U.S. patent application number 12/404128 was filed with the patent office on 2009-07-16 for organic light emitting display device and method of manufacturing the same.
This patent application is currently assigned to SAMSUNG MOBILE DISPLAY CO. LTD.. Invention is credited to Pil-Geun Chun, Eun-Ah Kim.
Application Number | 20090179560 12/404128 |
Document ID | / |
Family ID | 38041406 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090179560 |
Kind Code |
A1 |
Chun; Pil-Geun ; et
al. |
July 16, 2009 |
ORGANIC LIGHT EMITTING DISPLAY DEVICE AND METHOD OF MANUFACTURING
THE SAME
Abstract
A method of manufacturing an organic light emitting display
device and the organic light emitting display device which reduces
generation of dark spots by particles are disclosed. The method of
manufacturing an organic light emitting display device includes:
preparing for a substrate including a pixel circuit; forming a
pixel electrode layer on the substrate, the pixel electrode layer
including a reflection film and being electrically connected to the
pixel circuit; coating photoresist on the pixel electrode layer;
exposing and developing the photoresist using a predetermined
pattern to expose a portion of the pixel electrode layer; etching
the exposed portion of the pixel electrode layer to form a pixel
electrode electrically connected to the pixel circuit; covering the
substrate and the photoresist remaining on the pixel electrode with
an insulation film; patterning the insulation film to expose the
photoresist remaining on the pixel electrode; removing the exposed
photoresist to expose the pixel electrode; and sequentially forming
an organic light emitting layer and a facing electrode on the pixel
electrode.
Inventors: |
Chun; Pil-Geun; (Suwon-si,
KR) ; Kim; Eun-Ah; (Suwon-si, KR) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
SAMSUNG MOBILE DISPLAY CO.
LTD.
Suwon-si
KR
|
Family ID: |
38041406 |
Appl. No.: |
12/404128 |
Filed: |
March 13, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11586167 |
Oct 24, 2006 |
7510891 |
|
|
12404128 |
|
|
|
|
Current U.S.
Class: |
313/504 |
Current CPC
Class: |
H01L 51/5218 20130101;
H01L 27/3246 20130101; H01L 51/5228 20130101; H01L 2251/5315
20130101; H01L 51/0023 20130101 |
Class at
Publication: |
313/504 |
International
Class: |
H01J 1/62 20060101
H01J001/62 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 12, 2005 |
KR |
10-2005-0108287 |
Claims
1. An organic light emitting display device (OLED), comprising: a
first electrode formed over a substrate; an organic light emitting
layer comprising a portion formed over a first portion of the first
electrode; a photoresist formed over a second portion of the first
electrode, the second portion surrounding at least part of the
first portion; and a second electrode formed over the pixel
defining layer and the organic light emitting layer.
2. The OLED of claim 1, further comprising a pixel defining layer
formed over the substrate while substantially surrounding the first
electrode and the photoresist.
3. The OLED of claim 2, wherein the pixel defining layer further
comprises a portion formed over the photoresist.
4. The OLED of claim 2, wherein the organic light emitting layer
further comprises a portion interposed between the pixel defining
layer and the second electrode.
5. The OLED of claim 1, wherein the organic light emitting layer
further comprises a portion interposed between the photoresist and
the second electrode.
6. The OLED of claim 1, wherein the first electrode comprises a
reflection film.
7. The OLED of claim 6, wherein the reflection film is formed of a
metallic material.
8. The OLED of claim 7, wherein the metallic material is selected
from the group consisting of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir,
Cr, Li, and Ca.
9. The OLED of claim 1, wherein the first electrode comprises a
transparent conductor layer, a reflective conductor layer, and a
transparent conductor layer sequentially stacked over one another.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of and claims priority to
U.S. patent application Ser. No. 11/586,167, filed Oct. 24, 2006,
which claims the benefit of Korean Patent Application No.
10-2005-0108287, filed Nov. 12, 2005, in the Korean Intellectual
Property Office. The disclosures of the foregoing applications are
hereby incorporated by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of manufacturing
an organic light emitting display device and the organic light
emitting display device. More particularly, the present invention
relates to a method of manufacturing an organic light emitting
display device and the organic light emitting display device, by
which generation of dark spots by particles of a reflection film
can be reduced.
[0004] 2. Description of the Related Technology
[0005] Active matrix (AM) organic light emitting display devices
(OLED) include an array of pixels. Each pixel includes a pixel
circuit for driving an organic light emitting diode therein. The
pixel circuit is electrically connected to a scan line, a data
line, and a power supply line, and includes a thin film transistor
(TFT) and a storage capacitor. The organic light emitting diode
includes an anode, a cathode, and an organic light emitting layer
interposed therebetween. The anode is typically formed of ITO film.
The OLED further includes an encapsulating plate which covers the
array of pixels.
[0006] Top-emission AM organic light emitting display devices
typically display an image through the encapsulating plate. In the
top-emission devices, the anode may further include a reflection
film interposed between two ITO layers. However, since the
reflection film is typically formed of an easily oxidizable metal,
such as, Al, Mg, or Ag, an oxidized film is easily formed between
the reflection film and the ITO film during formation of a hole to
contact a driving thin film transistor (TFT) and the ITO film. The
oxidized film increases the resistance of the ITO film and degrades
the contact of the ITO film with the driving TFT.
[0007] In addition, the reflection film generates many particles
while being manufactured, thus causing an electrical short between
the anode and the cathode of the organic light emitting diode.
[0008] FIG. 1 is a photograph of a portion of an organic light
emitting display device in which an electrical short occurred. In
FIG. 1, a white layer which is the second from the bottom is an
anode structure formed of ITO/Ag/ITO. A black layer immediately on
the white layer is an organic emission layer (EL). A white thin
layer right on the black layer is a semi-transparent cathode. As
shown in FIG. 1, particles exist on the ITO/Ag/ITO anode structure,
shorting the anode structure and the cathode. According to an
element analysis, the particles are Ag. In other words, the
particles are produced during formation of the reflection film.
[0009] The short due to the particles produces a dark spot on the
displayed image. Accordingly, pixels including the dark spots
become inferior. The number of dark spots produced by particles of
a reflection film is at least 100 times greater than that of dark
spots produced by particles of the ITO layer.
SUMMARY OF CERTAIN INVENTIVE ASPECTS
[0010] One aspect of the invention provides a method of
manufacturing an organic light emitting display device. The method
comprises: forming a conductive layer over a substrate; forming a
photoresist layer over the conductive layer; patterning the
photoresist layer so as to expose at least a portion of the
conductive layer; etching the exposed portion of the conductive
layer through the patterned photoresist layer, thereby defining a
first electrode; forming an insulating layer over the substrate and
the patterned photoresist layer, wherein the patterned photoresist
layer remains over the first electrode; patterning the insulating
layer to expose at least a portion of the patterned photoresist
layer remaining over the first electrode; removing the at least a
portion of the patterned photoresist layer to expose at least a
portion of the first electrode; forming an organic light emitting
layer over the first electrode; and forming a second electrode over
the organic light emitting layer.
[0011] The conductive layer may comprise a reflection film. The
reflection film may be formed of a metallic material. The metallic
material may be selected from the group consisting of Ag, Mg, Al,
Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, and Ca. The conductive layer may
further comprise a transparent conductive layer. The transparent
conductive layer may be formed of a material selected from the
group consisting of ITO, IZO, In.sub.2O.sub.3, and ZnO.
[0012] Removing the at least a portion of the patterned photoresist
layer may comprise leaving another portion of the patterned
photoresist layer to remain over the first electrode, the other
portion having a top surface covered with the insulating layer. The
other portion may overlie an edge portion of the first
electrode.
[0013] Patterning the photoresist layer may comprise tapering the
photoresist layer from top to bottom. Patterning the insulating
layer may comprise exposing substantially the entire portion of the
patterned photoresist layer remaining over the first electrode.
Removing the at least a portion of the patterned photoresist layer
may comprise removing substantially the entire portion of the
patterned photoresist layer.
[0014] Another aspect of the invention provides an organic light
emitting display device made by the method described above.
[0015] Yet another aspect of the invention provides an organic
light emitting display device (OLED), comprising: a first electrode
formed over a substrate; an organic light emitting layer comprising
a portion formed over a first portion of the first electrode; a
photoresist formed over a second portion of the first electrode,
the second portion surrounding at least part of the first portion;
and a second electrode formed over the pixel defining layer and the
organic light emitting layer.
[0016] The OLED may further comprise a pixel defining layer formed
over the substrate while substantially surrounding the first
electrode and the photoresist. The pixel defining layer may further
comprise a portion formed over the photoresist. The organic light
emitting layer may further comprise a portion interposed between
the pixel defining layer and the second electrode. The organic
light emitting layer may further comprise a portion interposed
between the photoresist and the second electrode.
[0017] The first electrode may comprise a reflection film. The
reflection film may be formed of a metallic material. The metallic
material may be selected from the group consisting of Ag, Mg, Al,
Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, and Ca. The first electrode may
comprise a transparent conductor layer, a reflective conductor
layer, and a transparent conductor layer sequentially stacked over
one another.
[0018] Another aspect of the invention provides a method of
manufacturing an organic light emitting display device and the
organic light emitting display device, by which generation of dark
spots by particles can be reduced.
[0019] Another aspect of the invention provides a method of
manufacturing an organic light emitting display device, comprising:
preparing for a substrate including a pixel circuit; forming a
pixel electrode layer on the substrate, the pixel electrode layer
including a reflection film and being electrically connected to the
pixel circuit; coating photoresist on the pixel electrode layer;
exposing and developing the photoresist using a predetermined
pattern to expose a portion of the pixel electrode layer; etching
the exposed portion of the pixel electrode layer to form a pixel
electrode electrically connected to the pixel circuit; covering the
substrate and the photoresist remaining on the pixel electrode with
an insulation film; patterning the insulation film to expose the
photoresist remaining on the pixel electrode; removing the exposed
photoresist to expose the pixel electrode; and sequentially forming
an organic light emitting layer and a facing electrode on the pixel
electrode.
[0020] Yet another aspect of the invention provides a organic light
emitting display device comprising: a substrate including a pixel
circuit; a pixel electrode formed on the substrate, the pixel
electrode layer including a reflection film and being electrically
connected to the pixel circuit; photoresist with which edges of the
pixel electrode are covered; an insulation film covering the
substrate and the photoresist and exposing the pixel electrode; an
organic light emitting layer formed on at least the exposed pixel
electrode; and a facing electrode formed on the insulation film and
the organic light emitting layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The above and other aspects of the invention will become
more apparent by describing in detail exemplary embodiments thereof
with reference to the attached drawings in which:
[0022] FIG. 1 is a photograph of a cross-section of an organic
light emitting display device having a dark spot produced by
particles of a reflection film;
[0023] FIG. 2 is a schematic circuit diagram of a pixel circuit
used in an organic light emitting display device according to one
embodiment;
[0024] FIG. 3 is a circuit diagram showing the pixel circuit of
FIG. 2;
[0025] FIGS. 4 through 9 are cross-sectional views illustrating a
method of manufacturing an organic light emitting display device
according to an embodiment; and
[0026] FIGS. 10 through 13 are cross-sectional views illustrating a
method of manufacturing an organic light emitting display device
according to another embodiment.
DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS
[0027] Certain embodiments will now be described with reference to
the accompanying drawings. In the drawings, like reference numerals
indicate identical or functionally similar elements.
[0028] FIG. 2 is a schematic circuit diagram of a pixel circuit
(PC) used in an organic light emitting display device according to
one embodiment. As shown in FIG. 2, each pixel is provided with a
data line DATA, a scan line SCAN, and a Vdd power line Vdd. The Vdd
power line Vdd supplies driving power to an organic light-emitting
diode (OLED). The pixel circuit of each pixel is electrically
connected to the data line DATA, the scan line SCAN, and the Vdd
power line Vdd and controls the light emission of the OLED.
[0029] FIG. 3 is a circuit diagram showing the pixel circuit of
FIG. 2 in greater detail. The pixel circuit includes two thin film
transistors (TFTs) M1 and M2 and a single storage capacitor Cst.
Referring to FIG. 3, each pixel of the organic light emitting
display device includes at least two thin film transistors (for
example, the switching TFT M2 and the driving TFT M1), the storage
capacitor Cst, and the OLED.
[0030] The switching TFT M2 is turned on/off by a scan signal
transmitted through the scan line SCAN and delivers a data signal
transmitted from the data line DATA to the storage capacitor Cst
and the driving TFT M1. In the illustrated embodiment, the
switching TFT M2 is included as a switching device as shown in FIG.
3. In other embodiments, a switching circuit including a plurality
of TFTs and a capacitor may be included. The pixel of FIG. 2 may
further include a circuit which compensates for a threshold voltage
(Vth) value of the driving TFT M1 or a circuit which compensates
for a voltage drop of the driving power supply Vdd.
[0031] The driving TFT M1 determines the amount of current flowing
into the OLED, according to the data signal transmitted through the
switching TFT M2. The storage capacitor Cst stores the data signal
transmitted through the switching TFT M2 for one frame.
[0032] The illustrated driving TFT M1 and the switching TFT M2 are
PMOS TFTs. In other embodiments, at least one of the driving TFT M1
and the switching TFT M2 may be implemented as an NMOS TFT. In
addition, the number of TFTs and the number of capacitors are not
limited to those illustrated in FIG. 3. In other embodiments, a
greater number of TFTs and a greater number of capacitors than the
numbers illustrated in FIG. 3 may be included.
[0033] FIGS. 4 through 9 are cross-sectional views illustrating a
method of manufacturing an organic light emitting display device
according to an embodiment. Referring to FIG. 4, a driving TFT M1
is formed over a substrate 100. A passivation film 108 covers the
driving TFT M1 and the substrate 100. A pixel electrode layer 110
of an OLED is formed on the passivation film 108. Instead of the
driving TFT M1, a pixel circuit including not only the driving TFT
M1 but also a switching TFT M2 and a storage capacitor Cst as shown
in FIG. 3 may be formed over the substrate 100. The following
description will be centered on the driving TFT M1 of the pixel
circuit.
[0034] In the illustrated embodiment, the substrate 100 is formed
of glass. In other embodiments, the substrate 100 may be formed of
a plastic material or a metal, such as, SUS or Ti.
[0035] A buffer layer 101 may be further formed on an upper surface
of the substrate 100. The buffer layer 101 may be formed of an
inorganic compound and/or an organic compound, for example, SiOx
(x.gtoreq.1) and SiNx (x.gtoreq.1).
[0036] After a semiconductor active layer 102 having a
predetermined pattern is formed on the buffer layer 101, the
semiconductor active layer 102 is buried in a gate insulation layer
103. The semiconductor active layer 102 includes a source region
102b, a drain region 102c, and a channel region 102a formed between
the source and drain regions 102a and 102b. The semiconductor
active layer 102 is formed by forming an amorphous silicon film on
the buffer layer 101, crystallizing the same into a polycrystalline
silicon film, and patterning the polycrystalline silicon film. In
the embodiment of FIGS. 3 and 4, the driving TFT M1 is a PMOS type.
In other embodiments, however, the driving TFT M1 may be of NMOS
type. The semiconductor active layer 102 may be formed of an
organic semiconductor.
[0037] A gate electrode 104 overlapping with the semiconductor
active layer 102 and an interlayer insulation layer 105 burying the
gate electrode 104 are formed on the upper surface of the gate
insulation layer 103.
[0038] A contact hole is formed in the interlayer dielectric layer
105 and the gate insulation layer 103 so as to contact a source
electrode 106 and a drain electrode 107 formed on the interlayer
dielectric layer 105 with the source region 102b and the drain
region 102c, respectively. In this way, the driving TFT M1 is
formed. The passivation film 108 is formed on the top surface of
the driving TFT M1.
[0039] Next, a contact hole is formed in the passivation film 108,
and a pixel electrode layer 110 is then formed on the passivation
film 108. The pixel electrode layer 110 is contacted with the drain
electrode 107 of the driving TFT M1 via the contact hole.
[0040] The pixel electrode layer 110 may include a first layer
110a, a reflecting layer 110b, and a second layer 110c, which are
sequentially formed on the passivation film 108. The first layer
110a and the second layer 110c may be formed of a material having a
high work function, for example, a transparent conductor, such as,
ITO, IZO, In.sub.2O.sub.3, or ZnO. The reflecting layer 110b may be
formed of a metal having high light reflectance, such as, Ag, Mg,
Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of two or
more of these materials. In another embodiment, the pixel electrode
layer 110 may have a two-layered structure formed of only a
reflecting layer and a transparent conductor layer. The pixel
electrode layer 110 may have various other layer structures.
[0041] After forming the pixel electrode layer 110, a photoresist
114 is coated on the pixel electrode layer 110 to serve as a mask
when patterning the pixel electrode layer 110.
[0042] Next, the photoresist 114 is exposed to light using an
exposure mask having a predetermined pattern and developed to
expose certain portions of the pixel electrode layer 110. The
exposed portions of the pixel electrode layer 110 are etched to
form pixel electrodes 111 as shown in FIG. 5. The photoresist 114
still exists on the pixel electrodes 111. Accordingly, particles
detached from the edges of the reflecting layer 110b when etching
the pixel electrode layer 110 are attached to the surface of the
remaining photoresist 114. Hence, re-attachment of the particles to
the patterned pixel electrodes 111 is prevented. Since these
particles are removed simultaneously when the photoresist 114 is
removed as will be described later, they are prevented from being
re-attached to the pixel electrodes 111.
[0043] As shown in FIG. 6, a pixel defining film 109 is formed with
the photoresist 114 existing on the pixel electrodes 111. The pixel
defining layer 109 covers both the passivation film 108 and the
photoresist 114. The pixel defining layer 109 may be formed of an
organic insulator, an inorganic insulator, or a mixture of these
materials. In one embodiment, to achieve planarization, the pixel
defining layer 109 is formed of an organic insulator, such as,
acryl or BCB.
[0044] Next, the pixel defining layer 109 is patterned to form an
aperture 109a in the pixel defining layer 109, as shown in FIG. 7.
A predetermined portion of the photoresist 114 is exposed through
the aperture 109a. As shown in FIG. 8, the exposed portion of the
photoresist 114 is etched to expose the pixel electrodes 111.
[0045] As shown in FIG. 9, an organic light-emitting layer 112 and
a facing electrode 113 are sequentially formed over the exposed
pixel electrodes 111.
[0046] The pixel electrodes 111 serve as anode electrodes, and the
facing electrodes 113 serve as cathode electrodes. In another
embodiment, the polarity of the facing electrodes 113 may be
opposite to that of the pixel electrodes 111. In such an
embodiment, the facing electrodes 113 are anode electrodes, and the
pixel electrodes 111 are cathode electrodes.
[0047] The facing electrodes 113 may be formed of metal having a
low work function, such as, Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr,
Li, Ca, or an alloy of two or more of the foregoing. The facing
electrodes 113 may be formed of Mg, Ag, Al, etc. In one embodiment,
the facing electrode 113 may have thin semi-transparent reflection
films to transmit light after optical resonance. Bus lines or bus
electrodes may be further formed of a transparent conductor, such
as, ITO or IZO, on the facing electrodes 113 so as to lower the
sheet resistance of the facing electrodes 113.
[0048] The organic light-emitting layer 112 is interposed between
the pixel electrodes 111 and the facing electrodes 113. Voltages of
different polarities are applied to the organic light-emitting
layer 112 so that the organic light-emitting layer 112 emits
light.
[0049] The organic light-emitting layer 112 may include a small
molecular organic film or a polymer organic film. In an embodiment
in which a small molecular organic film is used, the organic
light-emitting layer 112 may be formed by stacking a hole Injection
Layer (HIL), a hole transport layer (HTL), an emission layer (EML),
an electron transport layer (ETL), and an electron injection layer
(EIL) in a single-layered or multiple layer structure. Examples of
a small molecular organic material for the organic light-emitting
layer 112 include copper phthalocyanine (CuPc), N,N-di
(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB),
tris-8-hydroxyquinoline aluminum (Alq3), etc. The small molecular
organic films may be formed by vacuum deposition. The HIL, the HTL,
the ETL, and the EIL may be common layers which are common to blue,
green, and red pixels. Hence, these common layers may cover
substantially all of the pixels of the organic light emitting
display device.
[0050] In another embodiment where a polymer organic film is used,
the organic light-emitting layer 112 may include an HTL and an EML.
In one embodiment, PEDOT is used as a HTL. A polymer organic
substance, such as poly-phenylenevinylene (PPV) or polyfluorene, is
used as an EML. The HTL and the EML may be formed by, for example,
screen printing or ink jet printing.
[0051] The organic light-emitting layer 112 is not limited to the
aforementioned structures and materials. A skilled artisan will
appreciate that the organic light-emitting layer 112 can have
various other configurations. The OLED formed in this way is
encapsulated and protected from the outside. In the organic light
emitting display device, the photoresist 114 still exists on the
edges of the pixel electrodes 111.
[0052] As shown in FIG. 10, the photoresist 114 may be patterned to
have a shape reverse to the shape of the photoresist 114 shown in
FIGS. 5 through 7. The photoresist 114 of FIG. 10 is formed using
any suitable method.
[0053] After the photoresist 114 tapering from top to bottom is
formed, a pixel defining layer 109 is formed, as shown in FIG. 12.
As shown in FIG. 12, an aperture 109a is formed in the pixel
defining layer 109. Here, the aperture 109a may taper in conformity
with the vertical tapering of the photoresist 114 of FIG. 10.
[0054] Next, the photoresist 114 exposed through the aperture 109a
is removed. Then, when an organic light-emitting layer 112 and a
facing electrode 113 are formed as described above, the structure
shown in FIG. 13 is obtained. Hence, in the present embodiment, no
photoresist exists in the pixel defining layer 109. Because the
photoresist is removed after the formation of the pixel defining
layer 109, particles of the reflecting layer 110b during etching of
the pixel electrodes 111 are not re-attached to the surface of the
pixel electrodes 111. Consequently, the number of dark spots
generated can be reduced.
[0055] Although the above-described embodiments deal with organic
light emitting display devices, they may be applied to various
types of flat panel displays other than organic light emitting
display devices.
[0056] According to the embodiments described above, a short
between a pixel electrode and a facing electrode caused by
particles produced during formation of a reflecting layer or
etching of pixel electrodes can be prevented.
[0057] While certain aspects of the invention have been shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *