(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0127657 A1
`(43) Pub. Date:
`Jul. 10, 2003
`Park
`
`US 2003O127657A1
`
`(54) ACTIVE MATRIX ORGANIC
`ELECTROLUMNESCENT DISPLAY DEVICE
`AND METHOD OF EABRICATING THE
`SAME
`(75) Inventor: Jae-Yong Park, Gyeonggi-do (KR)
`Correspondence Address:
`MORGAN LEWIS & BOCKUS LLP
`1111 PENNSYLVANIAAVENUE NW
`WASHINGTON, DC 20004 (US)
`Assignee: LG.Philips LCD Co., Ltd.
`
`(73)
`(21)
`(22)
`(30)
`
`Appl. No.:
`
`10/330,259
`
`Filed:
`
`Dec. 30, 2002
`Foreign Application Priority Data
`
`Dec. 29, 2001 (KR)....................................... 2001-88539
`
`Publication Classification
`
`(51) Int. Cl. .................................................. H01L 27/15
`
`(52) U.S. Cl. ................................................................ 257/79
`
`(57)
`
`ABSTRACT
`
`An active matrix organic electroluminescent device includes
`a Substrate, a buffer layer on the Substrate, a thin film
`transistor on the buffer layer, a passivation layer on an entire
`Surface of the Substrate covering the thin film transistor, a
`first electrode disposed on the passivation layer to contact
`the thin film transistor through a contact hole formed in the
`passivation layer, a first bank layer disposed on the first
`electrode and on the passivation layer, the first bank layer
`having a first bank opening exposing a portion of the first
`electrode, a Second bank layer disposed on the first bank
`layer to have a Second bank opening aligned with the first
`bank opening, an organic electroluminescent layer formed
`within the first bank opening to electrically contact the first
`electrode and the first bank layer, and a Second electrode
`formed on the organic electroluminescent layer and on the
`Second bank layer within the first and Second bank openings.
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 1 of 11
`
`US 2003/0127657 A1
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`FIG. I.
`Related Art
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 2 of 11
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`US 2003/0127657 A1
`
`FIG. 2
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 3 of 11
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`US 2003/0127657 A1
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`FIG. 4
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 4 of 11
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`US 2003/0127657 A1
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 5 of 11
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`US 2003/0127657 A1
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`FIG. 74
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 6 of 11
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`US 2003/0127657 A1
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 7 of 11
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`US 2003/0127657 A1
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`FIG. 7E
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 8 of 11
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`US 2003/0127657 A1
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`FIG. 7G
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 9 of 11
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`US 2003/0127657 A1
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`FIG. 7H
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`Patent Application Publication
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`Jul. 10, 2003. Sheet 10 of 11
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`US 2003/0127657 A1
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`FIG. 7
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`Patent Application Publication
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`Jul. 10, 2003 Sheet 11 of 11
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`US 2003/0127657 A1
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`FIG. 7J
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`US 2003/O127657 A1
`
`Jul. 10, 2003
`
`ACTIVE MATRIX ORGANIC
`ELECTROLUMNESCENT DISPLAY DEVICE AND
`METHOD OF FABRICATING THE SAME
`0001. The present invention claims the benefit of Korean
`Patent Application No. 2001-0088539 filed in Korea on Dec.
`29, 2001, which are hereby incorporated by reference.
`
`BACKGROUND OF THE INVENTION
`0002) 1. Field of the Invention
`0003. The present invention relates to an organic elec
`troluminescent display device, and more particularly, to an
`active matrix electroluminescent display devices and a
`method of fabricating the same.
`0004 2. Discussion of the Related Art
`0005 Currently, the need for flat panel displays having
`thin profiles, lightweight, and lower power consumption has
`increased. Accordingly, various flat panel display (FPD)
`devices Such as liquid crystal display (LCD) devices, plasma
`display panels (PDPs), field emission display (FED) devices,
`and electroluminescence display (ELD) devices are being
`developed now.
`0006 Among the many different types of FPD devices,
`the electro luminescence display (ELD) device is the only
`one that makes use of electroluminescence phenomenon in
`which light is generated when an electric field is applied to
`a fluorescent Substance. The electroluminescence display
`(ELD) devices can be classified into inorganic electrolumi
`nescence display (ELD) devices and organic electrolumi
`nescent display (ELD) devices depending on what type of
`Source excites carriers in each of the devices. The organic
`electro-luminescent display (ELD) device can display colors
`within a range of Visible wavelengths and has a high
`brightness and a low action Voltage. In addition, Since the
`organic electro-luminescence display (ELD) devices are
`Self-luminescent, they have a high contrast ratio and are
`Suitable for ultra-thin type display devices. Moreover, Since
`they have a simple manufacturing process, environmental
`contamination during manufacturing is relatively low. Fur
`thermore, the organic electro luminescence display (ELD)
`devices have a few microSeconds (us) response time So that
`they are Suitable for displaying moving images. The organic
`electroluminescence display (ELD) devices are not limited
`by their viewing angle, and are Stable under low temperature
`operating conditions. Accordingly, they can be driven with
`a relatively low voltage (between 5V and 15V), thereby
`Simplifying manufacturing and design of corresponding
`driving circuitry.
`0007 Structures of the organic electroluminescent dis
`play (ELD) devices are similar to the structures of the
`inorganic electroluminescence display (ELD) devices, but
`the light-emitting system is different from that of the inor
`ganic electroluminescence display (ELD) devices. For
`example, the organic electro luminescent display (ELD)
`devices emit light by a recombination of an electron and a
`hole, whereby they are often referred to as organic light
`emitting diodes (OLEDs). In addition, active matrix type
`Systems having a plurality of pixels arranged in a matrix
`form with a thin film transistor connected thereto has been
`widely applied to the flat panel display devices. The active
`matrix type Systems are also applied to the organic elec
`
`troluminescent display (ELD) devices and are commonly
`referred to as an active matrix organic electroluminescent
`display (ELD) device.
`0008 FIG. 1 is a cross sectional view of an active matrix
`organic electro luminescent display device according to the
`related art. In FIG. 1, a buffer layer 11 is formed on a
`Substrate 10, and a first polycrystalline Silicon layer having
`first to third portions 12a, 12b, and 12c and a second
`polycrystalline silicon layer 13a are formed on the buffer
`layer 11. The first polycrystalline silicon layer is divided into
`the first portion 12a (i.e., an active region) where impurities
`are not doped, into the Second portion 12b (i.e., a drain
`region), and into the third portion 12c (i.e., a Source region)
`where the impurities are doped. The Second polycrystalline
`Silicon layer 13.a functions as a capacitor electrode.
`0009. A gate insulation layer 14 is disposed on the active
`region 12a, and a gate electrode 15 is disposed on the gate
`insulation layer 14. A first interlayer insulator 16 is formed
`on the gate insulation layer 14 and the gate electrode 15,
`while covering the drain and Source regions 12b and 12c and
`the second polycrystalline silicon layer 13a. A power line 17
`is disposed on the first interlayer insulator 16 above the
`Second polycrystalline Silicon layer 13a. Although not
`shown, the power line 17 extends along one direction as a
`line. The power line 17, the second polycrystalline silicon
`layer 13a, and the first interlayer insulator 16 form a Storage
`capacitor. A Second interlayer insulator 18 is formed on the
`first interlayer insulator 16 to cover the power line 17.
`0010 First and second contact holes 18a and 18b pen
`etrate both the first and second interlayer insulators 16 and
`18 to expose portions of the drain region 12b and Source
`region 12c, respectively. In addition, a third contact hole 18c
`that penetrates the second interlayer insulator 18 is formed
`to expose a portion of the power line 17. A drain electrode
`19a and a source electrode 19b are formed on the second
`interlayer insulator 18, whereby the drain electrode 19a
`contacts the drain region 12b through the first contact hole
`18a, and the Source electrode 19b contacts both the Source
`region 12c and the power line 17 through the Second contact
`hole 18b and through the third contact hole 18c, respectively.
`0011 A passivation layer 20 is formed on the drain and
`Source electrodes 19a and 19b and on the exposed portions
`of the second interlayer insulator 18. The passivation layer
`20 has a fourth contact hole 20a that exposes a portion of the
`drain electrode 19a. A first electrode 21 that is made of a
`transparent conductive material is disposed on the passiva
`tion layer 20 to electrically contact the drain electrode 19a
`through the fourth contact hole 20a. A bank layer 22 is
`formed on the first electrode 21 and on the exposed portions
`of the passivation layer 20, and has an opening 22a (often
`referred to as a bank) that exposes a portion of the first
`electrode 21. An electroluminescent layer 23 is formed in the
`bank 22a of the bank layer 22. On the exposed portions of
`the bank layer 22 and on the electroluminescent layer 23, a
`Second electrode 24 is formed of an opaque metallic con
`ductive material.
`0012. In FIG. 1, the first electrode 21 is formed of the
`transparent conductive material, and the Second electrode 24
`is formed of the opaque conductive material. Accordingly,
`the light emitted from the organic electroluminescent layer
`23 is released along a bottom direction, which is commonly
`called a bottom emission-type device.
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`US 2003/O127657 A1
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`Jul. 10, 2003
`
`0013 FIG. 2 is an enlarged cross sectional view of a
`portion A of FIG. 1 according to the related art, and FIG. 3
`is a plan view of the enlarged portion A of FIGS. 1 and 2
`according to the related art. In FIGS. 2 and 3, the organic
`electroluminescent layer 23 is generally formed of a high
`molecular Substance, whereby a Solvent dissolves the high
`molecular Substance and the dissolved high molecular Sub
`stance is deposited into the bank opening 22a and on the
`bank layer 22 by an ink-jet technique. Then, the liquid high
`molecular substance on the bank layer 22 flows into the bank
`opening 22a during a heat treatment process. As a result of
`the heat treatment process, the organic electroluminescent
`layer 23 is formed in the bank opening 22a, and the Solvent
`and other impurities contained in the liquid high molecular
`Substance are removed. However, Since the bank layer 22 is
`an organic material, Such as one of the polyimide groups that
`have good interface characteristics with the high molecular
`Substance, the electroluminescent layer 23 of the high
`molecular Substance is positioned not only on the first
`electrode 21 but also on the bank layer 22 around the bank
`opening 22a, especially on Side and top Surfaces of the bank
`layer 22.
`0.014) To prevent the electroluminescent layer 23 from
`being formed on the Surfaces of the bank layer 22, a plasma
`treatment may be conducted on the electroluminescent layer
`23 of high molecular Substance. However, the plasma treat
`ment causes the electroluminescent layer 23 to have poor
`interface characteristics with the first electrode 21, thereby
`preventing adequate bonding to the first electrode 2. Accord
`ingly, the electroluminescent layer 23 delaminates due to
`thermal Stresses when the electroluminescent layer 23 is
`operated for a long period of time, thereby significantly
`reducing its operational life span.
`0.015. In addition, since the electroluminescent layer 23 is
`disposed on inclined Side and top Surfaces of the bank layer
`22, as denoted by portions C in FIGS. 2 and 3, the light
`emitted from the portions C of the electroluminescent layer
`23 has abnormally paths, as compared to the light emitted
`from a portion B where the electroluminescent layer 23 is
`disposed on the first electrode 21. The light generated in the
`portions C provides different spectral distributions of red,
`green, and blue light, whereby the red, green, and blue colors
`are refracted and disperse. Accordingly, it is difficult for the
`organic electroluminescent display devices shown in FIGS.
`1, 2, and 3 to achieve white balance and to obtain a gray
`level display.
`
`SUMMARY OF THE INVENTION
`0016. Accordingly, the present invention is directed to an
`active matrix organic electroluminescent display device and
`method of fabricating the same that substantially obviates
`one or more of problems due to limitations and disadvan
`tages of the related art.
`0.017. An object of the present invention is to provide an
`active matrix organic electroluminescent display device
`having Stable Structure elements and prolonged operational
`life Span.
`0.018. Another object of the present invention is to pro
`vide a method of fabricating an active matrix organic
`electroluminescent display device having prolonged opera
`tional life and high resolution and picture quality.
`
`0019. Another object of the present invention is to pro
`vide an active matrix organic electroluminescent display
`device having high resolution and picture quality.
`0020 Additional features and advantages of the inven
`tion will be set forth in the description which follows, and
`in part will be apparent from the description, or may be
`learned by practice of the invention. These and other advan
`tages 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.
`0021. To achieve these and other advantages and in
`accordance with the purpose of the present invention, as
`embodied and broadly described, an active matrix organic
`electroluminescent device includes a Substrate, a buffer layer
`on the Substrate, a thin film transistor on the buffer layer, a
`passivation layer on an entire Surface of the Substrate
`covering the thin film transistor, a first electrode disposed on
`the passivation layer to contact the thin film transistor
`through a contact hole formed in the passivation layer, a first
`bank layer disposed on the first electrode and on the passi
`Vation layer, the first bank layer having a first bank opening
`exposing a portion of the first electrode, a Second bank layer
`disposed on the first bank layer to have a Second bank
`opening aligned with the first bank opening, an organic
`electroluminescent layer formed within the first bank open
`ing to electrically contact the first electrode and the first bank
`layer, and a Second electrode formed on the organic elec
`troluminescent layer and on the Second bank layer within the
`first and Second bank openings.
`0022. In another aspect, a method of fabricating an active
`matrix organic electroluminescent device includes forming a
`buffer layer on a Substrate, forming a thin film transistor on
`the buffer layer, forming a passivation layer over the Sub
`Strate to cover the thin film transistor, forming a first
`electrode on the passivation layer to electrically contact the
`thin film transistor through a contact hole formed in the
`passivation layer, forming a first bank layer on the first
`electrode and on the passivation layer, forming a Second
`bank layer on the first bank layer, forming a bank opening
`through the first and Second bank layers to expose a portion
`of the first electrode, forming an organic electroluminescent
`layer within the bank opening to contact the first electrode
`and the first bank layer, and forming a Second electrode on
`the organic electroluminescent layer and on the Second bank
`layer.
`0023. In another aspect, an active matrix organic elec
`troluminescent device includes a Substrate, a buffer layer on
`the Substrate, a thin film transistor on the buffer layer, a gate
`line on the buffer layer, a first insulating layer on the thin
`film transistor- and the gate line, a power line on the first
`insulating layer over the gate line, a Second insulating layer
`on the first insulating layer and the power line, a first
`electrode disposed on the Second insulating layer, the first
`electrode electrically contacts the thin film transistor through
`a first hole formed in the first and Second insulating layers
`and electrically contacts the power line through a Second
`hole formed in the Second insulating layer, a passivation
`layer disposed on an entire Surface of the Substrate covering
`the Second interlayer insulating layer and the thin film
`transistor, a Second electrode disposed on the passivation
`layer to contact the thin film transistor through a third
`contact hole formed in the passivation layer, a first bank
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`layer disposed on the Second electrode and on the passiva
`tion layer, the first bank layer having a first bank opening
`exposing a portion of the Second electrode, a Second bank
`layer disposed on the first bank layer to have a Second bank
`opening aligned with the first bank opening, an organic
`electroluminescent layer disposed within the first bank open
`ing to electrically contact the Second electrode and the first
`bank layer, and a third electrode disposed on the organic
`electroluminescent layer and on the Second bank layer
`within the first and Second bank openings.
`0024.
`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 DRAWING
`0.025 The accompanying drawings, which are included
`to provide a further understanding of the invention and are
`incorporated in and constitute a part of this specification,
`illustrate embodiments of the invention and together with
`the description Serve to explain the principles of the inven
`tion. In the drawings:
`0.026
`FIG. 1 is a cross sectional view of an active matrix
`organic electro luminescent display device according to the
`related art,
`0.027
`FIG. 2 is an enlarged cross sectional view of a
`portion A of FIG. 1 according to the related art;
`0028 FIG. 3 is a plan view of the enlarged portion A of
`FIGS. 1 and 2 according to the related art;
`0029 FIG. 4 is a cross sectional view of an exemplary
`active matrix organic electro luminescent display device
`according to the present invention;
`0030 FIG. 5 is an enlarged cross sectional view of an
`exemplary portion D of FIG. 4 according to the present
`invention;
`0.031
`FIG. 6 is a plan view of the enlarged portion D of
`FIGS. 4 and 5 according to the present invention; and
`0032 FIGS. 7A to 7J are cross sectional views of an
`exemplary fabricating process of an active matrix organic
`electro luminescent display device of FIG. 4 according to
`the present invention.
`
`DETAILED DESCRIPTION OF THE
`ILLUSTRATED EMBODIMENTS
`Reference will now be made in detail to an embodi
`0.033
`ment of the present invention, example of which is illus
`trated in the accompanying drawings.
`0034 FIG. 4 is a cross sectional view of an exemplary
`active matrix organic electroluminescent display device
`according to the present invention. In FIG. 4, a buffer layer
`110 may be formed on a substrate 100, and a first polycrys
`talline Silicon layer having first, Second, and third portions
`121, 122, and 123 and a Second polycrystalline Silicon layer
`125 may be formed on the buffer layer 110. The first
`polycrystalline silicon layer may be divided into the first
`portion 121 (i.e., an active region) where impurities are not
`doped, the Second portion 122 (i.e., a drain region), and the
`third portion 123 (i.e., a Source region) where the impurities,
`
`Such as ions, are doped. In addition, the Second polycrys
`talline Silicon layer 125 may function as a capacitor elec
`trode.
`0035) Agate insulation layer 130 may be disposed on the
`active region 121, and a gate electrode 131 may be disposed
`on the gate insulation layer 130. A first interlayer insulator
`140 may be formed on the gate insulation layer 130 and on
`the gate electrode 131 to cover the drain and Source regions
`122 and 123 and the second polycrystalline silicon layer
`125. A power line 151 may be disposed on the first interlayer
`insulator 140 above the second polycrystalline silicon layer
`125 (i.e., the capacitor electrode). Although not shown, the
`power line 151 may extend as a line along one direction. The
`power line 151 and the second polycrystalline silicon layer
`125 may form a Storage capacitor with the first interlayer
`insulator 140 interposed therebetween. A second interlayer
`insulator 160 may be formed on the first interlayer insulator
`140 to cover the power line 151.
`0036 First and second contact holes 161 and 162 may be
`formed to penetrate both the first and Second interlayer
`insulators 140 and 160 to expose portions of the drain region
`122 and Source region 123. In addition, a third contact hole
`163 may be formed to penetrate the second interlayer
`insulator 160 to expose a portion of the power line 151. A
`drain electrode 171 and source electrode 172 may be formed
`on the second interlayer insulator 160, whereby the drain
`electrode 171 contacts the drain region 122 through the first
`contact hole 161, and the Source electrode 172 contacts both
`the source region 123 and the power line 151 through the
`second contact hole 162 and through the third contact hole
`163, respectively. A passivation layer 180 may be formed on
`the drain and source electrodes 171 and 172 and on exposed
`portions of the second interlayer insulator 160, whereby the
`passivation layer 180 may have a planar upper Surface. In
`addition, the passivation layer 180 may have a fourth contact
`hole 181 that exposes a portion of the drain electrode 171.
`Then, a first electrode 190 made of a transparent conductive
`material may be disposed on the planar upper Surface of the
`passivation layer 180 and may electrically contact the drain
`electrode 171 through the fourth contact hole 181. The
`transparent conductive material for the first electrode 190
`may include indium-tin-oxide (ITO) or indium-zinc-oxide
`(IZO).
`0037. In FIG.4, first and second bank layers 200 and 210
`may be formed on the first electrode 190 and on the exposed
`portions of the passivation layer 180, whereby the first and
`second bank layers 200 and 210 may have a bank opening
`212 (often referred to as a bank) that exposes a portion of the
`first electrode 190. An organic electroluminescent layer 220
`may be formed within the bank opening 212 of the first bank
`layer 200, especially on the first electrode 190. Then, a
`second electrode 230 may be formed over an entire surface
`of the substrate 100 to overlap the second bank layer 210 and
`the organic electroluminescent layer 220. The Second elec
`trode 230 may include opaque metallic materials including
`aluminum (Al), aluminum alloys (e.g., AlNd), and calcium
`(Ca).
`0038 FIG. 5 is an enlarged cross sectional view of an
`exemplary portion D of FIG. 4 according to the present
`invention, and FIG. 6 is a plan view of the enlarged portion
`D of FIGS. 4 and 5 according to the present invention. In
`FIGS. 5 and 6, the organic electroluminescent layer 220
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`may be formed only within the bank opening 212. Accord
`ingly, the organic electroluminescent layer 220 is only on the
`first electrode 190 and does not overlap the second bank
`layer 210. Although the first and second bank layers 200 and
`210 may be formed of organic materials, the first bank layer
`200 is formed of a material having hydrophilic properties
`and the second bank layer 210 is formed of a material having
`hydrophobic properties. The hydrophilic properties of the
`first bank layer 200 accelerates adhesive strength with the
`organic electroluminescent layer 220, and the hydrophobic
`properties of the second bank layer 210 decelerates adhesive
`Strength with the organic electroluminescent layer 220. A
`high molecular Substance may be dissolved in a Solvent and
`deposited onto top and inclined side Surfaces of the Second
`bank layer 210 when forming the organic electroluminescent
`layer 220. Accordingly, the dissolved high molecular Sub
`stance may easily flow downward into the bank opening 212
`Since it does not have good adhesive properties with the
`hydrophobic second bank layer 210. In addition, a thickness
`of the first bank layer 200 may be larger than a thickness of
`the organic electroluminescent layer 220 So that the organic
`electroluminescent layer 220 does not contact the Second
`bank layer 200. For example, the first bank layer 200 may
`have a thickness twice as much as a thickness of the organic
`electroluminescent layer 220, and the second bank layer 210
`may also have a thickness of more than 0.5 micrometers
`
`Since the organic electroluminescent layer 220 is
`0.039
`disposed only within the bank opening 212 and not on the
`top or side surfaces of the bank layers 200 and 210, the
`delamination phenomenon of the organic electroluminescent
`layer 220 may be prevented. In addition, Since the organic
`electroluminescent layer 220 adheres much more to the
`hydrophilic first bank layer 200, the organic electrolumines
`cent layer 220 can be much more Stable and the operational
`life span of the organic electroluminescent layer 220 may be
`prolonged. Furthermore, when comparing FIGS. 5 and 6 to
`FIGS. 2 and 3, the portions C in FIGS. 2 and 3 is decreased
`to become portions F of FIGS. 5 and 6 where the electrolu
`minescent layer 220 contacts only the first bank layer 200.
`Thus, an essential light-emitting area E may become larger,
`thereby improving resolution and image quality.
`0040 FIGS. 7A to 7J are cross sectional views of an
`exemplary fabricating process of an active matrix organic
`electro luminescent display device of FIG. 4 according to
`the present invention. Many of the layer patterns shown in
`FIGS. 7A to 7J may be formed through photolithographic
`processes using photoresist (PR) coatings, aligning, and
`exposure and developing StepS using a mask. In FIG. 7A,
`after a buffer layer 110 is formed on an entire surface of a
`substrate 100, first and second silicon layers 126 and 127 of
`polycrystalline may be formed on the buffer layer 110
`through a first mask process, wherein the first and Second
`polycrystalline silicon layers 126 and 127 may have island
`shapes.
`0041. In FIG. 7B, an insulator of silicon nitride or silicon
`oxide and a conductive material of metal may be sequen
`tially deposited onto the first polycrystalline Silicon layer
`126, and then patterned using a Second mask. Accordingly,
`a gate insulation layer 130 and a gate electrode 131 may be
`Sequentially formed on the first polycrystalline Silicon layer
`126. Then, p-type or n-type ion impurities may be doped on
`exposed portions of the first and Second polycrystalline
`
`Silicon layerS 126 and 127. During the doping process, Since
`the gate electrode 131 acts as a mask, the first polycrystalline
`silicon layer 126 may be divided into an active region 121
`where the impurities are not doped, and drain and Source
`regions 123 and 123 where the impurities are doped. Fur
`thermore, the Second polycrystalline Silicon layer 127 upon
`which the impurities are fully doped may function as a
`capacitor electrode 125.
`0042. In FIG.7C, a first interlayer insulator 140 may be
`formed on an entire surface of the buffer layer 110 to cover
`the gate electrode 131, the drain and Source regions 122 and
`123, and the capacitor electrode 125. Then, a power line 151
`made of a metal material may be formed through a third
`mask process on the first interlayer insulator 140 to overlap
`the capacitor electrode 125. Since the power line 151 may be
`formed above the capacitor electrode 125, a Storage capaci
`tor may be formed with the capacitor electrode 125 and the
`interposed first interlayer insulator 140.
`0043. In FIG. 7D, a second interlayer insulator 160 may
`be formed on the firs