U.S. patent application number 10/310590 was filed with the patent office on 2003-06-26 for method of manufacturing full-color organic electro-luminescent device.
Invention is credited to Chang, En-Chung, Chao, Ching-Ian, Hsieh, Chia-Fen, Tsai, Rung-Ywan.
Application Number | 20030118950 10/310590 |
Document ID | / |
Family ID | 21660677 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030118950 |
Kind Code |
A1 |
Chao, Ching-Ian ; et
al. |
June 26, 2003 |
Method of manufacturing full-color organic electro-luminescent
device
Abstract
A method of manufacturing a full-color organic
electro-luminescent device on an indium-tin-oxide glass substrate.
A pattern is formed on the indium-tin-oxide glass substrate by the
photolithography and the etching process. The indium-tin-oxide
glass substrate is cleaned. An insulation pad is formed over the
indium-tin-oxide glass substrate. A low shadow mask and a high
shadow mask are sequentially formed over the insulation pad by
conducting dry film photo-resist processes. A hole-transport layer
is formed over the indium-tin-oxide glass substrate by conducting a
vapor-depositing process. Three vapor-depositing processes are
simultaneously conducted to form red, green and blue light-emitting
layers on the hole-transport layer using the low shadow mask and
the high shadow mask as a barrier. An electron-transport layer and
a metal layer are serially formed over the light-emitting layers by
conducting vapor-depositing processes.
Inventors: |
Chao, Ching-Ian; (Hsinchu
Hsien, TW) ; Chang, En-Chung; (Yunlin Hsien, TW)
; Hsieh, Chia-Fen; (Tainan, TW) ; Tsai,
Rung-Ywan; (Taoyuan Hsien, TW) |
Correspondence
Address: |
J.C. Patents
Suite 250
4 Venture
Irvine
CA
92618
US
|
Family ID: |
21660677 |
Appl. No.: |
10/310590 |
Filed: |
December 4, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10310590 |
Dec 4, 2002 |
|
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09715527 |
Nov 17, 2000 |
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6517996 |
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Current U.S.
Class: |
430/321 ;
430/315; 430/319 |
Current CPC
Class: |
H01L 27/3283 20130101;
H01L 27/3211 20130101; H01L 2251/558 20130101; C23C 14/0015
20130101; H01L 27/3246 20130101; H01L 51/56 20130101; C23C 14/225
20130101; H01L 51/0011 20130101; H01L 51/001 20130101 |
Class at
Publication: |
430/321 ;
430/319; 430/315 |
International
Class: |
H01J 009/227 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2000 |
TW |
89115831 |
Claims
What is claimed is:
1. A method of manufacturing a full-color organic
electro-luminescent device, comprising the steps of: patterning an
indium-tin-oxide glass substrate; cleaning the indium-tin-oxide
glass substrate; forming an insulation pad over the
indium-tin-oxide glass substrate; forming a low shadow mask over
the insulation pad by the first dry film photo-resist process;
forming a high shadow mask over the insulation pad by conducting
the second dry film photo-resist process; forming a hole-transport
layer over the indium-tin-oxide glass substrate by conducting a
vapor-depositing process; conducting three vapor-depositing
processes simultaneously to form the red, the green and the blue
light-emitting materials on the hole-transport layer in the same
step using the low shadow mask and the high shadow mask as a
barrier; forming an electron-transport layer over the red, the
green and the blue light-emitting materials by conducting a
vapor-depositing process; and forming a metal layer over the
electron-transport material by conducting a vapor-depositing
process.
2. The method of claim 1, wherein material forming the insulation
pad is selected from the group consisting of silicon nitride and
silicon oxide.
3. The method of claim 1, wherein the low shadow mask has a
thickness between 1 .mu.m to 10 .mu.m.
4. The method of claim 1, wherein the high shadow mask has a
thickness between 5 .mu.m to 100 .mu.m.
5. The method of claim 1, wherein material forming the
hole-transport layer includes N,N'-diphenyl-N,N'-(m-tolyl)
benzidine.
6. The method of claim 1, wherein the hole-transport layer has a
thickness between 40 nm to 80 nm.
