
to bond the first and second substrates 9 and 10 together and to
uniformly separate the bonded substrates by predetermined distance.
Finally, liquid crystal material is injected between the bonded
substrates 9 and 10 to form a layer of liquid crystal material
23.
[0016] Techniques used in manufacturing the aforementioned LCD
device are similar to those used in manufacturing silicon
semiconductors. For example both techniques involve thin film
deposition process steps and process steps involving the
photolithographic patterning of the thin film (e.g., photoresist
(PR) deposition, ultraviolet (UV) exposure and developing, etching,
and PR strip and cleaning process steps). Accordingly, the
aforementioned method of manufacturing LCD devices requires
repetitive process steps to form thin films.
[0017] FIGS. 2A to 2F illustrate cross-sectional views of process
steps required to manufacture the related art LCD device.
[0018] Referring first to FIG. 2A, to manufacture the related art
LCD devices, a metal layer is deposited on a first substrate 9 and
patterned so as to form a gate line 1 and gate electrode 2. Next, a
gate insulating layer 11 is deposited over the entire surface of
the first substrate 9. Next, the semiconductor layer 12 is
deposited over the entire surface of the first substrate 9 and is
selectively removed, leaving an island-shaped semiconductor layer
12 above the gate electrode 2, wherein the island-shaped
semiconductor layer 12 constitutes the active layer of the thin
film transistor (TFT).
[0019] Subsequently, a metal layer is deposited over the entire
surface of the first substrate 9 and patterned so as to form a data
line 3 and source/drain electrodes 5a and 5b, respectively. A
passivation layer 13 is formed over the entire surface of the first
substrate 9 and on the data line 3. Next, a portion of the
passivation layer 13 is selectively removed to form a contact hole
exposing the drain electrode 5b. An amorphous indium tin oxide film
(a-ITO) is then deposited on the passivation layer 13 in a low
temperature sputtering process such that the a-ITO film
electrically contacts the drain electrode 5b through the contact
hole.
[0020] Referring to FIG. 2B, a photoresist layer 20 is deposited on
the a-ITO film 8a and is subsequently hardened in a baking
process.
[0021] Referring to FIG. 2C, a mask 21 is positioned above the
photoresist layer 20. Regions of the photoresist layer 20 not
directly underlying the mask 21 are then exposed to ultraviolet
rays 22.
[0022] Referring to FIG. 2D, portions of the photoresist layer 20
that were exposed to the UV light are removed in a developing
process.
[0023] Referring to FIG. 2E, portions of the a-ITO film 8a, exposed
upon the removal of portions of the photoresist layer 20, are
etched using an etchant wherein the remaining portions of the
photoresist layer 20 act as an etch mask. Generally, etchants such
as diluted oxalic acid or diluted hydrochloric acid are used to
etch a-ITO films.
[0024] Referring to FIG. 2F, the remaining photoresist layer 20 is
stripped, the substrate is cleaned, and a pixel electrode 8 is thus
formed.
[0025] The related art method described above forms the pixel
electrode 8 by patterning an amorphous indium tin oxide film
deposited on a passivation layer via conventional photolithography
and etching processes. Accordingly, the related art method
described above is disadvantageous because forming pixel electrodes
via conventional photolithography processes (e.g., depositing
photoresist layer on the amorphous indium tin oxide thin film,
exposing the photoresist layer, developing the photoresist layer,
etching the amorphous indium tin oxide thin film using the
photoresist layer as an etch mask, stripping the photoresist layer,
and cleaning the substrate) increases the risk of generating
defects and decreases the yield due to the application of
complicated and time consuming photolithographic steps. Further,
the monetary expense and time required to install and maintain
photolithographic equipment and consistent patterning procedures
can be prohibitively excessive.
SUMMARY OF THE INVENTION
[0026] Accordingly, the present invention is directed to a liquid
crystal display (LCD) device and a method for manufacturing the
same that substantially obviates one or more problems due to
limitations and disadvantages of the related art.
[0027] An advantage of the present invention provides an LCD device
and a method for manufacturing the same that is capable of
simplifying manufacturing process steps and improving LCD device
yield wherein a pixel electrode is formed by selectively
irradiating portions of an amorphous indium tin oxide (ITO)
deposited on a passivation layer with light (e.g., an excimer laser
beam, UV light, etc.) to selectively form crystalline (or
polycrystalline) indium tin oxide. Uncrystallized amorphous indium
tin oxide may then be selectively etched with respect to
crystalline (or polycrystalline) indium tin oxide.
[0028] Additional advantages and features of the invention will be
set forth in the description which follows and in part will become
apparent from the description, or may be learned by practice of the
invention. These and other advantages of the invention will be
realized and attained by the structure particularly pointed out in
the written description and claims hereof as well as the appended
drawings.
[0029] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described herein, a method for manufacturing a liquid crystal
display (LCD) device may, for example, include forming a thin film
transistor array having gate and data lines crossing each other on
a substrate and defining pixel regions; forming thin film
transistors at crossings of the gate and data lines; forming a
passivation layer over the entire surface of the substrate; forming
a contact hole in a portion of the passivation layer in a region
over a drain electrode of each thin film transistor; forming an
amorphous indium tin oxide film on the passivation layer;
selectively crystallizing the amorphous indium tin oxide by
selectively irradiating light to portions of the amorphous indium
tin oxide film within the pixel region; and forming a pixel
electrode by selectively removing uncrystallized portions of the
amorphous indium tin oxide film.
[0030] In one aspect of the present invention, the amorphous indium
tin oxide film may be selectively crystallized by, for example,
positioning a mask shielding regions outside the pixel regions and
exposing regions within the pixel regions and irradiating light
onto the exposed portions of the amorphous indium tin oxide film
but not onto the shielded portions of the amorphous indium tin
oxide film.
[0031] In another aspect of the present invention, the light may
comprise an excimer laser beam or UW light.
[0032] In yet another aspect of the present invention, portions of
the amorphous indium tin oxide film that are not crystallized may
be selectively removed by an etchant such as diluted oxalic acid,
diluted hydrochloric acid, or a weak acid comprising diluted oxalic
acid and diluted hydrochloric acid.
[0033] In still another aspect of the present invention, the
concentration of diluted oxalic acid may be about 10% or less.
[0034] In yet another aspect of the present invention, the
amorphous indium tin oxide film may be etched by the etchant at a
temperature of about 60.degree. C. or less.
[0035] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiment(s) of
the invention and together with the description serve to explain
the principle of the invention.
[0037] In the drawings:
[0038] FIG. 1A illustrates a schematic view of a related art LCD
device;
[0039] FIG. 1B illustrates a cross-sectional view of the related
art LCD device of FIG. 1A taken along line I-I';
[0040] FIGS. 2A to 2F illustrate cross-sectional views of process
steps required to manufacture the related art LCD device;
[0041] FIGS. 3A to 3C illustrate cross-sectional views of process
steps required to manufacture an LCD device according to the
principles of the present invention; and
[0042] FIG. 4 is a graph illustrating the dependence of the etching
rates of amorphous and crystalline indium tin oxide films on
etching temperature.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0043] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings.
[0044] A method for manufacturing an LCD device according to the
principles of the present invention will now be explained.
[0045] FIGS. 3A to 3C illustrate cross-sectional views of process
steps required to manufacture an LCD device according to the
principles of the present invention.
[0046] Referring to FIG. 3A, a metal layer may be deposited onto a
glass or quartz substrate 109 and patterned into a gate line (not
shown), similar to gate line 1 shown in FIG. 1A, and a gate
electrode 102. Next, a gate insulating layer 111 and a
semiconductor layer may be sequentially deposited over the entire
surface of the substrate 109 and on the gate electrode 102.
Portions of the semiconductor layer may then be selectively removed
to form an island-shaped semiconductor layer 112 above the gate
electrode 102, wherein the island-shaped semiconductor layer 112
constitutes the active layer of a thin film transistor (TFT).
[0047] Subsequently, a metal layer may be deposited over the entire
surface of the substrate 109 and patterned so as to form a data
line 103 and source/drain electrodes 105a and 105b, respectively. A
passivation layer 113 may be formed over the entire surface of the
substrate 109 on the drain electrode 105b. Next, a portion of the
passivation layer 113 may be selectively to form a contact hole
exposing the drain electrode 105b.
[0048] Still referring to FIG. 3A, after the contact hole is formed
in the passivation layer 113, an amorphous indium tin oxide (a-ITO)
film 108a may be formed on the passivation layer 113. In one aspect
of the present invention, the amorphous indium tin oxide film 108a
may be formed by a sputtering deposition process. In another aspect
of the present invention, the amorphous indium tin oxide film 108a
may be formed to electrically contact the drain electrode 105b
through the contact hole in the passivation layer 113. In one
aspect of the present invention, the amorphous indium tin oxide
film 108a may, for example, be formed using a target comprising
indium tin oxide. In another aspect of the present invention, a
predetermined amount of H.sub.2O or zinc (Zn) may be added to the
target. In yet another aspect of the present invention the
sputtering process may be performed at a low temperature.
[0049] Referring to FIG. 3B, a mask 121 may be positioned above a
portion of the substrate 109 where a pixel electrode is not to be
formed, exposing portions of the amorphous indium tin oxide 108a in
regions where a pixel electrode is to be formed. Subsequently,
light (e.g., an excimer laser beam, UV light, etc.) 122 may be
selectively irradiated onto portions of the amorphous indium tin
oxide film 108a exposed by the mask 121. According to the
principles of the present invention, the irradiating light 122 may
be characterized as having a predetermined energy and wavelength
capable of crystallizing the amorphous indium tin oxide film 108a.
Upon being irradiated with the light 122, only the exposed portions
of the amorphous indium tin oxide film 108a are crystallized and a
crystalline (or polycrystalline) indium tin oxide film 108b may be
selectively formed in regions where a pixel electrode is to be
formed.
[0050] Referring to FIG. 3C, portions of the amorphous indium tin
oxide film 108a, masked from the irradiating light 122 by the mask
121, may be etched using an etchant. In one aspect of the present
invention, an etchant such as a diluted oxalic acid having a
concentration of about 10% or less or a diluted hydrochloric acid
may be used to selectively etch the amorphous indium tin oxide film
108a with respect to the crystallized (or polycrystalline) indium
tin oxide film 108b. In one aspect of the present invention, the
diluted oxalic acid may have a concentration of between about 2%
and about 5%. In another aspect of the present invention, the
diluted oxalic acid may have a concentration of about 3%.
[0051] Referring to Table 1, the etching rates of the amorphous
indium tin oxide film 108a and the crystalline (or polycrystalline)
indium tin oxide film 108b in diluted oxalic acid having a
concentration of about 10% vary according to the etching
temperature.
1 TABLE 1 Etching rate (.ANG./sec) Tempera- Flux Amorphous indium
Crystalline/polycrystalline ture (.degree. C.) (l/m) tin oxide
indium tin oxide 25 30 7.9 0.0 30 30 11.1 0.0 35 30 14.3 0.0 65 30
-- 1.2
[0052] As shown in Table 1, etching rates of various forms of
indium tin oxide generally increase as the temperature of the
etchant increases. In present invention, a significant amount of
amorphous indium tin oxide is etched in diluted oxalic acid across
low to high etching temperatures. However, the amount of
crystalline (or polycrystalline) indium tin oxide material etched
by diluted oxalic acid across the same temperature range is
negligible compared to the amount by which amorphous indium tin
oxide is similarly etched. Table 1 can be equivalently represented
by the graph illustrated in FIG. 4. In view of Table 1 and FIG. 4,
an amorphous indium tin oxide film 108a having a thickness of
hundreds of angstroms can be completely etched by diluted oxalic
acid in hundred seconds at room temperature while a negligible
amount of crystalline (or polycrystalline) indium tin oxide is
etched by the diluted oxalic acid across the same range of etching
temperatures.
[0053] According to the principles of the present invention, the
irradiating light (e.g., excimer laser beam, UV light, etc.) 122
may be selectively irradiated onto the amorphous indium-tin oxide
film 108a so as to selectively form a pixel electrode made out of
crystalline (or polycrystalline) indium tin oxide film 108b.
Further, portions of the amorphous indium tin oxide 108a outside
the pixel region and not irradiated by the light 122 may be
selectively etched with respect to the portions of the amorphous
indium tin oxide 108a within the pixel region and irradiated by the
light 122.
[0054] According to the principles of the present invention,
etching the amorphous indium tin oxide film 108a selectively with
respect crystalline (or polycrystalline) indium tin oxide film 108b
with an etchant such as diluted oxalic acid, diluted hydrochloric
acid, etc., results in reduced manufacturing cost and time compared
to related art fabricating techniques such as those illustrated in
FIGS. 2A-2F, thereby improving yield.
[0055] According to the principles of the present invention, the
amorphous indium tin oxide thin film 108a may be deposited on the
passivation layer 113. Subsequently, the amorphous indium tin oxide
thin film 108a may be selectively irradiated with light 122 (e.g.,
excimer laser beam, UV light, etc.) to selectively crystallize
portions of the amorphous indium tin oxide 108a into a crystalline
(or polycrystalline) indium tin oxide film 108b. Portions of the
amorphous indium tin oxide film 108a not irradiated with the light
122 may be selectively etched with respect to the portions of the
amorphous indium tin oxide film 108b irradiated with the light 122
using an etchant such as diluted oxalic acid, diluted hydrochloric
acid, and the like. Accordingly, it is possible to form a pixel
electrode made out of crystalline (or polycrystalline) indium tin
oxide.
[0056] As mentioned above, the method for manufacturing the LCD
device according to the principles of the present invention is
advantageous because amorphous indium tin oxide material not
selectively irradiated by light having a predetermined energy and
wavelength may be selectively etched with respect to amorphous
indium tin oxide material that has been selectively irradiated by
light having a predetermined energy and wavelength using an
etchant. Accordingly, a pixel electrode may be formed out of the
amorphous indium tin oxide material that has been selectively
irradiated by light having a predetermined energy and wavelength.
Thus, the method for manufacturing the LCD device according to the
principles of the present invention results in reduced
manufacturing cost and time compared to related art fabricating
techniques such as those illustrated in FIGS. 2A-2F, thereby
improving yield.
[0057] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *