Patent Application
20080157099
This application claims the benefit of Korean Patent Application No. 2006-138321, filed Dec. 29, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
Aspects of the present invention relate to an organic light emitting display and a fabricating method thereof, and more particularly, to an organic light emitting display and a fabricating method thereof capable of precisely controlling the position of crystallization of an amorphous silicon and forming an active layer (thin film transistor) by forming an alignment mark on a region of a substrate.
2. Description of the Related Art
Generally, an organic light emitting diode is an apparatus in which an electron and a hole are bound in a fluorescent and/or phosphorescent organic compound to thereby emit light by injecting the hole from an anode and injecting the electron from a cathode into a light emitting layer.
As shown in
A passive matrix driving method and an active matrix driving method may be used to drive the organic light emitting diode. The passive matrix driving method has advantages that the manufacturing process is simple and the investment cost is low. The passive matrix driving method uses an anode and a cathode that cross in an orthogonal direction from which lines are selected and driven; however the passive matrix driving method is disadvantageous in that the current consumption is too high when used to drive a large size display. The active matrix driving method has advantages in that the current consumption is low, the display quality and life of the display is good, and the active matrix driving method may be applied to a medium to large size display by forming an active element and a storage capacitor at each pixel.
The fabricating method of the organic light emitting display includes an operation of crystallizing the amorphous silicon, an operation of fabricating the active layer (thin film transistor), and an operation of fabricating the organic light emitting diode. There is an encapsulation operation, a module assembly operation, and the like; however, the explanation of such operations will be omitted.
The operation of crystallizing the amorphous silicon comprises a substrate cleaning operation, a buffer layer forming operation, an amorphous silicon vapor depositing operation, a polysilicon forming operation, and the like.
The operation of fabricating the active layer comprises an operation of pattering the polysilicon, a gate insulating layer forming operation, a gate patterning operation, an ion injecting/activating operation, an interlayer dielectric layer forming operation, a contact forming operation, source/drain patterning operation, and the like. An insulating layer and via forming operation, an ITO forming operation, and a pixel definition layer forming operation are further executed.
The organic light emitting diode fabricating operation comprises a cleaning operation, a pretreatment operation, an organic light emitting diode vapor depositing operation, a cathode vapor depositing operation, and the like.
The forming positions of the amorphous silicon crystallizing operation and the active layer (thin film transistor) fabricating operation are precisely controlled so that a characteristic dispersion of the diode becomes minimal. For example, in the amorphous silicon crystallizing operation, it is preferable that the forming size and direction, etc. of the polysilicon are precisely controlled so that a grain boundary of the polysilicon has a maximum size and uniform directional property. In the active layer (thin film transistor) fabricating operation, it is preferable that the source/drain/gate are controlled and formed (patterned) so that they are positioned in the region and direction having an optimal grain boundary. Further, even in the gate electrode forming operation, it is preferable to form the gate electrode with respect to the size and direction of the polysilicon as described above.
However, the crystallization technology in consideration of position and direction during the crystallization process, which is converting the amorphous silicon to the polysilicon, and the technology in consideration of the position and direction during the active layer forming process are not well developed. The organic light emitting display, unlike a liquid crystal display, generally forms the active layer (thin film transistor) after the amorphous silicon is crystallized to form the polysilicon; however, any technology optimizing the position of the polysilicon and active layer (thin film transistor) is not well developed.
Therefore, the properties of the manufactured thin film transistor, such as threshold voltage, S-factor, off current, and mobility, are not uniform among the formed thin film transistors, and thus there is a problem that the luminance of the organic light emitting diode driven by the controlled current is also not uniform due to the lack of precision in forming the polysilicon and the active layer (thin film transistor).
Aspects of the present invention overcome the above-described and/or other problems, and an aspect of the present invention is to provide an organic light emitting display and a fabricating method thereof capable of controlling the position of crystallization of an amorphous silicon precisely and forming an active layer (thin film transistor) by forming an alignment mark on a certain region of a substrate.
An organic light emitting display according to aspects of the present invention includes a substrate having a display region and a non-display region; a buffer layer formed on the display region and the non-display region in which a catalytic metal is present; an alignment mark formed on one of the buffer layer and the substrate in the non-display region of the substrate; an active layer formed on the buffer layer by an SGS crystallization method corresponding to the display region of the substrate; a gate insulating layer formed on the alignment mark and the active layer; a gate electrode formed on the gate insulating layer corresponding to the active layer; an interlayer dielectric layer formed on the gate insulating layer; a source/drain electrode formed on the interlayer dielectric layer and electrically coupled to the active layer; an insulating layer formed on the source/drain electrode; and an organic light emitting diode formed on the insulating layer and electrically coupled to the source/drain electrode.
The volume density of the catalytic metal present in the buffer layer may be less than 2.0×1018 atoms/cm3. The catalytic metal may also remain in the alignment mark and the active layer. The volume density of the catalytic metal, which remains in the alignment mark and the active layer, may be 21.0E16 to 1.0E20 atoms/cm3. The catalytic metal is selected from the group comprising Ni, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Mo, Tr, Ru, Rh, Cd, Pt, or combinations thereof.