7. The method of claim 1, wherein the blue vapor-depositing
material used in the simultaneous vapor-depositing process includes
perylene.
8. The method of claim 1, wherein the thickness of the red, the
green and the blue light-emitting materials is between 15 nm to 30
nm.
9. The method of claim 1, wherein the step of performing a
simultaneous vapor-depositing process includes providing a
blue-light-emitting-materia- l evaporation source, a
red-light-emitting-material evaporation source and a
green-light-emitting-material evaporation source.
10. The method of claim 1, wherein material forming the red
sub-pixels includes nile red and material forming the green
sub-pixels includes quinacridone.
11. The method of claim 9, wherein the evaporation sources for the
red and the green sub-pixels are positioned on each side of the
blue material evaporation source.
12. The method of claim 9, wherein the step of forming the blue
sub-pixels includes aiming a beam of blue material from the blue
evaporation source front at the surface of the indium-tin-oxide
glass substrate in a vapor-depositing process.
13. The method of claim 9, wherein the step of forming the red
sub-pixels and the green sub-pixels includes aiming a beam of red
material from the red evaporation source and a beam of green
material from the green evaporation source simultaneously at the
indium-tin-oxide glass substrate surface both tilted at an
identical angle from the vertical but on opposite side.
14. The method of claim 11, wherein the angle of tilt from the
vertical is between 45.degree. to 80.degree..
15. The method of claim 11, wherein the red and the green
light-emitting materials in the blue light-emitting material are
controlled at a percentage between 0.5% to 5% by volume ratio.
16. The method of claim 1, wherein material forming the
electron-transport layer includes tris-(8-hydroxyquinoline)
aluminum.
17. The method of claim 1, wherein the electron-transport layer has
a thickness between 40 nm to 80 nm.
18. The method of claim 1, wherein the evaporation source for
depositing metal layer is set at an angle of tilt from a vertical
to the indium-tin-oxide glass substrate surface.
19. The method of claim 18, wherein the angle of tilt is between
5.degree. to 60.degree..
20. The method of claim 1, wherein material forming the metal layer
is selected from the group consisting of calcium, magnesium,
lithium, aluminum and silver.
21. The method of claim 1, wherein the metal layers include a layer
of magnesium and a layer of silver.
22. The method of claim 21, wherein the magnesium layer has a
thickness between 30 nm to 70 nm.
23. The method of claim 21, wherein the silver layer has a
thickness between 200 nm to 350 nm.
24. The method of claim 1, wherein the metal layer is a negative
electrode.
25. The method of claim 1, wherein the indium-tin-oxide glass
substrate is a positive electrode.
26. The method of claim 1, wherein the insulation pad has a
thickness between 5 .mu.m to 200 .mu.m.
27. A processing station for manufacturing a full-color organic
electro-luminescent device, comprising: a plurality of evaporation
source packs with each evaporation source pack having at least one
evaporation source, wherein each evaporation source pack can be
used for vapor-depositing various types of materials; a plurality
of cassettes with each cassette capable of holding one
indium-tin-oxide glass substrate; and a conveyer belt for moving
the cassettes that hold indium-tin-oxide glass substrate
continuously in such a way that each cassette passes in front of
each evaporation source pack sequentially to carry out the required
vapor-depositing processes.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Taiwan
application serial no. 89115831, filed Aug. 7, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to a method of manufacturing a
full-color organic electro-luminescent (OEL) device. More
particularly, the present invention relates to a method of
manufacturing a full-color organic electro-luminescent (OEL) device
using a special designed process and equipment, in which the
dry-film photo-resist as the shadow mask is made on the insulated
pad and the deposition of RGB sub-pixels is carried out in the same
time.
[0004] 2. Description of Related Art
[0005] Investigation of on organic electro-luminescent material
began in the 1960s and more than 30 years of research data has been
accumulated right now. When the investigation of single crystal
organic compound was first reported in 1963, a high voltage of
around 400 volts had to be applied before luminescent occurs. Yet,
the brightness level produced by the luminescent material is too
weak to have any real-life application.
[0006] In 1987, Kodak in America reported some success in producing
organic low-molecular-weight electro-luminescent device in Appl.
Phys. Lett., Vol.51, p914(1987). In 1990, Cambridge University in
England was similarly successful in utilizing the polymer material
to produce electro-luminescent devices in Nature, Vol.347, p539
(1990). From these earlier researches, foundation for investigating
actual application of electro-luminescent devices by governments,
institutes and academies is laid.
[0007] Highly desirable properties of electro-luminescent material
include self-illumination, wide viewing angle (up to 160.degree.),
rapid response, low driving voltage and full-color spectrum. Hence,
electro-luminescent been highly regarded as the planar display
techniques of the future. At present, the development of
electro-luminescent devices has reached such a high degree of
sophistication that electro-luminescent display can be out in the
next generation of planar color displays. These planar luminescent
devices can be used in high-quality, full-color planar displays
such as miniature display panel, outdoor display panel, computer
and television screens.
[0008] At present, research in electro-luminescent products is
directed towards the investigation of device and material
structure. Rapid development in low-molecular-weight
electro-luminescent material has produced the first prototype
full-color organic electro-luminescent display. However, some
technical problems still prevent the use polymer material in
full-color organic electro-luminescent devices. One major
difficulty lies in the alignment of red-green-blue (R-G-B)
sub-pixels in the spin-coating process.
[0009] Color display techniques using organic electro-luminescent
material can be roughly divided into two sub-categories, namely,
direct full-color display techniques and indirect full-color
display techniques.
[0010] Literature of direct full-color display techniques
includes:
[0011] 1. A full-color electro-luminescent device structure having
micro-cavities of various depths is developed in Cambridge (Adv.
Mater., Vol.7, p541 (1996); Synth. Met., Vol. 76, p137(1996)), by
Cimrova et. el (Appl. Phys. Lett., Vol. 69, p608 (1996)); in Bell
Lab and Motorola (R.O.C patent no. 301,802, 318,284, 318,966).
However, the method of production is rather complicated.
Furthermore, producing micro-cavities at different depth levels is
a high-cost process.
[0012] 2. A method of stacking organic electro-luminescent element
capable of emitting blue light and organic electro-luminescent
element capable of emitting red light on top of a substrate is
developed jointly by Princeton and Southern California University
(Appl. Phys. Lett., Vol.69, p2959 (1996)); R.O.C. patent no.
294,842). However, the method uses difficult fabrication
techniques. Moreover, the metal electrodes between the
light-emitting element blocks off a portion of the red and green
light, thereby lowering the brightness level.
[0013] 3. A method that uses X-Y addressing pattern for fabricating
a full-color organic electro-luminescent device capable of
different color pixels is developed by Kodak Co. of America (U.S.
Pat. Nos. 5,294,869 and 5,294,870). It utilizes the shift of metal
mask to form R-G-B individual sub-pixels in the deposition process
so that it is not good for the applications of higher resolution
and larger substrate.
[0014] 4. A method of fabricating full-color organic
electro-luminescent device by photo bleaching is developed by
professor Kido of Japan. The method uses light to damage the
resonance structure of red-energy-gap material of the
light-emitting layer so that energy gap of the material is
increased, green-blue-red pixels are formed and pixels of different
colors are fixed for full-color display.
[0015] Besides the aforementioned production methods, a method that
utilizes an ink-jet printing technique instead of spin-coating to
fabricate a polymer electro-luminescent device is developed by Yang
Yang (Science, Vol.279, p1135(1990)). The method can reduce the
consumption of polymer material and can produce whatever display
pattern and words. Size of ink drop can be as small as 30 .mu.m.
The method can be applied to produce a full-color display device.
However, this method is new and many technical problems still
exists. Problems such as the transportation of indium-tin oxide
glass, the type of solvents to be used and the blocking of inkjet
nozzle need to be addressed.
[0016] Literature of indirect full-color display techniques
includes:
[0017] 1. TDK Co. has developed a full-color organic
electro-luminescent device that uses a color filter. First, a
conventional method is used to fabricate a white light
electro-luminescent component. Red, green and blue color filters
are added to the white-light-emitting pixels so that the white
light is converted into red, green and blue light respectively.
