JP2003140570A - Electroluminescence display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the deficiency of linearity and the nonuniformity of a picture caused by the early effect and the kink current of a thin film transistor in an electroluminescence display device. SOLUTION: In this display device, the early effect and the kink current of the thin film transistor are prevented by grounding the channel part of the thin film transistor while bring an opposite conductive region into contact with the channel part and, thus, the linearity and the uniformity of the picture are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type electroluminescence display device driven by an electroluminescence element and a thin film transistor.

[0002]

2. Description of the Related Art Recently, electroluminescence (Electro Luminescence:
Abbreviated as "electroluminescence". ) Electroluminescent display devices using CRT or LC
Has attracted attention as a display device to replace the D.
Practical application and research and development of thin-film organic materials used as electroluminescent element materials are becoming active.

For example, an organic electroluminescence display device driven by a simple matrix has already been put into practical use.
On the other hand, research and development of an active matrix type electroluminescence display device using a thin film transistor (hereinafter abbreviated as “TFT”) for driving electroluminescence is under way.

FIG. 8 shows an equivalent circuit diagram of the organic electroluminescence display device, and FIG. 9 shows a plan view of a unit pixel of the organic electroluminescence display device.
0 shows a sectional view taken along the line CC ′ of FIG. 9.

As shown in FIG. 8, a gate bus line 10 is provided.
A unit pixel 108 for displaying is formed in a region surrounded by 1 and the source bus line 102. A first TFT 104, which is a switching element, is provided near the intersection of both signal lines.
Is provided, the drain of the TFT 104 is connected to the storage capacitor 107, and a second TFT for supplying current to the organic electroluminescence element to drive it.
It is connected to the gate electrode 105. Second TFT1
The drain electrode 05 is connected to the anode side of the organic electroluminescence element, and the source is connected to the current supply bus line 103 for driving the organic electroluminescence element.

The storage capacitor 107 holds the voltage applied to the gate of the second TFT 105 until the image signal is programmed in the next frame. These constitute a TFT array arranged in a matrix on the substrate, and an image signal is programmed in each pixel via the first TFT 104 for signal acquisition, and the programmed image signal is held in a storage capacitor. , An image is displayed by controlling the gate voltage of the driving TFT and passing a current through the electroluminescent element via the driving TFT.

Next, regarding the manufacturing process of the TFT array,
This will be described with reference to FIGS. 9 and 10. First, on the transparent insulating substrate 1 made of quartz glass, non-alkali glass, or the like,
Via the buffer layer 2 for preventing the diffusion of impurities from the substrate, polycrystalline silicon (hereinafter, referred to as "p-S" which also serves as one of the semiconductor layers of the first and second TFTs and one of the storage capacitors).
abbreviated as "i". ) 3 is formed. And the first TF
After phosphorus (P) is injected as an impurity into the source region 3-2 and the drain region 3-3 of T and the electrode portion of the storage capacitor, SiO 2 to be the gate insulating film 4 is deposited on the entire surface by the plasma CVD method. Then, the gate electrode 5 and the gate bus line 101 are formed, and the gate electrode 5 is used as a mask.
LDD (Lightly Doped Drain) of the first TFT 104
Phosphorus is implanted in the region 3-4 and boron (B) is implanted in the source / drain regions of the second TF 105. At this time, at least when boron is injected, a resist or the like is arranged on the first TFT 104 to prevent double injection.

After that, the interlayer insulating film 6 is deposited, and the source electrode 8, the drain electrode 9, the source bus line 102, and the current supply bus line 103 are provided through the contact hole 7.
Is formed of aluminum or the like to complete the TFT array.

Next, a process of forming an electroluminescence element will be described. In order to flatten the surface of the completed TFT array, a flattening film 10 is formed, and a pixel electrode 12 which also serves as an anode of organic electroluminescence is formed of ITO through a contact hole 11. After that, a hole transportation layer (Hole Transportation Layer: below, on the pixel electrode by a vapor deposition method using a metal mask,
Abbreviated as "HTL". ), Emission Layer:
Hereinafter, it is abbreviated as "EML". ) And electron transport layer (Electron
Transportation Layer: Hereinafter, abbreviated as "ETL". ) A layer also serving as 14 is continuously vapor-deposited, and finally an electron injection layer (hereinafter, abbreviated as “EIL”) and an electrode 15 also serving as a cathode are laminated.

As the HTL, for example, α-NPD is used. Examples of the EML include a quinolinol aluminum complex (hereinafter abbreviated as “Alq3”) doped with DCJT as a red (R) color material, and Alq3 doped with quinacridone as a green (G) color material, BPVBi is used as the blue (B) color material. EIL is also used as EML, so it is omitted. A material in which lithium (Li) is mixed with aluminum (Al) is used for the electrode that also serves as the EIL and the cathode.

At this time, when R, G, and B are separately applied to each pixel by vapor deposition, appropriate materials are vapor-deposited on the TFT array substrate through a metal mask 16 made of a metal material as shown in FIG. At this time, it is desirable that the substrate and the mask be in contact with each other or as close to each other as possible. This is because when the distance is large, the vapor deposition film spreads to the adjacent pixel and the film thickness accuracy cannot be secured.

The light emitting principle and operation of the organic electroluminescence device are as follows: holes injected from the pixel electrode 12 as an anode and electrons injected from the cathode 15 are recombined inside the EML to form an organic molecule forming a light emitting layer. Are excited to generate excitons. This exciton radiates or heat deactivates and returns to the ground state, but the radiation deenergization, that is, light emission, causes the emitted light to be emitted from the transparent anode through the transparent insulating substrate to the outside, It emits light.

[0013]

However, the following problems occur in the above configuration.

FIG. 12 shows the drain current-drain voltage characteristics of the second TFT, and the problem will be described with reference to FIGS. 8 and 12. When the first TFT 104 is selected, the source bus line 102 supplies a voltage and current according to an image signal to be programmed, and charges the storage capacitor 107.

When the first TFT is deselected,
The signal programmed into the storage capacitor causes a second TF
T105 is turned on. Then, a constant current flows from the current supply bus line 103 to the organic electroluminescence element via the second TFT, and light is emitted. Figure 12-
In (a), the state of the second TFT will be described in more detail.
During the selection period of the first TFT, the second TFT exhibits a diode characteristic, so the potential changes along the diode characteristic indicated by the dotted line, and is saturated at point S, for example. However, when the first TFT is deselected and a current flows through the electroluminescent element, the storage capacitor holds the gate voltage of the second TFT constant,
The drain voltage changes because the current supply line changes from the source bus line to the current supply bus line. That is, the operating point moves to the right along the arrow on the output curve of the second TFT. Then, the point T, which intersects the load curve of the organic electroluminescence element, is in the display state.

However, in the case of a thin film transistor,
Due to the Early effect and kink current caused by the body being in a floating state, the current value also changes in the so-called saturation region, so that the current values at points S and T are different.

Therefore, a variation occurs between the input signal and the output, which causes a problem of lack of linearity.

In addition, the Early effect and the kink current are caused by the TFT.
If they vary from one to another, there arises a problem that the variations cause variations in output and lead to unevenness and non-uniformity in display. Further, even if the Early effect or the kink current is constant for each pixel, if the threshold voltage of the second TFT of each pixel varies, the output current varies as shown in FIG. 12B. Therefore, there is a problem that it causes display unevenness and non-uniformity.

In view of the above points, an object of the present invention is to provide an electroluminescent display device having high linearity and capable of uniform display, and a method for manufacturing the same.

[0020]

According to the present invention, in order to solve these problems, a semiconductor layer having a conductivity type opposite to that of a source / drain region is brought into contact with a channel portion of a second TFT,
With the structure of being grounded, it is possible to obtain an electroluminescent display device that suppresses the Early effect and kink current, has high linearity, and has excellent display uniformity.

In the electroluminescence display device according to claim 1 of the present invention, an electroluminescence element, a first thin-film transistor for taking in a signal for driving the electroluminescence element, and the electroluminescence element are provided on a substrate having at least a surface having an insulating property. An electroluminescence display device in which unit pixels, which are provided with at least two thin film transistors of a second thin film transistor driven by applying a current to an electroluminescence element, are arranged in a matrix, wherein the second thin film transistor has at least a channel. A semiconductor layer including a region and one conductivity type source / drain region, an insulating layer, a gate electrode, a source / drain electrode, and a source / drain region opposite to the source / drain region in contact with the channel region;
It is characterized by comprising an electrode electrically contacting a part of the opposite conductivity type semiconductor layer. According to the present invention, it is possible to provide an electroluminescent display device having high linearity and excellent display uniformity.

According to a second aspect of the present invention, there is provided an electroluminescence display device in which unit pixels each including at least an electroluminescence element and a plurality of thin film transistors are arranged in a matrix on a substrate having at least an insulating surface. A luminescence display device, which is a first for capturing a signal from a source bus line by controlling a first gate bus line.
A first thin film transistor, a second driving thin film transistor for controlling a driving current flowing through an organic electroluminescence element, and a first switching thin film transistor for switching a signal current to the first thin film transistor, substantially in synchronization with the first thin film transistor. A third thin film transistor, a fourth thin film transistor that functions as a switch for switching the signal current to the electroluminescent element after writing the signal current by controlling the second gate bus line, and programming the signal current. At least includes a storage capacitor that holds the gate voltage of the thin film transistor even after the writing time, and the second thin film transistor has at least a channel region and a source of one conductivity type.
A semiconductor layer including a drain region, an insulating layer, a gate electrode, a source / drain electrode, a semiconductor layer opposite to the source / drain region in contact with the channel region, and a part of the opposite conductivity type semiconductor layer are electrically connected to each other. It is characterized by comprising an electrode in contact with. According to the present invention, it is possible to provide an electroluminescent display device having high linearity and excellent display uniformity.

According to a third aspect of the present invention, there is provided an electroluminescent display device in which unit pixels each including at least an electroluminescent element and a plurality of thin film transistors are arranged in a matrix on a substrate having at least a surface having an insulating property. A luminescence display device, which is a first for capturing a signal from a source bus line by controlling a first gate bus line.
The first thin film transistor, the second driving thin film transistor for controlling the driving current flowing through the organic electroluminescence element, the fifth conversion thin film transistor through which the signal current flows, and the second gate bus line for controlling the signal current. A sixth thin film transistor for switching that short-circuits the gate and drain of the fifth thin film transistor during the writing period, and programming the signal current to set the gate voltages of the second and fifth thin film transistors to the writing time. The second thin film transistor includes at least a storage capacitor to be held thereafter, and the second thin film transistor is in contact with a semiconductor layer including at least a channel region and a source / drain region of one conductivity type, an insulating layer, a gate electrode, a source / drain electrode, and the channel region. The opposite conductivity type to the source / drain region It is characterized by comprising a semiconductor layer and an electrode electrically contacting a part of the opposite conductivity type semiconductor layer. According to the present invention, the linearity is high,
It has an effect of providing an electroluminescence display device having excellent display uniformity.

According to a fourth aspect of the present invention, there is provided an electroluminescence display device in which unit pixels each including at least an electroluminescence element and a plurality of thin film transistors are arranged in a matrix on a substrate having at least an insulating surface. A luminescence display device, which is a first for capturing a signal from a source bus line by controlling a first gate bus line.
1 thin film transistor, a second driving thin film transistor for controlling a driving current flowing through the organic electroluminescence element, and a gate of the second thin film transistor during a writing period of the signal current by controlling a second gate bus line. A seventh thin film transistor for switching, which short-circuits between drains, an eighth thin film transistor for switching which causes a current to flow through the electroluminescent element by controlling a third gate bus line, and the signal voltage are programmed, and the second thin film transistor is programmed. At least a first storage capacitor that holds the gate voltage of the thin film transistor even after the writing time and a second storage capacitor that compensates for the threshold voltage of the second thin film transistor are included, and the second thin film transistor has at least a channel region. One conductivity type source / drain region A semiconductor layer including a region, an insulating layer, a gate electrode, a source / drain electrode, a semiconductor layer opposite to the source / drain region in contact with the channel region, and a part of the opposite conductivity type semiconductor layer electrically. It is characterized in that the electrodes are in contact with each other. According to the present invention, it is possible to provide an electroluminescent display device having high linearity and excellent display uniformity.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is an equivalent circuit diagram for explaining an electroluminescent display device according to a first embodiment of the present invention, FIG. 2 is a plan view of a main portion thereof, and FIG. 2 is a sectional view taken along the line AA 'in FIG. 2, and FIG.
It is a B'line sectional view.

Now, the organic electroluminescence display device will be specifically described with reference to FIGS. 1 to 3.

First, a SiO ₂ film of 100 to 6 is formed as a buffer layer 2 for preventing diffusion of impurities in the glass substrate 1.
Glass substrate 1 with a thickness of about 00 nm (#
1737 glass) and a film thickness of 30 to 1 by, for example, a plasma CVD method using silane (SiH4) as a source gas.
Amorphous silicon (hereinafter abbreviated as a-Si) at 50 nm
And hydrogen in a-Si at 400-450
After removing by heat treatment at ℃, for example, a-Si is locally heated and melted by XeCl excimer laser annealing and crystallized to obtain polycrystalline silicon (p-Si), and then a transistor is formed by photolithography and etching. The p-Si3 is left only where it is processed. Then, phosphorus (P) is injected into the source / drain region of the first TFT 104, which serves as a switching transistor, and the region that serves as one electrode of the storage capacitor 107, by an ion doping method that does not perform mass separation. The injection amount depends on the desired resistance value,
It is approximately 5 × 10 ¹⁴ to 1 × 10 ¹⁶ cm ⁻² . After that, TEOS (Tetraethylorthosilicate: (C ₂ H ₅ O) ₄ Si)
After depositing SiO ₂ to be the gate insulating film 4 with a thickness of 100 nm on the entire surface by the plasma CVD method using as a raw material gas,
For example, molybdenum tungsten (MoW) alloy is used to form the gate electrode 5 and the gate bus wiring 101 with a thickness of about 250 nm. Here, the MoW film thickness is 250 nm
However, the thickness is not limited to 250 nm, and may be appropriately selected according to design factors such as process and resistance value. Then, plasma of hydrogen-diluted phosphine (PH ₃ ) is generated using this gate electrode as a mask, the acceleration voltage is 70 kV, and the dose amount is 5 × 10 ^{12 to} 5 × 10 without mass separation.
By ion doping under the condition of ¹³ cm ^-2 ,
Form an LDD region. Next, a doping mask is formed using a photoresist, and hydrogen-diluted diborane (B
₂ H ₆ ) plasma is generated, the acceleration voltage is 50 kV without mass separation, and the dose is approximately 5 × 10 ¹⁴ to 1 × 10 ^16.
P-type source region 3-2 and drain region 3-3 are formed by ion doping under the condition of about cm ⁻² .

Thereafter, a photoresist is used to form the opposite conductivity type region 3-4, and the opposite conductivity type region 3-4 is formed.
By coating other than 4 and using this photoresist as a mask, plasma of hydrogen diluted phosphine (PH ₃ ) is generated,
Acceleration voltage is 70kV and dose is 5 × 1 without mass separation.
The opposite conductivity type region 3-4 is formed by ion doping under the condition of 0 ^{14 to} 5 × 10 ¹⁵ cm ^-2 .

Then, heat treatment is carried out at 450 to 600 ° C. for 1 hour in order to both crystallize the polycrystalline silicon and activate the implanted impurities. And TEOS (Tetraethylor
SiO ₂ is deposited on the entire surface as an interlayer insulating film 6 by a plasma CVD method using thosilicate: (C ₂ H ₅ O) ₄ Si) as a source gas, and then a contact hole 7 is formed. Then
For example, the lower layer is 100 nm Mo and the upper layer is 700 nm A.
l, and a metal wiring layer having a structure in which Mo is further laminated thereon. Here, Mo acts as a barrier layer. Then, by patterning the metal wiring layer by photolithography / etching, the source electrode 8, the drain electrode 9, the opposite conductivity type region electrode 18, the source bus line 102, and the current supply bus line 103 are formed to form the p-SiTFT. Is completed.

Thereafter, as a flattening film, for example, a photosensitive acrylic resin is applied to the entire surface in a film thickness of about 1 to 5 μm, exposed to light, and developed to form an opening in the drain electrode 9. Then, the pixel electrode 12 serving as an anode is made of ITO,
It is formed with a thickness of about 200 nm. Then, similarly, a photosensitive acrylic resin is applied to the entire surface. The film thickness is pixel electrode 1
Since it is better to cover the edge of ITO of No. 2, the film thickness must be larger than that of the pixel electrode. In addition, HTL, EML, E
When TL is vapor-deposited with a mask and also serves as a protective film, the thickness is preferably about 1 to 5 μm.

Then, exposure, development and post-baking are performed. Careful selection of bake temperature and time is required to control the taper angle during this post bake. It is also possible to control the taper shape by performing post-baking at a relatively low temperature, irradiating ultraviolet rays for bleaching, and finally performing final baking.

Next, an electroluminescence element is formed. First, using a metal mask, HTL / EML / ET
L14 is vapor-deposited in this order. HTL is, for example, α
-Use NPD. As the EML, for example, a quinolinol aluminum complex (hereinafter abbreviated as “Alq3”) doped with DCJT is used as a red (R) color material, and Alq is used.
Green (G) color material with quinacridone doped in 3,
BPVBi is used as the blue (B) color material. EIL is EML
Since it is also used as, it is omitted. Finally, EIL and cathode 1
An alloy of Al and Li having a function of 5 is 100 to 2
It was vapor-deposited to about 00 nm. In this state, the electroluminescence display device is completed for the time being, but since the organic electroluminescence element is very weak against humidity and oxygen, it is sealed using a metal cap or a glass cap, which is not shown in the figure. Control infiltration.

In the organic electroluminescence device thus completed, the thin film transistor in the pixel does not show the Early effect or the kink current, so that the display uniformity is improved. In the conventional method, about 20% of in-plane variation was generated almost randomly for each pixel, but in the present embodiment, it is improved to 10% or less.

The linearity is also improved.

In the first embodiment, a photosensitive acrylic resin is used as the insulating protective film 3, but a polyimide or novolac resin can be formed in almost the same manner.

Regarding EML, HTL and ETL, it is preferable that the EML is made of a phosphor having a fluorescent property in the visible region and having a good film-forming property.
And Be-benzoquinolinol (BeBq2),
2,5-bis (5,7-di-t-pentyl-2-benzoxazolyl) -1,3,4-thiadiazole, 4,
4'-bis (5,7-bentyl-2-benzoxazolyl) stilbene, 4,4'-bis [5,7-di- (2-
Methyl-2-butyl) -2-benzoxazolyl] stilbene, 2,5-bis (5,7-di-t-benzil-2
-Benzoxazolyl) thiophene, 2,5-bis ([5-α, α-dimethylbenzyl] -2-benzoxazolyl) thiophene, 2,5-bis [5,7-di-
(2-methyl-2-butyl) -2-benzoxazolyl] -3,4-diphenylthiophene, 2,5-bis (5-methyl-2-benzoxazolyl) thiophene,
4,4'-bis (2-benzoxazolyl) biphenyl, 5-methyl-2- [2- [4- (5-methyl-2-
Benzoxazolyl) phenyl] vinyl] benzoxazolyl, benzoxazoles such as 2- [2- (4-chlorophenyl) vinyl] naphtho [1,2-d] oxazole, 2,2 ′-(p-phenyl) Range vinylene)
-Benzothiazoles such as bisbenzothiazole, 2-
[2- [4- (2-benzimidazolyl) phenyl] vinyl] benzimidazole, 2- [2- (4-carboxyphenyl) vinyl] benzimidazole, and other fluorescent whitening agents such as benzimidazole, and tris (8- Quinolinol) aluminum, bis (8-quinolinol) magnesium, bis (benzo [f] -8-quinolinol) zinc, bis (2-methyl-8-quinolinolato) aluminum oxide, tris (8-quinolinol) indium, tris (5- Methyl-8-quinolinol) aluminum, lithium 8-quinolinol, tris (5-chloro-8-quinolinol) gallium, bis (5-chloro-8)
-Quinolinol) calcium, poly [zinc ("" -bis (8-hydroxy-5-quinolinonyl) methane), etc. 8
-A metal chelated oxinoid compound such as a hydroxyquinoline-based metal complex or dilithium epindridione,
1,4-bis (2-methylstyryl) benzene, 1,4
-(3-Methylstyryl) benzene, 1,4-bis (4
-Methylstyryl) benzene, distyrylbenzene,
1,4-bis (2-ethylstyryl) benzene, 1,4
-Styrylbenzene compounds such as bis (3-ethylstyryl) benzene and 1,4-bis (2-methylstyryl) 2-methylbenzene, 2,5-bis (4-methylstyryl) pyrazine, 2,5- Bis (4-ethylstyryl)
Pyrazine, 2,5-bis [2- (1-naphthyl) vinyl] pyrazine, 2,5-bis (4-methoxystyryl)
Distilpyrazine derivatives such as pyrazine, 2,5-bis [2- (4-biphenyl) vinyl] pyrazine, and 2,5-bis [2- (1-pyrenyl) vinyl] pyrazine, naphthalimide derivatives, and perylene derivatives Further, an oxadiazole derivative, an aldazine derivative, a cyclopentadiene derivative, a styrylamine derivative, a coumarin derivative, an aromatic dimethylidin derivative, etc. are used. Further, anthracene, salicylate, pyrene, coronene and the like can be used, and a phosphorescent material can also be used.

The HTL preferably has a high hole mobility, is transparent, and has a good film-forming property. In addition to α-NPD, triphenyldiamine (TPD), porphine, tetraphenylporphine copper, phthalocyanine, and copper phthalocyanine are preferable. Porphyrin compounds such as titanium phthalocyanine oxide, 1,1-bis {4- (di-P-tolylamino) phenyl} cyclohexane, 4,4 ′,
4 ″ -trimethyltriphenylamine, N, N,
N ', N'-tetrakis (P-tolyl) -P-phenylenediamine, 1- (N, N-di-P-tolylamino) naphthalene, 4,4'-bis (dimethylamino) -2-
2'-dimethyltriphenylmethane, N, N, N ',
N'-tetraphenyl-4,4'-diaminobiphenyl, N, N'-diphenyl-N, N'-di-m-tolyl-4, N, N-diphenyl-N, N'-bis (3-methyl Phenyl) -1,1'-4,4'-diamine, 4'-
Aromatic tertiary amines such as diaminobiphenyl and N-phenylcarbazole, 4-di-P-tolylaminostilbene, 4- (di-P-tolylamino) -4 '-[4-
Stilbene compounds such as (di-P-tolylamino) styryl] stilbene, triazole derivatives, oxazizazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, and annealed amine derivatives , Amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives,
Polysilane-based aniline-based copolymers, polymer oligomers, styrylamine compounds, aromatic dimethylidin-based compounds, and organic materials such as poly-3-methylthiophene are used. In addition, H of a polymer dispersion system in which a low molecular weight HTL organic material is dispersed in a polymer such as polycarbonate
TL is also used.

As ETL, Alq3, 1,3
-Bis (4-tert-butylphenyl-1,3,4-
Joxadiazole derivatives such as oxadiazolyl) phenylene (OXD-7), anthraquinodimethane derivatives,
Diphenylquinone derivatives and the like are also used.

Although a low molecular weight material is used in the present embodiment, a high molecular weight organic electroluminescent material can also be used.

Although an alloy of Al and Li is used as the cathode, the present invention is not limited to this, and Al, In, M
g, metal such as Ti, magnesium / silver (Mg: Ag) alloy, Mg alloy such as Mg—In alloy, Al / LiF alloy, Al—Sr alloy, Al alloy such as Al—Ba alloy, etc. May be. On the other hand, the pixel electrode serving as the anode is I
Although TO was used, ATO (Sb-doped Sn
O ₂ ), AZO (ZnO doped with Al) and the like are also used.

Light is taken out from the TFT array substrate side through the ITO of the pixel electrode, but not the Al: Li alloy of the cathode, for example, in order to increase the transmittance and ensure the electron injection efficiency, Thin magnesium / silver (Mg: A
g) By depositing an alloy of about 1 to 30 nm and then depositing ITO, which is a transparent conductor, by a sputtering method or the like, light can be extracted in the direction opposite to that of the array substrate, so that a reduction in the aperture ratio due to the TFT is prevented. It is possible to improve the light extraction efficiency. In this case, the sealing is not a metal cap, but sealing using a transparent substrate such as glass, or thin film sealing in which a transparent organic resin thin film and an inorganic material thin film are laminated on ITO is adopted.

Although the N-type TFT is used as the first TFT, it may be formed by a P-type TFT.

Further, p-S is also used as the semiconductor material of the TFT.
Not limited to i, a-Si, microcrystalline Si, single crystal Si, SiGe alloy, III-V group such as GaAs, II-VI group, or organic TFT can be used.

Further, the top gate type TFT has been described, but it goes without saying that the same effect can be obtained even if the bottom gate type TFT is adopted. Further, SiN _x or the like may be formed as a passivation film for the entire TFT after forming the source / drain electrodes.

(Embodiment 2) FIG. 5 shows an equivalent circuit diagram of the second embodiment. For the plan view and sectional view of the main parts,
Although the number of thin film transistors and the number of bus line wirings are increasing, there is no essential difference from the first embodiment, and the description thereof will be omitted. The creation method is also basically the same as that of the first embodiment, and therefore its description is omitted.

The operation principle will be described. From the source bus line to the first TFT by controlling the first gate bus line
A signal current is taken in by the signal current, and this signal current is programmed in the storage capacitor, and holds the gate potential of the second TFT for driving the electroluminescence element even after the signal writing period. The second TFT has an opposite conductivity type region similar to that shown in the first embodiment, and since this region is electrically grounded, it has a structure capable of suppressing the Early effect and kink current. ing. The second TFT allows a current for driving electroluminescence to flow from the power supply bus line based on the signal programmed in the storage capacitor. Third
Is connected to the same gate bus line as the first thin film transistor, and functions as a switch for flowing a signal current to the first thin film transistor. In this embodiment mode, the third thin film transistor is connected to the same gate bus line as the first thin film transistor, but an independent gate bus line may be provided and controlled by this. Fourth
The thin film transistor of (1) functions as a switch that switches the signal current to the electroluminescence element and flows the signal current after writing the signal current under the control of the second gate bus line. With this configuration, even if the threshold voltage of the second thin film transistor varies, the signal current can accurately flow through the electroluminescent element by switching between the third and fourth thin film transistors, so that the image uniformity can be further improved. Was improved and the variation was reduced to about 3% or less.

In this embodiment, the opposite conductivity type region is provided only for the second thin film transistor, but the opposite conductivity type region is similarly provided for some or all of the other first, third and fourth thin film transistors. It is possible to provide a region.

The type of the thin film transistor can be appropriately selected from P type and N type depending on the configuration of the whole pixel.

Needless to say, the present embodiment can take various variations similar to those of the first embodiment.

(Embodiment 3) FIG. 6 shows an equivalent circuit diagram of a third embodiment. For the plan view and sectional view of the main parts,
Although the number of thin film transistors and the number of bus line wirings are increasing, there is no essential difference from the first embodiment, and the description thereof will be omitted. The creation method is also basically the same as that of the first embodiment, and therefore its description is omitted.

The operation principle will be described. The first thin film transistor takes in a signal current from the source bus line by controlling the first gate bus line and programs the signal current into the storage capacitor. The storage capacitor holds the programmed charge, and holds the gate voltages of the second and fifth thin film transistors at a constant value after the writing time. Second
The thin film transistor of is for driving an organic electroluminescence element for controlling a driving current flowing through the organic electroluminescence element, has an opposite conductivity type region as shown in the first embodiment, and this region is an electrical region. Since it is grounded at, it is configured to suppress the early effect and kink current. The fifth thin film transistor is for conversion in which a signal current flows, and the sixth thin film transistor short-circuits the gate and drain of the fifth thin film transistor during the writing period of the signal current by controlling the second gate bus line. It works as a switch. In the circuit configuration of this pixel, a current mirror structure is formed by the fifth and second thin film transistors which form a pair and face each other. Therefore, if the characteristics of the second and fifth thin film transistors are the same, the same current, that is, the same current as the signal current flows through the electroluminescence element. Further, by appropriately adjusting the W / L of these transistors, the current multiplication factor can be arbitrarily selected, and the current can be amplified and passed. Therefore, the characteristics of the two adjacent thin film transistors (second and fifth) can be almost the same without making a great deal of effort. Therefore, the early effect and the effect of suppressing the kink current are combined, and further image uniformity is improved. Improved. The variation was about 4-5% or less.

In this embodiment, the opposite conductivity type region is provided only for the second thin film transistor, but the opposite conductivity type region is similarly provided for some or all of the other first, third and fourth thin film transistors. It is possible to provide a region.

The type of the thin film transistor can be appropriately selected from P type and N type depending on the configuration of the whole pixel.

It goes without saying that the present embodiment can take various variations similar to those of the first embodiment.

(Fourth Embodiment) FIG. 7 shows an equivalent circuit diagram of a fourth embodiment. For the plan view and sectional view of the main parts,
Although the number of thin film transistors and the number of bus line wirings are increasing, there is no essential difference from the first embodiment, and the description thereof will be omitted. The creation method is also basically the same as that of the first embodiment, and therefore its description is omitted.

The operation principle will be described. The first thin film transistor receives the signal voltage from the source bus line by controlling the first gate bus line,
Program to the storage capacity of. The second thin film transistor is a driving transistor that controls the driving current flowing in the organic electroluminescence element, and has an opposite conductivity type region as in the first embodiment, and this region is electrically Since it is grounded, it is configured to suppress early effects and kink current. The seventh thin film transistor short-circuits the gate and drain of the second thin film transistor during the write period of the signal current by controlling the second gate bus line, and the second storage capacitor is set to the threshold voltage of the second thin film transistor. It has a function of programming and compensating for variations in threshold voltage. The eighth thin film transistor acts as a switch for supplying a current to the electroluminescent element by controlling the third gate bus line. With this configuration, even if the threshold voltage of the second thin film transistor varies, it is compensated and the uniformity is improved. The image uniformity is further improved by combining the early effect and the effect of suppressing the kink current. The variation was about 5% or less.

In this embodiment, the opposite conductivity type region is provided only for the second thin film transistor, but the opposite conductivity type is similarly provided for some or all of the other first, third and fourth thin film transistors. It is possible to provide a region.

The type of the thin film transistor can be appropriately selected from P type and N type depending on the configuration of the whole pixel.

Needless to say, the present embodiment can take various variations as in the first embodiment.

[0061]

As described above, according to the electroluminescence display device of the present invention, it is possible to provide an electroluminescence display device having good image uniformity and high linearity and good image quality. The effect is great.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of an electroluminescence display device of the present invention.

FIG. 2 is a plan view of one pixel of an electroluminescence display device according to the present invention.

3 is a cross-sectional view taken along the line A-A 'in FIG.

FIG. 4 is a sectional view taken along line B-B ′ of FIG.

FIG. 5 is an equivalent circuit diagram of the electroluminescent display device according to the second embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram of the electroluminescence display device according to the second embodiment of the present invention.

FIG. 7 is an equivalent circuit diagram of the electroluminescence display device according to the second embodiment of the present invention.

FIG. 8 is an equivalent circuit diagram of a conventional electroluminescence display device.

FIG. 9 shows a conventional electroluminescence display device 1.
Pixel plan view

10 is a cross-sectional view taken along the line C-C ′ of FIG.

FIG. 11 is a cross-sectional view of an essential part showing a vapor deposition process of organic electroluminescence.

FIG. 12 is a diagram schematically showing the Early effect and kink current.

[Explanation of symbols]

1 glass substrate 2 buffer layer 3-1 p-Si (channel region) 3-2 p-Si (source region) 3-3 p-Si (drain region) 3-4 p-Si (LDD region) 3-5 p -Si (opposite conductivity type region) 4 gate insulating film 5 gate electrode 6 interlayer insulating film 7 contact hole 8 source electrode 9 drain electrode 10 planarizing film 11 opening 12 pixel electrode (ITO anode) 13 protective film 14 ETL (electron transport) Layer) / EML (light emitting layer) / HT
L (hole transport layer) 15 cathode (Al: Li) 16 metal mask 17 electroluminescent material deposition 18 electrode of opposite conductivity type region 101 gate bus line 102 source bus line 103 current supply bus line 104 first TFT 105 second TFT 106 Electroluminescence element 107 Storage capacitor 108 Unit pixel 109 Ground bus line 110 Opposite conductivity type region 111 First gate bus line 112 Second gate bus line 113 Third thin film transistor 114 Fourth thin film transistor 115 Fifth thin film transistor 116 Sixth thin film transistor 117 Seventh thin film transistor 118 Eighth thin film transistor 119 Second storage capacitor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/30 G09G 3/30 J H01L 29/786 H05B 33/14 A H05B 33/14 H01L 29/78 626B 614 F term (reference) 3K007 AB17 DB03 GA00 5C080 AA06 BB05 DD05 EE28 FF11 JJ03 JJ05 JJ06 5C094 AA03 AA55 BA03 BA27 CA19 EA04 EA07 5F110 AA15 HL02 BB02 GG04 GG04 GG02 GG04 GG02 GG04 GG02 GG04 GG02 GG04 GG02 GG04 GG04 GG02 GG04 GG02 GG04 GG02 NN03 NN04 NN23 NN24 NN27 NN35 NN72 PP03 PP35

Claims (4)

[Claims] 1. An electroluminescent element, a first thin-film transistor for capturing a signal for driving the electroluminescent element, and a first electrically driven thin film transistor for driving the electroluminescent element, at least on a substrate having an insulating property. An electroluminescent display device in which unit pixels each including at least two thin film transistors of the second thin film transistor are arranged in a matrix, wherein the second thin film transistor includes at least a channel region and a source of one conductivity type.
A semiconductor layer including a drain region, an insulating layer, a gate electrode, a source / drain electrode, a semiconductor layer opposite to the source / drain region in contact with the channel region, and a part of the opposite conductivity type semiconductor layer are electrically connected to each other. An electroluminescent display device comprising an electrode in contact with the electrode. 2. An electroluminescence display device in which unit pixels each including at least an electroluminescence element and a plurality of thin film transistors are arranged in a matrix on a substrate having at least a surface having an insulating property, and a first gate is provided. A first thin film transistor for taking in a signal that takes in a signal current from the source bus line by controlling the bus line, a second thin film transistor for driving that controls a driving current flowing through the organic electroluminescent element, and the first thin film transistor A third thin-film transistor for switching that causes a signal current to flow to the first thin-film transistor in synchronization with it, and a switch that switches the signal current to the electroluminescence device after writing the signal current by controlling the second gate bus line. age A fourth thin film transistor that operates, and at least a storage capacitor that programs the signal current and retains a gate voltage of the second thin film transistor after the writing time, the second thin film transistor having at least a channel region and one conductivity type. A semiconductor layer including a source / drain region, an insulating layer, a gate electrode, a source / drain electrode, and a semiconductor layer opposite to the source / drain region in contact with the channel region, and a part of the opposite conductivity type semiconductor layer. An electroluminescent display device, characterized in that it comprises an electrode in electrical contact with the. 3. An electroluminescence display device in which unit pixels each including at least an electroluminescence element and a plurality of thin film transistors are arranged in a matrix on a substrate having at least a surface having an insulating property, and a first gate is provided. A first thin film transistor for capturing a signal current that captures a signal current from a source bus line by controlling the bus line, a second thin film transistor for driving that controls a driving current flowing through an organic electroluminescent element, and a conversion thin film transistor for flowing a signal current. A fifth thin film transistor and a sixth switch for short-circuiting the gate and the drain of the fifth thin film transistor during the writing period of the signal current by controlling the second gate bus line.
A thin film transistor of, and programming the signal current,
A semiconductor layer that includes at least a storage capacitor that holds the gate voltages of the second and fifth thin film transistors even after the writing time, and the second thin film transistor includes at least a channel region and a source / drain region of one conductivity type; It comprises an insulating layer, a gate electrode, a source / drain electrode, a semiconductor layer opposite to the source / drain region in contact with the channel region, and an electrode electrically in contact with a part of the opposite conductivity type semiconductor layer. An electroluminescent display device characterized by. 4. An electroluminescent display device, in which unit pixels each including at least an electroluminescent element and a plurality of thin film transistors are arranged in a matrix on a substrate having at least a surface having an insulating property, and a first gate is provided. A first thin film transistor for taking in a signal voltage from the source bus line by controlling the bus line, a second thin film transistor for driving which controls a driving current flowing through the organic electroluminescence element, and a second gate bus line. A seventh switch for short-circuiting the gate and the drain of the second thin film transistor during the writing period of the signal current by control.
Of the thin film transistor, and an eighth thin film transistor for switching the current flowing through the electroluminescent element by controlling the third gate bus line, and the signal voltage are programmed, and the gate voltage of the second thin film transistor is programmed even after the writing time. At least a first storage capacitor that holds the second storage capacitor and a second storage capacitor that compensates the threshold voltage of the second thin film transistor are included, and the second thin film transistor includes at least a channel region and a source / drain region of one conductivity type. A semiconductor layer, an insulating layer, a gate electrode, a source / drain electrode, and a semiconductor layer opposite to the source / drain region in contact with the channel region;
An electroluminescent display device comprising an electrode electrically contacting a part of the opposite conductivity type semiconductor layer.