The active layer is the polysilicon formed by the SGS crystallization method, and no grain boundary or at least one grain boundary may be in the polysilicon.
The alignment mark may be formed on the buffer layer. The alignment mark may be formed underneath the buffer layer. The alignment mark may be made of any one selected from the group consisting of a conductor, an insulator, an amorphous silicon, a microsilicon and a polysilicon. The thickness of the alignment mark may be 100 to 1000 Å. The shape of the alignment mark may be any one selected from a triangle shape, a square shape, a rhombus shape, a pentagon shape, a cross shape, and combinations thereof. The cross-sectional area of the alignment mark may be 100 to 900 μm2. The width of the alignment mark may be 1 to 20 μm.
The thin film transistor comprises the active layer, the gate insulating layer, the gate electrode, the interlayer dielectric layer and the source/drain, and the average of S-factor of the thin film transistor may be 0.44 V/dev and the standard deviation may be 0.01 V/dev.
The thin film transistor comprises the active layer, the gate insulating layer, the gate electrode, the interlayer dielectric layer and the source/drain, and the average of the off current of the thin film transistor may be 1.20E-12 A/μm, and the standard deviation may be 4.10E-13 A/μm.
The display region may be formed at the center of the substrate, and the non-display region may be formed about the periphery of the display region. The substrate may be any one selected from a glass, a plastic, a stainless steel, and a nano complex composition.
The interlayer dielectric layer may further be formed on the gate insulating layer corresponding to the alignment mark. The insulating layer may further be formed on the interlayer dielectric layer corresponding to the alignment mark. The insulating layer may be consisted of a protective layer and a planarization layer, and it may be formed on the region corresponding to the alignment mark.
A fabricating method of the organic light emitting display according to aspects of the present invention includes an operation of preparing a substrate which is provided with a non-display region formed about a periphery of the display region; an operation of forming a buffer layer on the display and non-display regions; an operation of forming an alignment mark on the non-display region; an operation of depositing an amorphous silicon on the buffer layer; an operation of forming a capping layer on the amorphous silicon; an operation of converting the amorphous silicon to a polysilicon by diffusing the catalytic metal throughout the amorphous silicon and performing heat treatment; an operation of forming an active layer by using the polysilicon; and an operation of forming an organic light emitting diode that electrically coupled to the active layer.
The operation of forming the capping layer includes an operation of forming a diffusion preventing layer having at least one opening for position control at a position spaced apart from the alignment mark, and an operation of forming a diffusion layer that covers the opening for position control and the diffusion preventing layer.
The operation of forming the active layer may form the active layer at a position spaced apart from the alignment mark.
The catalytic metal used in the polysilicon forming operation may be selected from the group comprising Ni, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Mo, Tr, Ru, Rh, Cd, Pt, and combinations thereof. The catalytic metal used in the polysilicon forming operation may remain in the buffer layer. The volume density of the catalytic metal that remains in the buffer layer may be 2.0×1018 atoms/cm3 and below. The catalytic metal used in the polysilicon forming operation may remain in any one of the alignment mark and the buffer layer. The volume density of the catalytic metal that remains in the alignment mark and the active layer may be 1.0×1016 to 10×1020 atoms3.
The heat treatment temperature applied to the polysilicon forming operation may be 400 to 700° C.
After the operation of forming the active layer, an operation of removing the amorphous silicon except for the active layer may further be included.
The alignment mark forming operation may form the alignment mark on the buffer layer. The alignment mark forming operation may form the alignment mark underneath the buffer layer. In the alignment mark forming operation, the alignment mark may be made of any one selected from the group consisting of a conductor, an insulator, an amorphous silicon, a microsilicon and a polysilicon. In the alignment mark forming operation, the thickness of the alignment mark may be 100 to 1000 Å. In the alignment mark forming operation, the plane shape of the alignment mark may be a triangle shape, a square shape, a rhombus shape, a pentagon shape and a cross shape. In the alignment mark forming operation, the cross-sectional area of the alignment mark may be 100 to 900 μm2. In the alignment mark forming operation, the width of the alignment mark may be 1 to 20 μm.
Therefore, an organic light emitting display and a fabricating method thereof may form the polysilicon and the active layer (thin film transistor) at an optimal position by using the alignment mark, as the alignment mark is formed on the non-display region of the substrate.
That is, the characteristic dispersion between the diodes may be considerably improved, by forming the polysilicon having the grain boundary of optimal size, direction, and position by use of the alignment mark, and by forming the active layer (thin film transistor) of optimal position by use of the polysilicon.
For example, the thin film transistor formed by the aforementioned method may have the average S-factor of 0.44 V/dev with a standard deviation of 0.01 V/dev. Also, the thin film transistor may have the average off current of 1.20E-12 A/μm with a standard deviation of 4.10E-13 A/μm.
The organic light emitting diodes, which are electrically coupled to the thin film transistor formed by the aforementioned method, have the uniform luminance, even if the size of the panel is enlarged.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
a to 3f are enlarged views illustrating various shapes of the alignment mark of
a and 5b are cross-sectional views illustrating the relation between the alignment mark and the pixel circuit.
a to 7i are cross-sectional views illustrating the fabricating method of the organic light emitting display according to aspects of the present invention.
Reference will now be made in detail to the present embodiments or aspects of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. Hereinafter, aspects of the present invention will be described more specifically with reference to the accompanying drawings, so that a person ordinarily skilled in the art will understand the different aspects of the present invention without difficulties from the explanation, as follows.
Referring
The substrate 110 may be formed into the display region 111 in a rectangular shape, and the non-display region 112 in a hollow-rectangular band shape surrounding the display region 111. However, the substrate 110 is not limited thereto such that the display region 111 and the non-display region 112 may be formed differently. For example, the display region 111 may comprise square regions between which the non-display region 112 extends. Or, the display region 111 and the non-display region 112 may be formed in another shape, such as triangles. In the display region 111, a plurality of data lines (D1 to Dm) may be formed in a first direction, and a plurality of scan lines (S1 to Sn) and emission control lines (E1 to En) may be formed in a second direction. The first direction may be vertical with respect to an image to be displayed, and the second direction may be disposed to cross the first direction or be horizontal with respect to the image to be displayed; however, the first and second directions are not limited thereto. The emission control lines (E1 to En) as well as light-emission bar control lines (E1B to EnB) may further be formed in the display region 111.
The pixel region 120 may be formed in the intersection region of the data lines (D1 to Dm), the scan lines (S1 to Sn), and the emission control lines (E1 to En) in the display region 111 of the substrate 110. The pixel region 120 may be formed by a transistor, a storage capacitor, and an organic light emitting diode. The pixel region 120 will be described in greater detail below.
At least one alignment mark 130 may be formed in the non-display region 112 of the substrate 110. The alignment mark 130 is used to control the position of the formation of the amorphous silicon during the crystallization process thereof, and the alignment mark 130 is used to control the position of the formation of the active layer (thin film transistor) at an optimal location. The alignment mark 130 may also be used to control the position of the formation of the gate electrode, the data lines, the scan lines, the emission control lines, and the organic light emitting diodes when each are formed. And, the alignment mark 130 may be formed with any one selected from the group consisting of a conductor, an insulator, an amorphous silicon, a microsilicon and a polysilicon; however, the material from which the alignment mark 130 is formed is not limited thereto. The alignment mark 130 may be formed up, down, left and right symmetrical shape or asymmetrical shape, and the number of it may be 1 to 20. However, the position and number of the alignment mark 130 is not limited thereto.
The data driver 140 provides data signals to the pixel region 120 of the display region 111 on the substrate 110 via a plurality of the data lines (D1, . . . , Dm). The scan driver 150 provides scan signals to the pixel region 120 of the display region 111 on the substrate 110 via a plurality of the scan lines (S1, . . . , Sn) in sequence. The emission driver 160 provides emission control signals to the pixel region 120 of the display region 111 of the substrate 110 via a plurality of the emission control lines (E1, . . . , En).
The data driver 140, the scan driver 150, and the emission driver 160 may be formed on the substrate 110. For example, the data, scan, and emission drivers 140, 150, and 160 may be formed on the non-display region 112 on the substrate 110 as an integrated circuit or as individual integrated circuits. Furthermore, the data, scan, and emission drivers 140, 150, and 160 may be formed on an identical layer, on which the transistors of the data lines (D1, . . . , Dm), the scan lines (S1, . . . , Sn), the emission control lines (E1, . . . , En), and the pixel region 120 are formed. The data, scan, and emission drivers 140, 150, and 160 may be formed on a separate layer, and the separate layer may be coupled to the substrate 110. Moreover, the data, scan, and emission drivers 140, 150, and 160 may be configured in the form of any one selected from a TCP (Tape Carrier Package), an FPC (Flexible Printed Circuit), a TAB (Tape Automatic Bonding), a COG (Chip On Glass), and equivalents thereof, and the shapes and the positions of the drivers according to aspects of the present invention are not limited.
Referring to
It is preferable that the cross-sectional area of the alignment mark 130 is formed to be 100 to 900 μm2. That is, if the cross-sectional area of the alignment mark 130 is 100 μm2 or below then it is difficult to see the alignment mark 130 under a microscope, and if the cross-sectional area of the alignment mark 130 is 900 μm2 or above then it is difficult for the alignment mark 130 to be used to control the position during the crystallization process or the active layer forming process. As used herein, cross-sectional area of the alignment mark 130 refers the area of the alignment mark 130 with reference to a plane as defined by the substrate 110 or the buffer 120.
Further, since the shape of the alignment mark 130 can be one of various shapes, it is preferable that the width of the alignment mark 130 is 20 μm or below. That is, when the width of the alignment mark 130 is 20 μm or above, the tolerance for defining the position of the alignment mark 130 is too great so that the features of the alignment mark 130 are lost. The range of 1 to 20 μm is sufficient when it can be seen through the microscope.
Referring to
In the pixel circuit as shown in
a and 5b are cross-sectional views of the organic light emitting display illustrating the relation between the alignment mark and the pixel circuit. As shown in
The substrate 210 is generally flat and has flat upper and lower surfaces. The thickness of the substrate 210 between the upper and lower surfaces is approximately 0.05 to 1 mm. When the thickness of the substrate 210 is 0.05 mm and below, the substrate 210 is vulnerable to the damage from cleaning, etching, and heat treatment processes and from external force. If the thickness of the substrate 210 is 1 mm and above, such thickness increases a thickness of the display device. Further, the substrate 210 may be any one selected from a glass, a plastic, a stainless steel, a nanocomplex composition and equivalents thereof; however, the substrate 210 is not limited thereto. The substrate 210 is classified into the display region 211 and the non-display region 212. As described above, the pixel region including the active layer 240 and/or the organic light emitting diode 300 is formed in the display region 211 of the substrate 210, and the alignment mark 230 and the various drivers (140, 150, 160) may formed in the non-display region 212.
The buffer layer 220, disposed on the upper layer of the substrate 210, may be formed in the display region 211 and the non-display region 212. The buffer layer 220 prevents H2O, H2, O2, and the like from penetrating through the substrate and affecting the alignment mark 230 and the active layer 240. The buffer layer 220 may be formed of at least any one selected from the group consisting of silicon oxide film (SiO2), silicon nitride film (Si3N4), inorganic film, and equivalents thereof; however, the buffer layer 220 is not limited thereto. The buffer layer 220 may be omitted.
Here, the catalytic metal from the crystallization process may remain in the buffer layer 220. The catalytic metal may be selected from the group comprising of Ni, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Mo, Tr, Ru, Rh, Cd, Pt, and equivalents and combinations thereof; however, the catalytic metal is not limited thereto. For example, the catalytic metal may be any metal that promotes or catalyzes the crystallization of the amorphous silicon. The catalytic metal, as described below, is formed during the process that crystallizes the amorphous silicon into the polysilicon. It is preferable that the volume density of the catalytic metal is controlled to be 2.0×1018 atoms/cm3 and below. That is, when the volume density of the catalytic metal is 2.0×1018 atoms/cm3 and above, a leakage current may flow. The electrical characteristics of the OLED 200 are improved as the volume density of the catalytic metal is reduced.
The alignment mark 230 may be formed on the upper surface of the buffer layer 220 in the non-display region 212 of the substrate 210. The alignment mark 230 may be any one selected from the group consisting of a conductor, an insulator, an amorphous silicon, a microsilicon, a polysilicon, and equivalents thereof; however alignment mark 230 is not limited thereto. It is preferable that the thickness of the alignment mark 230 is 100 to 1000 Å. When the thickness of the alignment mark 230 is less than about 100 Å, then the alignment mark 230 is too transparent to be functional with current technology. And, when the thickness of the alignment mark 230 is greater than about 1000 Å, then the alignment mark 230 may be unnecessarily thick. Even though the alignment mark 230 is shown as formed on the buffer layer 220 as in
The plane shape of the alignment mark 230, 230a may be a shape selected from a triangle shape, a square shape, a rhombus shape, a pentagon shape, a cross shape, a “┤” shape, and equivalents thereof, or a combination of such shapes. However, the plane shape of the alignment mark 230, 230a is not limited thereto (see
It is preferable that the cross-sectional area of the alignment mark 230, 230a is formed to be 100 to 900 μm2. That is, if the cross-sectional area of the alignment mark 230, 230a is less than about 100 μm2 then the alignment mark 230, 230a is difficult to see the alignment mark 230, 230a under a microscope. If the cross-sectional area of the alignment mark 230, 230a is 900 μm2 or above, the alignment mark 230, 230a becomes difficult to use it as an alignment mark 230, 230a. As used herein, cross-sectional area of the alignment mark 230, 230a refers the area of the alignment mark 230, 230a with reference to a plane as defined by the substrate 210 or the buffer 220.
As the shape of the alignment mark 230, 230a can be any various shape, it is preferable that the width of the alignment mark 230, 230a is approximately less than 20 μm. That is, when the width of the alignment mark 230, 230a is greater than approximately 20 μm, the tolerances associated with defining the position of the alignment mark 230, 230a are too great such that the features of the alignment mark 230, 230a are lost. The range of 1 to 20 μm is sufficient when the alignment mark 230, 230a can be seen through the microscope.
The catalytic metal may remain in the alignment mark 230, 230a. In particular, the catalytic metal may remain in the alignment mark 230, 230a when the alignment mark 230, 230a is an insulator, an amorphous silicon, a microsilicon, and an organic material.
As described above, the catalytic metal may be selected from the group comprising Ni, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Mo, Tr, Ru, Rh, Cd, Pt and equivalents and combinations thereof; however, the catalytic metal is not limited thereto. As described below, the catalytic metal is formed during the crystallization process of converting the amorphous silicon into the polysilicon.
Continuing with reference to both
When the thin film transistor is a polysilicon thin film transistor, the polysilicon thin film transistor may be formed by any one selected from a crystallization method using a laser at low temperature, a crystallization method using a metal, a crystallization method using a metal and capping layer (SGS crystallization method), and equivalents thereof; however, the crystallization method is not limited thereto. The crystallization method using the laser may be ELA (Excimer Laser Annealing), SLS (Sequential Lateral Solidification), TDX (Thin Beam Direction Crystallization), and the like; however, the crystallization method is not limited thereto. The crystallization method using the metal may be SPC (Solid Phases Crystallization), MIC (Metal Induced Crystallization), MILC (Metal Induced Lateral Crystallization), and the like; however, the crystallization method is not limited thereto. The crystallization method using the metal and capping layer is SGS (Super Grained Silicon), and the like; however, the crystallization method is not limited thereto. The thin film transistor may be at least any one selected from PMOS, NMOS, and equivalents; however, the conductive form of the thin film transistor is not limited thereto.
The catalytic metal may remain in the active layer 240. In particular, the catalytic metal may remain in the active layer 240 when the active layer 240 is the amorphous silicon, microsilicon, polysilicon, and organic material.
The catalytic metal may be selected from the group comprising Ni, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Mo, Tr, Ru, Rh, Cd, Pt, and equivalents and combinations thereof; however, the material of the catalytic metal is not limited thereto. As described below, the catalytic metal is formed during the crystallization process converting the amorphous silicon to the polysilicon.
The catalytic metals which remain in the alignment mark 230, 230a and the active layer 240 may have the volume density similar to each other. Particularly, when the alignment mark 230, 230a is formed on the buffer layer, the density of the catalytic metal which remains in the alignment mark 230, 230a and the active layer 240 are almost identical. Indeed, when the alignment mark 230, 230a is formed on the buffer layer, the volume density of the catalytic metal which remains in the alignment mark 230, 230a and the active layer 240 is approximately 1.0×1016 to 1.0×1020 atoms/cm3. When the volume density of the catalytic metal is greater than 1.0×1020 atoms/cm3, a leakage current may be generated, and thus it is not preferable.
Here, the SGS crystallization method is a crystallization method which converts the amorphous silicon to the polysilicon with relatively large grain size through heat-treatment after the capping layer and the catalytic metal are formed on the amorphous silicon. If the active layer 240 is formed by the SGS crystallization method, then no grain boundary or at least one grain boundary is formed therein. When the alignment mark 230, 230a is formed as a polysilicon, no grain boundary or at least one grain boundary is also formed on the alignment mark 230, 230a.
The gate insulating layer 250 may be formed on the upper surface of the alignment mark 230, 230a and the active layer 240. The gate insulating layer 250 may be formed on the buffer layer 220, which may circumscribe the alignment mark 230, 230a and the active layer 240. The gate insulating layer 250 may be formed of at least any one selected from the group consisting of a silicon oxide film, a silicon nitride film, an inorganic film, and equivalents thereof; however, the gate insulating layer 250 is not limited thereto.
The gate electrode 260 may be formed on the upper surface of the gate insulating layer 250. More specifically, the gate electrode 260 may be formed on the gate insulating layer 250 in area corresponding to the channel region 241 of the active layer 240. The gate electrode 260 forms the channel of the hole or electron in the channel region 241 by applying an electric field to the lower channel region 241 of the gate insulating layer 250. The gate electrode 260 may be made of a material selected from a typical metal (Mo, MoW, Ti, Cu, Al, AlNd, Cr, Mo alloy, Cu alloy, Al alloy, etc.), a doped polysilicon, and equivalents thereof; however, the gate electrode 260 is not limited thereto.
The interlayer dielectric layer 270 may be formed on the upper surface of the gate electrode 260. The interlayer dielectric layer 270 may be formed on the gate insulating layer 250 which may circumscribe the gate electrode 260. Further, the interlayer dielectric layer 270 may be formed on the gate insulating layer 250 corresponding to the alignment mark 230, 230a. The interlayer dielectric layer 270 may be formed of any one selected from the group consisting of polymer series, plastic series, glass series, and equivalents thereof; however, the material of the interlayer dielectric layer 270 is not limited thereto.
The source/drain electrode 280 may be formed on the upper surface of the interlayer dielectric layer 270. An electrically conductive contact 281 passing through the interlayer dielectric layer 270 may be formed to connect the source/drain electrode 280 and the active layer 240. That is, the source/drain region 242 and the source/drain electrode 280 of the active layer 240 are electrically coupled to each other by the electrically conductive contact 281. Further, the source/drain electrode 280 may be formed of the identical metal material as the gate electrode 260; however, the source/drain electrode 280 is not limited thereto. The above active layer 240 (i.e., thin film transistor) is defined as a coplanar structure. However, the active layer 240 is not restricted to the coplanar structure, but the active layer 240 may have any kind of structure of a thin film transistor, for example at least one of selected from the group consisting of an inverted coplanar structure, a staggered structure, an inverted staggered structure, and the equivalent thereof; however, the structure of the active layer 240 is not restricted thereto.
The insulating layer 290 may be formed on the upper surface of the source/drain electrode 280. The insulating layer 290 covers the interlayer dielectric layer 270 which may circumscribe or cover the source/drain electrode 280. Further, the insulating layer 290 is also formed on the interlayer dielectric layer 270 corresponding to the alignment mark 230, 230a. The insulating layer 290 may include a protective layer 291 and a planarization layer 292 formed on the upper surface of the protective layer 291. The protective layer 291 covers the source/drain electrode 280 and interlayer dielectric layer 270, and protects the source/drain electrode 280 and the gate electrode 260. The protective layer 291 may be formed of any one selected from the typical inorganic film, and equivalents thereof; however, the protective layer 291 of the protective layer 291 is not limited thereto. The planarization layer 292 covers the protective layer 291. The planarization layer 292, which is making the entire surface of the element flat, may be formed with any one selected from BCB (benzocyclobutene), acryl, and equivalents thereof; however, the planarization layer 292 is not limited thereto.
The organic light emitting diode 300 may be formed on the upper surface of the insulating layer 290. The organic light emitting diode 300 may include an anode 310, an organic thin film 320 formed on the upper surface of the anode 310, and a cathode 330 formed on the upper surface of the organic thin film 320. The anode 310 may be formed of at least any one of the group consisting of ITO (Indium Tin Oxide), ITO (Indium Tin Oxide)/Ag, ITO (Indium Tin Oxide)/Ag/ITO (IZO: Indium Zinc Oxide), and equivalents; however, the material of the anode 310 is not limited thereto. The ITO is a transparent conductive film with a small hole injection barrier in relation to the organic thin film 320 due to a uniform work feature, and the Ag reflects the light from the organic thin film 320 to the upper surface in a top emission type display. The organic thin film 320 (also described as an organic light emitting thin film) may include an emission layer (EML) to emit light by forming excitons as the electron and hole contact to each other, an electron transport layer (ETL) to control the moving velocity of the electron appropriately, and a hole transport layer (HTL) to appropriately control the moving velocity of the hole. An electron injecting layer (EIL) may be formed on the electron transport layer, and a hole injecting layer (HIL) may further be formed on the hole transport layer. Further, the cathode 330 may be formed of at least any one selected from Al, MgAg alloy, MgCa alloy, and equivalents thereof; however, the material of the cathode 330 is not limited thereto. However, in the front emission type display, the Al should be very thin; however, the electron injection barrier is increased as the thickness of the Al is decreased due to increased resistance. The MgAg alloy has a lower electron injection barrier than that of the Al, and the MgCa alloy has a lower electron injection barrier than that of the MgAg alloy. However, as the MgAg alloy and the MgCa alloy are sensitive to external environmental factors and can be oxidized to form an insulating layer, a protective layer may be formed on the MgAg and MgCa alloys to shield the MgAg and the MgCa alloys from the environment. The anode 310 of the organic light emitting diode 300 may be electrically coupled with the source/drain electrode 280 by an electrically conductive contact 311, which is formed by perforating the insulating layer 290 (the protective layer 291, the planarization layer 292). Aspects of the present invention may be applied to a bottom-emitting type which emits toward the bottom of the substrate 210, and a dual surface-emitting type which emits light toward both surfaces of the substrate 210.
The pixel defining film 293 may be further formed on the insulating layer 290 which is an outer circumference of the organic light emitting diode 300. The pixel defining film 293 defines the boundaries between a red organic light emitting diode, a green organic light emitting diode, and a blue organic light emitting diode, and thus making the emitting boundary region between the pixels more clear. The pixel defining film 293 may be formed with at least any one selected from polyimide, and equivalents thereof; however, the material of the pixel defining film 293 is not limited thereto. The pixel defining film 293 may be formed on the insulating layer 290 corresponding to the alignment mark 230, 230a; however, the pixel defining film 293 can be omitted in some cases.
Referring
Referring to
As shown in
As shown in
As shown in
As shown in
Here, the diffusion preventing layer 351 may be made of any one selected from a silicon oxide film, and equivalents thereof; however, the diffusion preventing layer 351 is not limited thereto. The diffusion layer 352 may be made of any one selected from a silicon nitride film, and equivalents thereof; however, the diffusion layer 352 is not limited thereto.
At least one the opening 353, which is formed in the diffusion preventing layer 351, is formed in a region corresponding to the display region 211 of the substrate 210. At this time, with reference to the align mark 240, the opening 353 may be accurately formed in the desired location. Therefore, the grain boundary of the polysilicon has a large size and a uniform directional property in the opening 353 formed on the display region 211. The size and position of the opening 353 formed on the display region 211 are designed according to the size and the position of the active layer 240, i.e., the thin film transistor.
As shown in
Here, if the capping layer 350, i.e., in the state that the catalytic metal 354 is put on the diffusion layer 352, is heat-treated to a specific temperature, the polysilicon having a macro-grain boundary is formed as the catalytic metal 354 passes through the opening 353 of the capping layer 350 and a crystallization seed is formed.
The catalytic metal 354 applied to the capping layer 350 may be formed to have the volume density of approximate 1.0×1018 to 1.0×1022 atoms/cm3. When the volume density of the catalytic metal 354 is approximately 1.0×1018 atoms/cm3 and below, then the crystallization according to the SGS crystallization method is not sufficiently achieved, and when the volume density of the catalytic metal 354 is approximately 1.0×1022 atoms/cm3 and above, then the leakage current is increased because of excessive catalytic metal 354 remains in the alignment mark 230, the active layer 240, and the buffer layer 220.
The catalytic metal 354 may be selected from the group comprising Ni, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Mo, Tr, Ru, Rh, Cd, Pt, and equivalents and combinations thereof; however, the material of the catalytic metal 354 is not limited thereto.
It is preferable that the heat treatment temperature is controlled to be 400 to 700° C. When the heat treatment temperature is 400° C. and below, then the crystallization by the catalytic metal 354 is not sufficiently achieved, and when the heat treatment temperature is 700° C. and above, then the substrate 210 may melt.
According to the processes, the catalytic metal 354 remains in the buffer layer 220, the alignment mark 230, and the active layer 240. The catalytic metal 354 is diffused throughout the active layer 240 as well as the buffer layer 220 and the alignment mark 230 by the heat treatment process. The catalytic metal 354 is controlled to have the volume density of approximately 2.0×1018 atoms/cm3 and below in order to minimize the leakage current.
When the alignment mark 230 is formed underneath the buffer layer 220, the volume density of the catalytic metal 354 has the value less than 2.0×1018 atoms/cm3. However, when the alignment mark 230 is formed on the buffer layer 220, the volume density of the catalytic metal 354 is almost identical as that of the catalytic metal 354 remaining in the active layer 240. For example, in the alignment mark 230 and the active layer 240 formed on the buffer layer 220, the volume density of the catalytic metal 354, which remains in the alignment mark 230 and the active layer 240, is controlled to be 1.0×1016 to 1.0×1020 atoms/cm3.
It is possible to form the polysilicon having the desired grain boundary and the desired direction in the desired position as the position control opening 353 is formed in the desired position of the capping layer 350 by using the alignment mark 230. The thin film transistor with optimal specifications is manufactured as the thin film transistor is formed by the polysilicon. Further, such a crystallization method is referred to as a SGS crystallization method, as described above.
As shown in
A patterning operation may be effected after the capping layer removing operation (S7). That is, the amorphous silicon or the polysilicon (except the region to be used as an active layer 240) is removed from the non-display region 212 and display region 211 by etching. The position of the patterning of the active layer 240 is selected with reference to the alignment mark 230.
As shown in
The source/drain regions 242 is formed by ion injecting a p-type impurity and an n-type impurity into the active layer 240, which are positioned at both sides of the gate electrode 260, and by activating them. And, the electrically conductive contact 281 is formed after the interlayer dielectric layer 270 is formed, and finally the source/drain electrode 280 is formed to be electrically coupled to the source/drain region 242 of the active layer 240, and the source/drain electrode 280 is patterned. In this process, the source/drain electrode 280 is formed by patterning the source/drain electrode 280 at a predetermined distance from the alignment mark 230.
Further, the insulating layer 290 is formed on the source/drain electrode 280 and the interlayer dielectric layer 270. As described above, the insulating layer 290 may comprise a protective layer 291 and a planarization layer 291. The protective layer 291 covers the source/drain electrode 280 and the interlayer dielectric layer 270. The protective layer 291 may be formed by depositing or coating a material selected from the typical inorganic film, and equivalents thereof. The planarization layer 292, which is to make the entire surface of the partially-constructed OLED flat, may be formed by depositing or coating a material selected from BCB (benzocyclobutene), acryl, and equivalents thereof.
The insulating layer 290 formed on the interlayer dielectric layer 270 and including the protective layer 291 and the planarization layer 292 may also be formed on the non-display region 212 corresponding to the alignment mark 230. The pixel defining film 293 may further be formed, and the pixel defining film 293 may also be formed on the non-display region 212 corresponding to the alignment mark 230. The pixel defining film 293 is formed by depositing or coating at least any one selected from polyimide, and equivalents thereof. The organic light emitting diode 300 is exposed by a photoresist, a coating, an exposure, a development, an etching, a photoresist peeling process, and the like.
Finally, in the organic light emitting diode forming operation (S9), the anode 310, the organic thin film 320, and the cathode 330 are formed on the insulating layer 290 in sequence as shown in
The organic thin film 320 may formed of a hole injecting layer (HIL) to improve the injection efficiency of the hole; a hole transport layer (HTL) to control the moving velocity of the hole appropriately; an emission layer (EML) to emit light by forming excitons as the electron and hole combine with each other; an electron transport layer (ETL) to control the moving velocity of the electron appropriately; and an electron injecting layer (EIL) to improve the injection efficiency of the electron in sequence; however, the organic thin film 320 is not limited thereto. For example, the organic thin film 320 may be formed by a wet coating method, such as a spin coating that applies the coating in the liquid state, a deep coating, a spray method, a screen printing method, an ink-jet printing method, and so on, or by a dry coating method, such as a sputtering, a vacuum evaporation, and so on.
The cathode 330 is formed on the upper surface of the electron injecting layer (EIL) in the organic thin film 320. The cathode 330 may be formed by depositing at least any one selected from Al, MgAg alloy, MgCa alloy, and equivalents thereof; however, the material or the manufacturing method of the cathode 330 is not limited thereto. For example, the cathode 330 may be formed by at least any one method selected from RF sputtering, DC sputtering, ion-beam sputtering, and vacuum evaporation method. After that, a desired size of the cathode 330 is formed in the desired position by a photoresist, a coating, an exposure, a development, an etching, a photoresist peeling method, and the like. Furthermore, when the front-emitting type display uses Al as the cathode 330, then the thickness should be very thin to increase a light emission rate. Thus, the electron injection barrier may be increased as the resistance is increased. Therefore, at least any one of the MgAg alloy, the MgCa alloy, or the equivalent thereof may be used as the cathode 330. The cathode 330 may be formed by one of ITO and IZO. Here, the MgAg alloy and the MgCa alloy are sensitive to external environment and form an insulating layer by oxidation, and seal the display.
Furthermore, in the phosphorescent organic light emitting diode, a hole blocking layer (HBL) may be selectively formed between the emission layer (EML) and the electron transport layer (ETL), and an electron blocking layer (EBL) may be selectively formed between the emission layer (EML) and the hole transport layer (HTL).
The organic thin film 320 may be formed as a thin organic light emitting diode, which reduces it's thickness by bonding two kinds of layers. For example, it is possible that a hole injection transport layer structure, which combines the hole injection layer (HIL) and the hole transport layer (HTL), or an electron injection transport layer structure which combines the electron injection layer (EIL) and the electron transport layer (ETL), may be formed selectively. The object of the slim organic light emitting diode is to increase the luminous efficiency.
An optional buffer layer may be formed between the anode and the emission layer. The optional buffer layer is classified into an electron buffer layer to buffer the electrons and a hole buffer layer to buffer the holes. The electron buffer layer may be formed between the cathode and the electron injection layer (EIL), and the electron buffer layer may be formed to replace the electron injection layer (EIL). The stack structure of the organic thin film 320 may be emission layer/electron transport layer/electron buffer layer/cathode. Also, the hole buffer layer may be selectively formed between the anode and the hole injection layer (HIL), and it may replace the feature of the hole injection layer (HIL). Here, the stack structure of the organic thin layer 320 may be anode/hole buffer layer/hole transport layer/emission layer.
The possible stack structures in relation to the above-mentioned structures are as follows:
a) Normal Stack Structure
b) Normal Slim Structure
c) Inverted Stack Structure
d) Inverted Slim Structure
Furthermore, aspects of the present invention may be applied to a bottom-emitting type display, which emits light toward the bottom or lower side of the substrate 210, and a dual surface-emitting type, which emits light toward and away from the upper surface of the substrate 210.
When the alignment mark is formed on the buffer layer, the density of the catalytic metal which remains in the alignment mark and the active layer is almost identical. Indeed, when the alignment mark is formed on the buffer layer, the volume density of the catalytic metal which remains in the alignment mark and the active layer is approximately 1.0×1016 to 1.0×020 atoms/cm3. When the volume density of the catalytic metal is 1.0×1020 atoms/cm3 and above, the leakage current may be generated, and thus it is not preferable.
Furthermore, the density of the catalytic metal of the active layer decreases slightly closer to the substrate as shown in
The characteristic of the thin film transistor in which the position control is not achieved, and the characteristic of the thin film transistor in which the position control is achieved according to aspects of the present invention are described in the Table 1.
As described in the Table 1, the average threshold voltage (Vth) was 2.9V with a standard deviation of the threshold voltage (Vth) of 0.1V in the thin film transistor according to the conventional invention; however, the average threshold voltage (Vth) was 3V with a standard deviation of the threshold voltage (Vth) of 0.05V in the thin film transistor according to aspects of the present invention, and thus it is improved.
The average S-factor was 0.48V/dev with a standard deviation of the S-factor of 0.03V/dev in the thin film transistor according to the conventional invention; however, the average S-factor was 0.44V/dev with a standard deviation of the S-factor of 0.01V/dev in the thin film transistor according to aspects of the present invention, and thus it is improved.
Finally, the average off current was 6.30×1012 A/μm with a standard deviation of the off current of 1.10×10−11 A/μm in the thin film transistor according to the conventional invention; however, the average of the off current was 1.20×10−12 A/μm with a standard deviation of the off current of 4.10×10−13 A/μm in the thin film transistor according to aspects of the present invention, and thus it is improved.
The organic light emitting display and the fabricating method thereof may form the polysilicon or the active layer (thin film transistor) with an optimal position by forming the alignment mark on the non-display region of the substrate. That is, the characteristic dispersion between the diodes may be considerably improved by forming the polysilicon having a grain boundary of optimal size, direction, and position by using the alignment mark and by forming the active layer (thin film transistor) at an optimal position at a predetermined distance from the alignment mark.
For example, the thin film transistor formed by the above-mentioned method had an average S-factor of 0.44V/dev with a standard deviation of 0.01V/dev. Also, the thin film transistor had an average off current of 1.20×10−12 A/μm with a standard deviation of 4.10×10−13 A/μm.
Furthermore, the organic light emitting diodes, which are electrically coupled to the thin film transistor formed by the above mentioned method, have a uniform luminance, even as the size of the panel is increased.
Although a few embodiments and aspects of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-138321 | Dec 2006 | KR | national |