Although this method is capable of producing a full-color display
device from a white-light-emitting component, the filters greatly
reduce light intensity of the device.
[0018] 2. A full-color organic electro-luminescent device having a
color conversion layer has been developed by Idemitsu Kosan. The
device has a structure similar to a light-emitting device with
filters. Although light conversion of the blue light can be used to
produce a full-color display device, the process of forming
separating column is complicated. Moreover, using a conversion
layer for red, green and blue will lower light intensity of the
device.
[0019] Apart from the previous methods, another direct full-color
display technique similar to this invention is presented and
compared as below.
[0020] Kodak of America has introduced an X-Y address-patterning
method for producing a full-color organic electro-luminescent
device in U.S. Pat. No. 5,294,869. FIGS. 1A through 1E are
schematic cross-sectional views showing the steps for producing a
full-color organic electro-luminescent device according to a
conventional X-Y addressing pattern. First, as shown in FIG. 1A, a
vertical shadow mask is formed over an indium-tin-oxide glass
substrate 100 by a wet photo-resist production or a dielectric film
deposition method. As shown in FIG. 1B to FIG. 1D, three vapor
deposition operations are carried out to deposit red, green and
blue color materials. In the first vapor deposition operation 104
shown in FIG. 1B, a first type of material is deposited on the
substrate 100 at an angle .theta..sub.1 to form a sub-pixel 106. In
the second vapor deposition operation 108 as shown in FIG. 1C, a
second type of material is deposited on the substrate 100 at a
negative angle .theta..sub.1 to form a sub-pixel 110. In the third
vapor deposition operation 112 shown in FIG. 1D, a third type of
material is deposited on the substrate 100 vertically to form a
sub-pixel 114. As shown in FIG. 1E, a metal layer 116 is formed by
the fourth vapor deposition operation 118 at an angle
.theta..sub.2. Utilizing the vertical shadow mask 102, the
interconnection between sub-pixels is prevented. Although this
method is able to produce a full-color display device, in fact, a
few problems remain. The problems include:
[0021] (I) The process of forming a vertical shadow mask: Since a
wet photo-resist production or a dielectric film deposition method
is used to form the shadow mask, thickness of the mask 102 can
hardly rise above 20 .mu.m. In addition, forming a mask having
uniform thickness on a large-area substrate is difficult. If
thickness of the mask layer is non-uniform, subsequent positioning
and size of red, green and blue sub-pixels are all affected.
[0022] (II) Shadow effect: The design of most conventional
evaporator for deposition organic electro-luminescent material
requires the substrate to be fastened onto a rotary holder. When
the deposition starts, the substrate rotates so that a uniform
layer is formed. However, the substrate must be fixed in position
in the shadow-mask process, so that a material beam can shine on
the substrate at a fixed angle. Consequently, rotary deposition is
not suitable for the shadow-mask process. Although any
non-uniformity of the vapor-deposited layer on a substrate when the
substrate doesn't rotate can be reduced by calibration, a
non-rotating substrate renders every point on the substrate having
a slightly different angle relative to a vaporizing source. This
can lead to variations in position and size of red, green, blue
sub-pixels on the substrate. This phenomenon is all the more
serious when the substrate has a large surface area.
[0023] (III) Leakage current in the device: As shown in FIG. 1E,
only a layer of organic film is deposited over the substrate at
position 120 on the right side of some shadow mask layer. This
thinner portion can result in considerable leakage current when a
metal layer is subsequently deposited to serve as an electrode.
This is also an area where short-circuiting is more likely to occur
leading to device failure.
[0024] A conventional evaporator for vapor deposition has
independent evaporation chambers. Indium-tin-oxide glass substrates
are moved into different evaporation chamber by robotic hands to
perform different vapor deposition processes. During the vapor
deposition process, the indium-tin-oxide glass substrate must
rotate continuously to form a uniformly coated film. Hence, a
conventional evaporator is unsuitable for the shadow mask process.
In addition, a convention evaporator operates on a unit-by-unit
basis rather than a continuous production flow. Therefore, spatial
utilization of the evaporation chamber is low. Furthermore, size of
the evaporation chamber limits the ultimate size of the
indium-tin-oxide glass substrate. To achieve higher stability in
the production process, sophisticated robotic control system has to
be deployed. This also adds to the production cost of an
evaporator.
SUMMARY OF THE INVENTION
[0025] Accordingly, one object of the present invention is to
provide a method of manufacturing a high-efficiency full-color
organic electro-luminescent device with the direct full-color
display technique.
[0026] A second object of this invention is to provide a method of
manufacturing a full-color organic electro-luminescent device
capable of self-positioning red, blue and green sub-pixels on a
substrate concurrently so that the alignment steps in the
traditional metal mask process are saved.
[0027] A third object of this invention is to provide a method of
manufacturing a full-color organic electro-luminescent device that
employs a unique insulation pad capable of preventing shadow effect
that may lead to a leakage current in the device. Hence, production
yield of the device is increased.
[0028] A fourth object of this invention is to provide a processing
station design that facilitates the manufacturing of the full-color
organic electro-luminescent device of this invention.
[0029] To achieve these and other advantages and in accordance with
the purpose of the invention, as embodied and broadly described
herein, the invention provides a method of manufacturing a
full-color organic electro-luminescent device. An indium-tin-oxide
glass substrate is provided. The indium-tin-oxide glass substrate
is etched to form a desired pattern. The glass substrate is
cleaned. An insulation pad is formed over the glass substrate by
carrying out a photo-resist processing and a film-deposited
operation. A patterned shadow mask is formed on the glass substrate
by performing a dry film photo-resist processing. The shadow mask
pattern can be subdivided into two types. One type of shadow mask
has a thickness of about 1 .mu.m to 10 .mu.m, commonly referred to
as a low shadow mask (LSM). Another type of shadow mask has a
thickness of about 5 .mu.m to 100 .mu.m, commonly referred to as a
high shadow mask (HSM). The indium-tin-oxide glass substrate is
cleaned again. Hole-transport material such as
N,N'-diphenyl-N,N'-(m-tolyl) benzidine (TPD) is deposited onto the
indium-tin-oxide glass substrate in a vapor-depositing process to
form a uniform layer having a thickness of about 30 nm to 100 nm.
Preferably, the conducting material forms a layer having a
thickness between 40 nm to 80 nm.
[0030] Blue light-emitting material used in the concurrent
vapor-deposition process includes perylene. The blue light-emitting
material is deposited vertically onto the indium-tin-oxide glass
substrate in the vapor-deposition process to form a uniform layer
between 10 nm to 40 nm. Preferably, the deposited blue material has
a thickness between 15 nm to 30 nm. Red light-emitting material
including nile red and green light-emitting material including
quinacridone are preferably evaporated from each side at an
suitable angle simultaneously. The concentrations of the red and
the green light-emitting materials are controlled to within 0.1% to
10% (v/v) in volume ratio and preferably between 0.5% to 5%(v/v).
After the vapor-deposition process, the blue sub-pixels are formed
in the center of the pixels while the red and the green sub-pixels
are positioned on each side of the blue sub-pixel. In the
subsequent step, electron-transport material such as
tris-(8-hydroxyquinoline) aluminum (Alq3) is deposited in a
vapor-depositing process to form a uniform layer with a thickness
of about 30 nm to 100 nm. Preferably, the thickness is between 40
nm to 80 nm. magnesium (Mg) and silver (Ag) are deposited with a
tilted angle. The deposited metal functions as a negative
electrode. The deposited magnesium layer has a thickness between 10
nm to 100 nm, preferably between 30 nm to 70 nm. The deposited
silver layer has a thickness between 150 nm to 500 nm, preferably
between 200 nm to 350 nm. With the indium-tin-oxide layer
functioning as a positive electrode and the metal layer as a
negative electrode, a functional full-color organic
electro-luminescent device could be performed when a suitable
operating voltage is applied.
[0031] This invention also provides a processing station for
manufacturing the full-color organic electro-luminescent
device.
[0032] In this invention, the shadow mask is formed by a dry film
photo-resist processing. In addition, RGB sub-pixels are positioned
individually by a slant-angle depositing process so that RGB
sub-pixels can be produced in a single vapor-depositing operation.
Compared with the conventional metal-mask-shift method, in which
RGB sub-pixels are deposited in three depositing operations, the
invention has fewer processing steps and does not require accurate
mask alignment, precision shifting and mask cleaning. In brief, RGB
positioning process of this invention is simple to operate and has
a fast throughput, and hence suitable for mass production at a
lower cost.
[0033] The manufacturing station for producing electro-luminescent
device of this invention also employs an innovative design. Rather
than rotating the indium-tin-oxide glass substrate while performing
a vapor-depositing operation, the glass substrate is mounted on a
cassette and carried by a conveyer belt to various vapor-depositing
compartments for different-type depositing operations.
Consequently, the manufacturing station is capable of continuous
processing, thereby increasing overall spatial utilization. In
addition, glass substrate having a relatively large surface area
can still be vapor-deposited by the station. Since the glass
substrate is moved by a conveyer belt system, robotic arm transport
is unnecessary. Hence, cost of equipment is reduced and processing
stability is also improved.
[0034] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0036] FIGS. 1A through 1E are schematic cross-sectional views
showing the steps for producing a full-color organic
electro-luminescent device according to a Kodak's patent;
[0037] FIG. 2 is a schematic side view showing the layout of
various components of a processing station for manufacturing a
full-color organic electro-luminescent device of this
invention;
[0038] FIG. 3 is a schematic top view of a 6.times.6 pixel array
passive driven display board according to one preferred embodiment
of this invention; and
[0039] FIGS. 4A through 4G are schematic cross-sectional views
showing the progression of steps for forming a full-color organic
electro-luminescent device according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0041] FIG. 2 is a schematic side view showing a layout of
components in the processing station. The station includes a
conveyer belt 200 (not shown in FIG. 2) for moving indium-tin-oxide
glass substrates, cassettes 202 and a plurality of evaporation
source packs 204. Each evaporation source pack 204 includes at
least one evaporation source. These evaporation source packs are
able to deposit a hole-transport layer, concurrent to deposit red,
green and blue sub-pixels, then an electron-transport layer and a
metal layer. After a patterned shadow mask is formed over the
indium-tin-oxide glass substrate 212 by dry film photo-resist
processing, the indium-tin-oxide glass substrate 212 is placed in a
cassette 202 and put into area (I) of FIG. 2. The glass substrate
212 in the cassette 202 is carried by the moving conveyer belt 200
into area (II) where the evaporation source pack 204 targets the
glass substrate 212 to form a hole-transport layer. The glass
substrate 212 then moves on into area (III) where the evaporation
source pack 204 targets the glass substrate 212 to form red, green
and blue sub-pixels. The glass substrate 212 is moved to area (IV)
where the evaporation source pack 204 targets the glass substrate
212 to form an electron-transport layer. Finally, the glass
substrate 212 moves to area (V) where the evaporation source pack
204 targets the glass substrate 212 to form a metal layer. The
evaporation sources in an evaporation source pack 204 are
positioned next to each other. Each evaporation source pack 204 can
carry out vapor-deposition operation independent of others. During
the vapor-deposition process, the indium-tin-oxide glass substrate
212 remains stationary inside the cassette. Hence, no rotary motion
is imparted on the glass substrate 212. As shown in FIG. 2, the
glass substrate 212 in the cassette 202 is deposited each time on
passing in front of a rectangular opening 214. Thickness of the
vapor-deposited film depends on the parameters including deposition
rate, width of the opening 216, moving speed, locations of the
evaporation sources. These parameters are free to vary in each
vapor-depositing chamber so that deposition operations can be
optimized with identical processing period. Consequently, each
evaporation source group can carry out a different glass substrate
depositing operation concurrently. Uniformity of a deposited layer
on the glass substrate 212 in the vertical direction (vertical to
the paper, not shown) of the opening 214 depends on the positioning
of the evaporation sources and the uniformity of deposition rate
along the vertical direction. Uniformity of deposited layer can be
improved by calibrating a group of evaporation sources. The
advantages of the vapor-depositing station of this invention over a
conventional vapor-depositing station are listed out in Table 1 for
comparison. In Table 1, the symbol "O" represents "best", the
symbols ".DELTA." represent "moderate" and the symbol "X"
represents "worst".
1TABLE 1 A comparison of the vapor-depositing station in the
invention with a coventional vapor-depositing station Vapor-
Conventional vapor- depositing station acc- depositing station
ording to the invention Suitability for shadow- X O mask process
Flexibility of process- X O ing adjustments Suitability for
deposit- .DELTA. O ing different-size substrate Spatial Utilization
.DELTA. O Stability .DELTA. O Cost of the Station High Low
[0042] Compared with the indirect full-color methods such as TDK's
white light with color filter, Idemitsu Kosan's and Kodak's blue
light with color conversion medium and direct full-color method
such as an stacked device, the full-color display technique used in
this invention is a direct type, the full-color device fabricated
according to this invention has a relatively higher emission
efficiency and lower power consumption. Thus, the device is
advantageous in portable electronic products such as mobile phone,
personal data assistance (PDA) and digital camera (DC).
[0043] Red, green and blue sub-pixels in the full-color organic
electro-luminescent device of this invention are positioned on the
substrate in the same vapor-depositing operation. In addition, an
innovative dynamic manufacturing station having a continuous line
of vapor-depositing compartments is adopted for producing devices.
Therefore, the method and the manufacturing station of this
invention can be used together for the production of passive matrix
well as active matrix in a full-color organic electro-luminescent
display panel. FIG. 3 is a schematic top view of a 6.times.6
passive matrix display according to one preferred embodiment of
this invention. As shown in FIG. 3, the display board 300 can be
made of glass or plastic. Area labeled 302 shows an
indium-tin-oxide material pattern. Area labeled 304 shows the
connecting leads on the indium-tin-oxide panel for connecting with
external circuits.
[0044] FIGS. 4A through 4G are schematic cross-sectional views
showing the progression of steps for forming a full-color organic
electro-luminescent device according to this invention. FIG. 4A is
a cross-sectional view along line IV-IV' of FIG. 3. FIG. 4B is a
magnified view of the central portion of the substrate shown in
FIG. 4A to show a single pixel.
[0045] As shown in FIG. 4B, the substrate 400 can be made from
glass or plastic. Traditional photolithography and etching process
are carried out to form a desired indium-tin-oxide pattern 404.
Insulation pads 406 are formed over the pattern 404 using
photo-resist material and physic vapor depositing processes. The
insulator pad 406, preferably having a thickness of between 5 nm to
200 nm, can be a silicon oxide layer or a silicon nitride layer.
The insulation pad 206 serves two functions, including the
prevention of any current leaks from any thinner section of the
organic film layer and defining the size of light-emitting region
so that pixel size is standardized. Finally, two dry film
photo-resist processing operations are conducted to form two
different types (having different height or thickness) of shadow
masks over the insulation pads 206. The first type of shadow mask
has a height (or thickness) between 1 .mu.m to 10 .mu.m, commonly
referred to as a low shadow mask (LSM) 408. The second type of
shadow mask has a height (or thickness) between 5 .mu.m to 100
.mu.m, commonly referred to as a high shadow mask (HSM) 410.
[0046] After the patterned shadow masks are formed over the
indium-tin-oxide glass substrate 212 by dry film photo-resist
processing, the indium-tin-oxide glass substrate 212 is placed
inside a cassette 202 and put into area (I) of FIG. 2. The cassette
202 serves not only as a transportation carrier for the glass
substrate 212, but serves also as mask preventing any vapor from
depositing on electrodes near the edges of the substrate 212. As
shown in FIG. 4C, vapor deposition of hole-transport material 412
on the surface of the indium-tin-oxide glass substrate 212 to form
a hole-transport layer 414 is carried out in area (II) of FIG. 2.
The glass substrate 212 in the cassette 202 is carried by a moving
conveyer belt 200 into area (II). An evaporation source pack 204
targets the glass substrate 212 and deposits hole-transport
material vertically on the substrate 212 to form the hole-transport
layer 414. The rate of deposition of hole-transport material is
around 1 .ANG. to 3 .ANG. per second.
[0047] As shown in FIG. 4D, the high shadow mask 410 on the
substrate 212 is capable of positioning red sub-pixels 416, green
sub-pixels 418 and blue sub-pixels 420. Blue light-emitting
material can be a hole-transport or an electron-transport material.
Blue light-emitting material 420 is deposited vertically onto the
surface of the indium-tin-oxide glass substrate 212. On the other
hand, red light-emitting material 422 and green light-emitting
material 424 are deposited at an angle with the surface of the
glass substrate 212. The evaporators for the red and the green
light-emitting material are mounted on each side of the evaporator
for blue light-emitting material with the vapor beams at an angle
.theta..sub.R and .theta..sub.G respectively. In general, the
angles .theta..sub.R and .theta..sub.G are within the range from
45.degree. to 80.degree.. Utilizing the shadowing effect of the
high shadow mask 410, vapor-depositing operations are carried out
concurrently. Red and green light-emitting materials are deposited
on the right and left side of a pixel position to form a red and a
green sub-pixel. Blue light-emitting material is deposited in the
middle of the pixel position to form a blue sub-pixel. The
percentages of the red and the green light-emitting materials in
the blue light-emitting materials are about 0.5% to 5% by volume
ratio. Consequently, the film thickness in the co-deposition step
is mainly controlled by blue light-emitting material. The
deposition rate of blue light-emitting material is around 1 to 3
.ANG./s while the rate of deposition of red and green-energy-gap
material is around 0.01 to 0.3 .ANG./s. The deposition of red,
green and blue light-emitting materials is carried out in area
(III) of FIG. 2. The indium-tin-oxide glass substrate 212 is
transported by the conveyer belt 200 into area (III). Utilizing the
shadowing effect of the high shadow mask 410, red, green and blue
sub-pixels 416, 418 and 420 are concurrently formed on the
pre-defined positions.
[0048] As shown in FIG. 2, the indium-tin-oxide glass substrate 212
is moved by the conveyer belt 200 to area (IV). An evaporation
source pack 204 for electron-transport material targets the glass
substrate 212 to form an electron-transport layer 428. As shown in
FIG. 4E, an electron-transport material 426 front lands on the
surface of the indium-tin-oxide glass substrate 212 to form the
electron-transport layer 428. Deposition rate of the
electron-transport material is around 1 .ANG. to 3 .ANG. per
second.
[0049] As shown in FIG. 2, the indium-tin-oxide glass substrate 212
is moved by the conveyer belt 200 into area (V). An evaporation
source pack 204 for metal material targets the glass substrate at a
suitable angle to form a metal electrode 432. As shown in FIG. 4F,
metal material 430 is deposited onto the surface of the glass
substrate 212 at an angle .theta..sub.M from the vertical to form
the metal electrode 432. The angle .theta..sub.M ranges from
5.degree. to 60.degree.. The materials as metal electrode could be
calcium, magnesium, lithium, aluminum, silver and so on. Due to the
shadowing effect of the high shadow mask 410 and the low shadow
mask 408, the metal electrodes 432 on the substrate 212 will be
automatically isolated from each other. Hence, a full-color device
containing a plurality of pixels with each pixel comprising of red
and green sub-pixels on each side of a blue sub-pixel is
formed.
[0050] During the vapor-depositing process as shown in FIG. 2, the
indium-tin-oxide glass substrate 212 remains stationary inside the
cassette 202. Hence, no rotary motion is imparted on the glass
substrate 212. As shown in FIG. 2, the glass substrate 212 in the
cassette 202 is deposited each time on passing in front of a
rectangular opening 214. Thickness of the vapor-deposited film
depends on parameters including deposition rate, width of the
opening 216, moving speed, locations of the evaporation sources.
These parameters are free to vary in each vapor-depositing chamber
to optimize each depositing operation so that each operation is
complete within identical period. Consequently, each evaporation
source group can carry out a different glass substrate depositing
operation concurrently. Uniformity of a deposited layer on the
glass substrate 212 in the vertical direction (vertical to the
paper, not shown) of the opening 214 depends on the positioning of
the evaporation sources 204 and the uniformity of deposition rate
along the vertical direction. Uniformity of deposited layer can be
improved by calibrating a group of evaporation sources.
[0051] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *