JP2000340359A - Driving device for organic EL element and organic EL display device - Google Patents

Abstract

(57) Abstract: An organic EL device driving device and an organic EL device that require a small number of power supplies and can be manufactured at low cost by forming devices having characteristics suitable for each driving condition in a small number of steps.
Implement a display device. SOLUTION: A first switching element for driving an organic EL element, a second switching element for driving the first switching element, and an organic layer driven by the switching element and involved in at least a light emitting function are provided. An organic EL element, the first switching element and the second switching element are formed on the same non-single-crystal silicon substrate, and the first switching element;
A driving device for an organic EL element having a different doping material from the second switching element was used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an organic EL device, and more particularly to a driving device for an organic EL device using a thin film transistor having a non-single-crystal semiconductor thin film as a base.

[0002]

2. Description of the Related Art Conventionally, in an organic EL display device (display), there has been known a technology for displaying an image by simply driving an XY matrix circuit (Japanese Patent Laid-Open No. 2-37).
385, JP-A-3-233891, etc.).
However, in such simple driving, line-sequential driving is performed, and when the number of scans is as large as several hundreds, the required instantaneous luminance is several hundred times the observed luminance. There was a problem.

(1) The driving voltage increases. Since the voltage is usually two to three times or more that under a DC steady voltage, the efficiency is reduced. Therefore, power consumption increases. (2) Since the amount of current flowing instantaneously becomes several hundred times, the organic light emitting layer is easily deteriorated. (3) As in the case of (2), since the flowing current is very large, a voltage drop in the electrode wiring becomes a problem.

The following active matrix drive has been proposed as a method for solving the above (1) to (3). That is, a display using ZnS, which is an inorganic substance, as a phosphor and further performing active matrix driving is disclosed (US Pat. No. 4,143,297).
issue). However, in this technique, since the inorganic phosphor is used, the driving voltage is as high as 100 V or more, which is a problem. A similar technique is IEEE TransElectro.
n Devices, 802 (1971). On the other hand, recently, a large number of displays that perform active matrix driving using an organic phosphor have been developed (Japanese Patent Laid-Open Nos. 7-122360 and 7-1223).
No. 61, JP-A-7-153576, JP-A-8-158
-54836, JP-A-7-111341,
JP-A-7-310290, JP-A-8-10937
0, JP-A-8-129359 and JP-A-8-129.
JP 241047 and JP-A-8-227276). In the above technique, the driving voltage is drastically reduced to 10 V or less by using an organic phosphor, and the efficiency is 3 lm / w to 15 liter when a highly efficient organic phosphor is used.
The efficiency is extremely high in the range of m / w, and the driving voltage of the high-definition display is 1/2 to 1 as compared with the simple driving.
/ 3, which is an excellent feature that power consumption can be reduced.

FIGS. 12 and 13 show a conventional example of a TFT drive circuit. Hereinafter, a conventional example of an active matrix will be described with reference to the drawings.

FIG. 12 is a panel block diagram. A display panel 1 has a display screen 1.
1, a shift register 12 for the X axis and a shift register 13 for the Y axis.

The display screen 11 is supplied with EL power, and the X-axis shift register 12 is supplied with shift register power and inputs an X-axis synchronization signal. Further, supply of power to the shift register and input of a Y-axis synchronization signal are performed to the Y-axis shift register 13. The output section of the X-axis shift register 12 has an output of an image data signal.

FIG. 13 is an enlarged explanatory view of part A of FIG. 12. One pixel (shown by a dotted square) of the display screen 11 has two transistors, one capacitor, and EL
The element is constituted by one element.

The light emitting operation of this one pixel is performed, for example, when the selection signal y1 is output from the Y-axis shift register 13 and the selection signal x1 is output from the X-axis shift register 12, when the transistor Ty11 and the transistor Ty11 are output. Tx1 turns on.

Therefore, the image data signal -VL is input to the gate of the drive transistor M11. As a result, a current corresponding to the gate voltage flows from the EL power supply to the drain and source of the drive transistor M11,
The EL element EL110 emits light.

At the next timing, the X-axis shift register 12 turns off the output of the selection signal x1 and turns off the selection signal x.
2 will be output, but the drive transistor M1
1 is held by the capacitor c11, so that the EL element EL110 is not selected until the next time this pixel is selected.
The above light emission will be sustained.

Therefore, even if the number of scanning lines increases and the time allocated to one pixel decreases, the driving of the organic EL element is not affected, and the contrast of the image displayed on the display panel decreases. Not even. Therefore, according to the active matrix system, display with much higher image quality can be performed as compared with the simple matrix system.

By the way, in the case of an organic EL element, since it is a current driving element, the emission luminance depends on the applied current density. For this reason, when the emission luminance is to be improved with the same pixel area, or when the number of pixels is increased in order to increase the definition of the entire screen, the driving time per pixel (time division time)
When the light emission luminance is to be further increased to compensate for this, it is necessary to increase the drive current. In this case, although it depends on the circuit configuration, an attempt to increase the drive current necessarily increases the drive voltage.

However, when an attempt is made to construct a switching element corresponding to a large current and a high voltage, an off-state leak current Ioff increases, which causes erroneous light emission and a decrease in contrast.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-voltage and large-current switching device and to use a switching element having a small off-state current to prevent erroneous light emission and contrast reduction. Another object of the present invention is to realize a driving device for an organic EL element capable of high-definition display and a display device using the same.

[0016]

That is, the above object is achieved by the following constitutions. (1) a switching element for driving an organic EL element;
An organic EL element driven by a switching element and having at least an organic layer involved in a light emitting function, wherein the switching element has an LDD structure. (2) The driving device of the organic EL element according to (1), wherein the switching element is a depression type. (3) An organic EL display device having a plurality of organic EL elements arranged in a matrix and a driving device of the organic EL element according to (1) or (2) for driving the organic EL elements.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An organic EL element driving device according to the present invention includes a switching element for driving an organic EL element and an organic EL element driven by the switching element and having at least an organic layer involved in a light emitting function. The switching element has an LDD structure.

As described above, the switching element for driving the organic EL element has the LDD structure, so that the channel region under the gate, the heavily doped region and the drain ( Or, a high-concentration low-concentration doped region is formed between the high-concentration doped region on the source side and the high-concentration low-concentration doped region. And the leakage current, that is, Ioff, can be suppressed.

The LDD (Lightly Doped Drain) structure is
For example, as shown in FIG. 1, a heavily doped region 2b serving as a source (or drain) side and a heavily doped region 2b serving as a drain (or source) side of an active layer formed on a silicon substrate 1, and a gate electrode 4, a structure in which a lightly doped region 2c is formed. In FIG. 1, an undoped active layer region 2a is formed directly below the gate electrode 4 using the gate electrode 4 as a mask. Further, a gate insulating film 3 is formed between the active layer and the gate electrode 4.

Lightly doped region 2c in LDD structure
The high-concentration doped region 2b on the source (or drain) side of the active layer formed on the silicon substrate 1, the high-concentration doped region 2b on the drain (or source) side, and the undoped region 2a Is preferably 0.5 to 3 μm, more preferably about 1 to 2 μm. If the length of the lightly doped region is too short, LD
It is difficult to obtain the effect of the D structure, and if the length is too long, the element characteristics deteriorate.

As a method of low concentration doping (light doping), a high concentration doping region on the source (or drain) side of the active layer and a high concentration doping region on the drain (or source) side of the active layer, and a gate electrode After doping the low-concentration doped region with a low concentration, and then doping the high-concentration region by masking only the low-concentration doped region, or forming a high-concentration region by masking the low-concentration region After that, a method of removing the mask and performing low concentration doping can be cited.

When doping at a low concentration, the doping method includes an ion plantation method and an ion implantation method, and the ion implantation method is preferable. As the ion implantation method, any of a distribution implantation method and a predeposition implantation method may be used.

The dose of the low-concentration region varies depending on the doping material, but is usually 1 × 10 ¹¹ to 1 × 10 ^14.
cm ⁻² , preferably about 1 × 10 ¹² to 1 × 10 ¹³ cm ⁻² . The acceleration voltage is preferably 30 to 100 keV
It is about.

The dose of the high-concentration region varies depending on the doping material, but is usually 1 × 10 ¹⁴ to 1 ×.
It is about 10 ¹⁶ . The accelerating voltage is preferably 50
It is about 80 keV.

As the doping material, a usual doping material used for manufacturing a semiconductor device can be used, and a suitable material may be selected and used depending on the characteristics of the device to be formed.

More specifically, when forming an n-type polycrystalline TFT, it is sufficient to dope P, As, Sb, etc. in the depletion type, and B, Al, etc. in the enhancement type. When a p-type polycrystalline TFT is formed, B, Al, etc. are used in the depletion type, and P, A are used in the enhancement type.
What is necessary is just to dope s, Sb, etc.

The drive device of the present invention mainly has the above-described switching element. In particular, when a display device is constructed, a drive switching element for driving the drive device, a shift register, etc. It consists of. In addition, any other elements required for driving an organic EL element serving as a pixel can be applied. The shift register in the present invention may have any configuration as long as it can generate a digit-increased output according to an input signal (data). Usually, the shift register is configured by a combination of flip-flops. Note that the shift register is used to sequentially select row elements or column elements of the display screen and to perform time-division driving, and a shift register having the same function as this is also included in the shift register of the present invention.

In the switching element of the present invention, a control electrode and a set of controlled electrodes are formed on a silicon substrate,
There is no particular limitation on the semiconductor element required to drive the L element, but a TFT (Thin Film Transistor) type is preferable in consideration of functioning as a display device.

FIG. 2 shows the switching element of the present invention.
This will be described more specifically with reference to FIG. Figure 2 shows the organic E
FIG. 3 is a plan view showing an example of a TFT array for driving an L element.

In FIG. 1, a source electrode 13 is connected to a source bus 11 and is connected to a source portion formed on a silicon substrate 21 via a contact hole 13a. On the silicon substrate 21, a gate bus 12 commonly connected to a TFT element of another pixel (not shown)
Are formed, and a gate electrode is formed at a portion where the gate bus 12 intersects the silicon substrate 21.

A drain wiring 14 is connected to a drain part formed on the silicon substrate with the source part and the gate electrode interposed therebetween through a contact hole 14a. The drain wiring 14 is connected to a gate line 15 via a contact hole 14b. The gate line 15 is formed on a silicon substrate 22 constituting the TFT 2 and is connected to one electrode of a capacitor 18. The other electrode of the capacitor 18 is connected to the ground bus 23.
And the source electrode 17 is connected to the source electrode 17 via a contact hole 17a.
Connected to the source part of FT1. Gate line 1
A gate electrode is formed at a portion where 5 intersects the silicon body 22.

A drain wiring 16 is connected through a contact hole 16a to a drain part formed on the silicon substrate with the source part and the gate electrode 15 interposed therebetween.
The drain wiring 16 forms one electrode of an organic EL element serving as a pixel or is connected thereto.

TFT 1 for directly driving this organic EL element
Corresponds to the switching element in the present invention.

The substrate used in the present invention is preferably insulating and made of a transparent material such as quartz, sapphire or glass. Here, “transparent” means that the organic EL display device has a property of transmitting sufficient light for practical use in an organic EL display device. For example, a material that transmits 50% or more, more preferably 70% or more of light in a desired emission wavelength band is considered to be transparent. In addition, low strain point glass is
A glass that warps at a temperature of about 700 ° C. or more.

In the present invention, the thin film transistor (T
FT) is used for driving an organic EL element.

The active layer of this switching element is, for example, a portion where an n + / i / n + region is formed,
Indicates an N-type doped portion, and i indicates an undoped portion. The doped portion of the active layer may be P + doped P-type. This active layer is preferably formed of polysilicon. Polysilicon shows a sufficient stability to energization compared to amorphous Si.

The α-Si layer as a polysilicon precursor can be laminated by various CVD methods, but is preferably laminated by a plasma CVD method. Then, KrF (248
nm) Anneal with an excimer laser such as a laser and crystallize. As a specific method, SID'9
6, Digestoftechnicalpapers
It is preferable to use a method as shown on pages 17 to 28.

As for annealing of the excimer laser, it is preferable to maintain the substrate temperature at 100 to 300 ° C., and it is preferable to anneal with a laser beam having an energy amount of 100 to 300 mJ / cm ² .

In addition, crystallization may be performed by using a generally used thermal annealing method. Further, by using both the thermal annealing method and the laser annealing method, more preferable results can be obtained.

The activated polysilicon has 900
There is a silicon thin film (a so-called high-temperature polysilicon film) formed through a heat treatment at about ° C and a silicon thin film (a so-called low-temperature polysilicon film) formed at a relatively low temperature of 600 ° C or lower. The active layer of the present invention may be either high-temperature polysilicon or low-temperature polysilicon.

The active layer, that is, the film thickness of α-Si is 100
Å800 °, preferably 300〜500 °.

The active layer (polysilicon layer) is patterned into islands by photolithography so as to have a configuration required as a switching element.

The substrate used is quartz having an insulating property,
Ceramic, sapphire, glass and the like can be used, but are preferably inexpensive materials such as low strain point glass. TFT-EL when a glass substrate is used
Avoids melting or distortion of the glass and out-diffusion of dopants in the active area.
On) is performed at a low process temperature to avoid on). In this way, all manufacturing steps on the glass substrate must be performed at 800 ° C. or less, preferably 600 ° C. or less.

In order to form a control electrode, an insulating gate material is preferably laminated on the polysilicon island and over the surface of the insulating substrate. The insulating material is preferably plasma CVD (PECVD) or low pressure CVD (L
Silicon dioxide (SiO ₂ ) deposited by chemical vapor deposition (CVD) such as PCVD. The thickness of the gate oxide insulating layer is preferably about 50-200 nm. The substrate temperature is preferably from 250 to 400 ° C., and in order to obtain a high-quality insulated gate material, annealing is preferably performed at from 300 to 400 ° C.
It is preferable to carry out at 600 ° C. for about 1 to 3 hours.

Further, as a control electrode, for example, a gate electrode is formed by vapor deposition or sputtering, and the gate electrode is patterned. The preferred thickness of the gate electrode is 100 to 500 nm.

As a preferable gate forming method, there is the following technique using polysilicon as a gate.

<N-type P-doped polysilicon> The gate electrode is formed by forming P-doped α-Si by a plasma CVD method.
This is polycrystallized by annealing at 600 ° C. to form n-type polycrystalline Si, which is patterned by photolithography.

If necessary, signal electrode lines and scanning electrode lines may be formed. A metal line such as an Al alloy, Al, Cr, W, and Mo is formed by photolithography.

When an Al gate is used, it is preferable to perform anodic oxidation twice for insulation.
Anodization is disclosed in detail in Japanese Patent Publication No. 8-15120.

Further, an n + or P + site is formed by ion doping. At this time, a high concentration doping region and a low concentration doping amount region are formed.

The contacts such as the drain and the source as controlled electrodes are made at the locations where the insulating film is opened. Among the above insulating films, SiO ₂ is obtained by using, for example, TEOS (tetraethoxysilane) as a gas at a substrate temperature of 250 to 400 ° C.
And can be obtained by PECVD. In addition, it can be obtained by setting the substrate temperature to 100 to 300 ° C. by ECR-CVD.

The interlayer insulating film can be formed, for example, by the following method. Etch-back method by plasma etching Various CVD methods, plasma CVD, PECVD (plasma enhanced CVD), LPCVD (low pressure CV
D) The SiO ₂ silica is preferably 0.2 μm by a method or the like.
m to 3 μm is formed.

By this method, a flattened interlayer insulating film (SiO ₂ ) can be obtained. In this method, PSG, BSG (phosphorus silica glass, boron silica glass), or a silicon nitride-based compound such as Si ₃ N ₄ can be used in addition to silica. As described above, the switching element is formed.

The electric field mobility of the switching element is preferably 60 (cm ² / V · sec) or less, particularly 30 to 50 (cm ^2).
/ V · sec).

Next, a more specific configuration of the switching element of the present invention and a manufacturing process thereof will be described with reference to the drawings.

First, as shown in FIG. 3, a sputtering method, various CVD methods, preferably plasma CVD
The α-Si layer 102 is stacked by a method or the like.

After that, as shown in FIG. 4, annealing and crystallization are performed by an excimer laser 115 or the like to form an active layer 102a.

Next, as shown in FIG.
3 over the polysilicon island 102a and the surface of the insulating substrate 101. The substrate temperature is 25
Annealing is preferably performed at 300 to 600 ° C. for about 1 to 3 hours in order to obtain a high quality insulated gate material.

Next, as shown in FIG.
4 is formed by vapor deposition or sputtering.

Next, as shown in FIG.
Then, a masking region of the photoresist 105 is patterned thereon to mask a low-concentration doping region. High-concentration ion doping 116 is performed on the patterned photoresist 105 and the gate electrode 104 to form n + or P + sites.

Next, as shown in FIG. 9, the patterned photoresist 105 is removed, and the gate electrode 10 is removed.
4, a low-concentration ion doping 116a is again performed to form a low-concentration doping region between the n + or P + portion and the gate electrode.

Further, signal electrode lines and scanning electrode lines are formed by photolithography.

Next, contacts such as a drain and a source are formed. The contact is made at a location where the insulating film 111 is opened. First, an SiO ₂ film is formed as an interlayer insulating layer by a normal pressure CVD method. Next, the interlayer insulating layer is etched to form a contact hole, and a drain / source connection portion is opened.

A drain wiring electrode 112 and a source wiring electrode 113 are formed on the opened drain and source connection portions, respectively, and connected to the drain and source electrodes. In this case, one of the drain and source electrodes is an organic EL.
Functions or is connected to a first electrode or a second electrode of the element. In the illustrated example, it is connected to ITO (115) which is a hole injection electrode. Further, an insulating film 114 is formed on the drain wiring electrode 112, and at the same time, an edge cover covering portions other than the pixel portion is formed to obtain a switching element as shown in FIG.

The connection with the electrodes of the organic EL element, such as the hole injection electrode, is made between the wiring electrode 113 and the hole injection electrode 115 as shown in FIG. , TiN or other connecting metal layer 116 may be formed.

Next, the structure of the organic EL device of the present invention will be described. An organic EL element has an organic layer containing at least an organic substance involved in a light emitting function between a first electrode and a second electrode. Then, light is emitted when electrons and holes provided from the first electrode and the second electrode recombine in the organic layer.

Either of the first electrode and the second electrode may be a hole injection electrode or an electron injection electrode, but usually, the first electrode on the substrate side is a hole injection electrode and the second electrode is a second electrode.
Are used as electron injection electrodes.

As the electron injection electrode, a substance having a low work function is preferable. For example, K, Li, Na, Mg, La, C
e, Ca, Sr, Ba, Al, Ag, In, Sn, Z
It is preferable to use a single metal element such as n or Zr, or a two-component or three-component alloy system containing them for improving the stability. As an alloy system, for example, Ag · Mg (A
g: 0.1 to 50 at%), Al.Li (Li: 0.01)
１４14 at%), In · Mg (Mg: 50 to 80 at%),
Al.Ca (Ca: 0.01 to 20 at%) and the like. Note that the electron injection electrode can also be formed by an evaporation method or a sputtering method.

The thickness of the electron injecting electrode thin film may be a certain thickness or more for sufficiently injecting electrons.
The thickness is preferably 1 nm or more, more preferably 3 nm or more. The upper limit is not particularly limited, but the thickness may be generally about 3 to 500 nm. An auxiliary electrode or a protection electrode may be further provided on the electron injection electrode.

The pressure during the deposition is preferably 1 × 10 ⁻⁸ to 1
The heating temperature of the evaporation source is 100 to 1400 ° C. for a metal material and 100 to 50 ° C. for an organic material at × 10 ⁻⁵ Torr.
About 0 ° C. is preferable.

The hole injection electrode is preferably a transparent or translucent electrode for extracting emitted light. As the transparent electrode, ITO (tin-doped indium oxide), IZO
(Zinc-doped indium oxide), ZnO, SnO ₂ , I
Examples include n ₂ O ₃ , and preferably ITO (tin-doped indium oxide) and IZO (zinc-doped indium oxide). ITO usually contains In ₂ O ₃ and SnO in a stoichiometric composition, but the amount of O may slightly deviate from this. When transparency is not required, the hole injection electrode may be made of a known opaque metal material.

The thickness of the hole injecting electrode may be a certain value or more so as to sufficiently inject holes, and is preferably 5 or more.
The range is preferably from 0 to 500 nm, more preferably from 50 to 300 nm. The upper limit is not particularly limited, but if the thickness is too large, there is a fear of peeling or the like. If the thickness is too small, there is a problem in the film strength at the time of manufacturing, the hole transport ability, and the resistance value.

This hole injecting electrode layer can be formed by a vapor deposition method or the like, but is preferably a sputtering method, particularly a pulse D method.
It is preferable to form by the C sputtering method.

The organic layer of the organic EL structure can have the following configuration. The light emitting layer has a function of injecting holes (holes) and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

The hole injecting / transporting layer has a function of facilitating the injection of holes from the hole injecting electrode, a function of stably transporting holes, and a function of hindering electrons.
The electron injection transport layer has a function of facilitating injection of electrons from the electron injection electrode, a function of stably transporting electrons, and a function of preventing holes. These layers increase and confine holes and electrons injected into the light emitting layer, optimize the recombination region, and improve luminous efficiency.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited, and vary depending on the forming method.
It is preferable that the thickness be in the range of 10 to 300 nm.

The thickness of the hole injecting / transporting layer and the thickness of the electron injecting / transporting layer depend on the design of the recombination / light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. When the hole or electron injection layer and the transport layer are separated from each other, it is preferable that the injection layer has a thickness of 1 nm or more and the transport layer has a thickness of 1 nm or more. At this time, the upper limit of the thickness of the injection layer and the transport layer is usually about 500 nm for the injection layer and 500 nm for the transport layer.
It is about. Such a film thickness is the same when two injection / transport layers are provided.

The light emitting layer of the organic EL device contains a fluorescent substance which is a compound having a light emitting function. Examples of such a fluorescent substance include, for example, JP-A-63-26469.
No. 2 discloses at least one compound selected from compounds such as quinacridone, rubrene, and styryl dyes. Also, Tris (8
Quinolinol derivatives such as metal complex dyes having 8-quinolinol or a derivative thereof as a ligand, such as (quinolinolato) aluminum; tetraphenylbutadiene, anthracene, perylene, coronene, and 12-phthaloperinone derivatives. Further, phenylanthracene derivatives described in JP-A-8-12600 (Japanese Patent Application No. 6-110569), tetraarylethene derivatives described in JP-A-8-12969 (Japanese Patent Application No. 6-114456), and the like are used. be able to.

Further, it is preferable to use in combination with a host substance capable of emitting light by itself, and it is preferable to use it as a dopant. In such a case, the content of the compound in the light emitting layer is preferably 0.01 to 20% by volume, more preferably 0.1 to 15% by volume. In particular, for a rubrene-based material, the content is preferably 0.01 to 20% by volume. By using in combination with the host substance,
The emission wavelength characteristic of the host material can be changed, light emission shifted to a longer wavelength becomes possible, and the emission efficiency and stability of the device are improved.

As the host substance, a quinolinolato complex is preferable, and an aluminum complex having 8-quinolinol or a derivative thereof as a ligand is preferable. Such an aluminum complex is disclosed in JP-A-63-26469.
No. 2, JP-A-3-255190, JP-A-5-7073
3, JP-A-5-258859, JP-A-6-2158
No. 74 and the like.

Specifically, first, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis (benzo {f} -8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) aluminum Oxide, tris (8-quinolinolato) indium,
Tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-
8-quinolinolato) gallium, bis (5-chloro-8-
Quinolinolato) calcium, 5,7-dichloro-8-quinolinolatoaluminum, tris (5,7-dibromo-
8-hydroxyquinolinolato) aluminum and poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane].

Other host materials are disclosed in
Phenylanthracene derivative described in JP-A-12600 (Japanese Patent Application No. 6-110569) and JP-A-8-1296
No. 9 (Japanese Patent Application No. 6-114456) is also preferable.

The light emitting layer may also serve as an electron injection / transport layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. These fluorescent substances may be deposited.

The light emitting layer is preferably a mixed layer of at least one kind of hole injecting and transporting compound and at least one kind of electron injecting and transporting compound, if necessary.
Further, it is preferable that a dopant is contained in the mixed layer. The content of the compound in such a mixed layer is 0.01 to 20% by volume, further 0.1 to 15% by volume.
% Is preferable.

In the mixed layer, a carrier hopping conduction path is formed, so that each carrier moves in a material having a favorable polarity and injection of a carrier having the opposite polarity is unlikely to occur, so that the organic compound is less likely to be damaged. This has the advantage that the element life is extended. Further, by including the above-described dopant in such a mixed layer, the emission wavelength characteristics of the mixed layer itself can be changed, the emission wavelength can be shifted to a longer wavelength, and the emission intensity is increased, The stability of the device can be improved.

The hole injecting / transporting compound and the electron injecting / transporting compound used in the mixed layer may be selected from a compound for a hole injecting / transporting layer and a compound for an electron injecting / transporting layer, respectively, which will be described later. Among them, compounds for the hole injection transport layer include amine derivatives having strong fluorescence,
For example, it is preferable to use a triphenyldiamine derivative which is a hole transport material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring.

As the compound capable of injecting and transporting electrons, it is preferable to use a quinoline derivative, furthermore a metal complex having 8-quinolinol or its derivative as a ligand, particularly tris (8-quinolinolato) aluminum (Alq3). It is also preferable to use the above-mentioned phenylanthracene derivatives and tetraarylethene derivatives.

As the compound for the hole injecting and transporting layer, an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative which is the above-described hole transporting material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring is used. Is preferred.

The mixing ratio in this case depends on the respective carrier mobility and carrier concentration. In general, the weight ratio of the compound of the hole injecting and transporting compound / the compound having the electron injecting and transporting function is 1/99 to less. 99/1, more preferably 10/90 to 90/10, particularly preferably 20/80
It is preferable to set it to about 80/20.

The thickness of the mixed layer is preferably not less than the thickness of one molecular layer and less than the thickness of the organic compound layer. Specifically, the thickness is preferably 1 to 85 nm, more preferably 5 to 60 nm, particularly preferably 5 to 50 nm.

As a method of forming the mixed layer, co-evaporation in which evaporation is performed from different evaporation sources is preferable. However, when the vapor pressures (evaporation temperatures) are approximately the same or very close, they are mixed in advance in the same evaporation boat. Alternatively, it can be deposited. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may exist in an island shape. The light-emitting layer is generally formed to a predetermined thickness by vapor-depositing an organic fluorescent substance or by dispersing and coating the resin in a resin binder.

The hole injecting and transporting layer is described in, for example,
JP-A-3-295695, JP-A-2-191694, JP-A-3-792, JP-A-5-234681
JP, JP-A-5-239455, JP-A-5-5-2
JP-A-99174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100172
Various organic compounds described in JP-A No. 06509555 A1 and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD), an aromatic tertiary amine,
Examples include hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having an amino group, and polythiophene. These compounds may be used alone or in combination of two or more. When two or more kinds are used in combination, they may be stacked as separate layers or mixed.

When the hole injecting and transporting layer is divided into a hole injecting layer and a hole transporting layer, a preferred combination can be selected from compounds having a hole injecting and transporting property. At this time, it is preferable to laminate the compounds in order from the hole injecting electrode (ITO or the like) with the smallest ionization potential. Further, it is preferable to use a compound having a good thin film property on the surface of the hole injection electrode. Such a stacking order is the same when two or more hole injection transport layers are provided. With such a stacking order, the driving voltage is reduced, and the occurrence of current leakage and the occurrence and growth of dark spots can be prevented. In addition, in the case of forming an element, since a thin film of about 1 to 10 nm can be made uniform and pinhole-free because evaporation is used,
Even if a compound having a small ionization potential and having absorption in the visible region is used for the hole injection layer, it is possible to prevent a change in the color tone of the emission color and a decrease in efficiency due to reabsorption. The hole injecting and transporting layer can be formed by vapor deposition of the above compound in the same manner as the light emitting layer and the like.

The electron injecting / transporting layer includes quinoline derivatives such as organometallic complexes having 8-quinolinol such as tris (8-quinolinolato) aluminum (Alq3) or derivatives thereof as ligands, oxadiazole derivatives, perylene derivatives, and the like. A pyridine derivative, a pyrimidine derivative, a quinoxaline derivative, a diphenylquinone derivative, a nitro-substituted fluorene derivative, or the like can be used. The electron injection / transport layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The electron injecting and transporting layer may be formed by vapor deposition or the like, similarly to the light emitting layer.

In the case where the electron injecting and transporting layer is divided into an electron injecting layer and an electron transporting layer, a preferable combination can be selected from the electron injecting and transporting compounds. At this time, it is preferable to stack the compounds in descending order of the electron affinity value from the electron injection electrode side. Such a stacking order is the same when two or more electron injection / transport layers are provided.

For forming the hole injection transport layer, the light emitting layer and the electron injection transport layer, a uniform thin film can be formed.
It is preferable to use a vacuum deposition method. When vacuum deposition is used, the amorphous state or the crystal grain size is 0.2 μm
The following homogeneous thin film is obtained. If the crystal grain size exceeds 0.2 μm, the light emission becomes non-uniform, the driving voltage of the device must be increased, and the charge injection efficiency is significantly reduced.

The conditions for vacuum deposition are not particularly limited.
The degree of vacuum is 0 ^-4 Pa or less, and the deposition rate is 0.01 to 1 nm /
It is preferable to set it to about sec. Further, it is preferable to form each layer continuously in a vacuum. If they are formed continuously in a vacuum, impurities can be prevented from adsorbing at the interface between the layers, so that high characteristics can be obtained. Further, the driving voltage of the element can be reduced, and the occurrence and growth of dark spots can be suppressed.

In the case where a plurality of compounds are contained in one layer when a vacuum evaporation method is used for forming each of these layers, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

The emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

For the color filter film, a color filter used in a liquid crystal display or the like may be used.
The characteristics of the color filter may be adjusted in accordance with the light emitted from the organic EL element to optimize the extraction efficiency and the color purity.

If a color filter capable of cutting off short-wavelength external light that is absorbed by the EL element material or the fluorescence conversion layer is used, the light resistance of the element and the display contrast are improved.

An optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The fluorescence conversion filter film absorbs EL light and emits light from the phosphor in the fluorescence conversion film, thereby performing color conversion of the emission color. It is formed from a fluorescent material and a light absorbing material.

As the fluorescent material, basically, a material having a high fluorescence quantum yield may be used, and it is desirable that the fluorescent material has strong absorption in the EL emission wavelength region. In practice, laser dyes and the like are suitable, and rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalocyanines, etc.) naphthalimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds A styryl compound, a coumarin compound or the like may be used.

As the binder, basically, a material that does not quench the fluorescence may be selected, and a binder that can be finely patterned by photolithography, printing, or the like is preferable. In the case where the hole injection electrode is formed on the substrate in contact with the hole injection electrode, a material which is not damaged when the hole injection electrode (ITO, IZO) is formed is preferable.

The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may be omitted when unnecessary. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

The organic EL device of the present invention is generally used as a DC-driven or pulse-driven EL device.
The applied voltage is usually about 2 to 30V.

[0108]

EXAMPLE An amorphous silicon layer having a thickness of about 600 DEG was formed on a 1737 heat-resistant alkali-free glass substrate manufactured by Corning by low pressure CVD (LPCVD). The film forming conditions are as follows. Si ₂ H ₆ gas: 100 SCCM, pressure: 0.3 Torr, temperature: 480 ° C.

Then, this amorphous silicon layer was solid-phase grown to form an active layer (polysilicon layer). This solid phase growth used both thermal annealing and laser annealing. The conditions are as follows.

<Thermal annealing> N ₂ : 1 SLM, temperature: 600 ° C., processing time: 24 hours

<Laser annealing> KrF: 254 nm, energy density: 200 mJ / cm ² ,
Number of shots: 200

Next, this polysilicon layer was patterned to obtain an active silicon layer: 500 °.

A gate oxide film is formed on the active silicon layer.
Becomes SiO_TwoThe layer is formed, for example, by a plasma CVD method.
A film was formed at 800 °. The film forming conditions are as follows, for example.
You. Input power: 50W, TEOS (tetraethoxysila
G) Gas: 50 SCCM, O _Two: 500 SCCM, pressure: 0.1
0.5 Torr, temperature: 350 ° C.

On this SiO ₂ layer, a Mo—Si ₂ layer serving as a gate electrode was formed to a thickness of about 1000 ° by a sputtering method. Then, the Mo—Si ₂ layer and the SiO ₂ layer formed above were patterned by, for example, dry etching to obtain a gate electrode and a gate oxide film.

Then, as shown in FIG.
And a masking region with a photoresist 105 is patterned thereon to mask a lightly doped region.
Using the gate electrode 05 and the gate electrode as a mask, an N-type impurity: P was doped by ion doping in portions to be the source / drain regions of the silicon active layer.
The conditions at this time are as follows: acceleration voltage: 65 keV, dose amount: 1
× 10 ¹⁵ cm ^-2 .

Next, the photoresist 105 is removed,
First switching for driving a pixel having an LDD structure by doping an N-type impurity: P into a low concentration doping region and a high concentration doping region of a silicon active layer by an ion doping method using a gate electrode as a mask. An element was formed. The condition at this time is as follows: acceleration voltage: 65
The keV and the dose were set to 1 × 10 ¹³ cm ⁻² .

Next, this was heated in a nitrogen atmosphere at about 550 ° C. for 10 hours to activate the dopant. Further, hydrogenation was performed by heat treatment at about 400 ° C. for 30 minutes in a hydrogen atmosphere to reduce the defect state density of the semiconductor.

Then, an SiO ₂ layer serving as an interlayer insulating layer was formed on the entire substrate to a thickness of about 8000 mm. The conditions for forming the SiO ₂ film serving as the interlayer insulating layer are as follows. O ₂ / N ₂ : 10 SLM 5% SiH ₄ / N ₂ : 1 SLM 1% PH ₃ / N ₂ : 500 SCCM N ₂ : 10 SLM Temperature: 410 ° C. Pressure: atmospheric pressure

The SiO ₂ film serving as the interlayer insulating layer was etched to form a contact hole. Next, Al was deposited as a drain and source wiring electrode.

Further, a comparative sample was prepared in the same manner as described above except that the LDD structure was not used.

When the off-state leakage current and Ioff of each switching element of the obtained TFT array were determined under the same conditions, when the completed channel length was 3 μm, the sample of the present invention was 1 × 10 ⁻⁹ A or less. On the other hand, the comparative sample was 1 × 10 ⁻⁷ A or more.

Next, an ITO film serving as a hole injection electrode was formed in a region where the organic EL element was to be formed, and was connected to the wiring electrode. Then, in order to emit light only in the light emitting region (pixel portion), the interlayer insulating film SiO ₂ is formed in a thickness of 4000
A film was formed, and a portion serving as a light emitting region was opened.

An organic layer including a light emitting layer was formed on the pixel region (on the ITO) of the thin film pattern of the sample TFT of the present invention produced as described above by a vacuum evaporation method. The materials formed are as follows. Here, only one example is given, but as is clear from the concept, the present invention can be applied irrespective of a film forming material as long as it can be formed by an evaporation method.

As a hole injection layer and a hole transport layer,
N, N'-bis (m-methylphenyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (N,
N´-bis (m-methyl phenyl) -N, N´-diphenyl-1,1´-biph
enyl-4,4′-diamine or abbreviated as TPD), and tris (8-hydroxyquinoline) aluminum (hereinafter A)
lq3), the second electrode 1 without breaking the vacuum.
As No. 2, a cathode was continuously formed.

As a film forming method, a vacuum injection method was selected for the hole injection layer and the hole transport layer, and a DC sputtering method was selected for the second electrode. As the second electrode, an Al / Li alloy (L
i concentration: 7 at%) with a gas pressure of 1 Pa, a power of 1 W / cm ² and a film thickness of 5 nm.
The film was laminated at a thickness of 200 nm with a power of 3 Pa and a power of 1 W / cm ² .

Each pixel of the obtained organic EL display device is set to 1
When the device was driven in a time-division manner so as to have a constant current of 10 mA / cm ² per pixel, and the contrast was evaluated from the ratio of the brightness of the entire screen during light emission and during non-light emission, the sample of the present invention was found to be 1:80. In contrast, the comparative sample was 1:10.

As is clear from the gist, the present invention is not limited to the organic EL element constituting films used in this embodiment and the order of lamination thereof, but includes a hole injection layer, a light emitting layer, a second electrode, and a wiring electrode. May be used, and a hole injection layer, an electron transport layer, an electron injection layer, and the like may be further formed to form a multilayer structure. In other words, the type of material to be deposited,
Applicable regardless of the structure.

[0128]

As described above, according to the present invention, high voltage,
A driving device for an organic EL device capable of performing high-resolution switching and capable of performing high-definition display without erroneous light emission and a decrease in contrast by using a switching device having a small off-current. The display device used can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an element configuration of a driving device of an organic EL element of the present invention.

FIG. 2 is a plan view showing an example of a driving device for an organic EL element of the present invention.

FIG. 3 is a partial cross-sectional view illustrating a manufacturing process of a drive device for an organic EL element of the present invention.

FIG. 4 is a partial cross-sectional view showing a manufacturing process of the driving device for an organic EL element of the present invention.

FIG. 5 is a partial cross-sectional view showing a manufacturing process of the driving device for an organic EL element of the present invention.

FIG. 6 is a partial cross-sectional view showing a manufacturing process of the driving device for the organic EL element of the present invention.

FIG. 7 is a partial cross-sectional view showing a manufacturing process of the driving device for the organic EL element of the present invention.

FIG. 8 is a partial cross-sectional view showing a manufacturing process of the drive device for the organic EL element of the present invention.

FIG. 9 is a partial cross-sectional view showing a manufacturing process of the drive device for an organic EL element of the present invention.

FIG. 10 is a partial cross-sectional view showing a step of manufacturing an organic EL element driving device according to the present invention.

FIG. 11 is a partial cross-sectional view showing a connection structure between a driving device of an organic EL device of the present invention and electrodes of the device.

FIG. 12 is a block diagram illustrating a configuration example of an organic EL display device.

FIG. 13 is an enlarged view of a portion A in FIG.

[Explanation of symbols]

 Reference Signs List 1 gate 2 silicon base 11 source bus 12 gate bus 13 source electrode 14 drain electrode 15 gate line 16 drain electrode 17 source electrode 18 capacitor 21, 22 silicon base 101 substrate 102 amorphous silicon layer 102a active layer 103 gate oxide film 104 gate electrode 105 Insulating film 106 resist

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference)

Claims (3)

[Claims] 1. An organic EL element comprising: a switching element for driving an organic EL element; and an organic EL element driven by the switching element and having at least an organic layer involved in a light emitting function, wherein the switching element has an LDD structure. Drive. 2. The organic EL element driving device according to claim 1, wherein the switching element is a depression type. 3. A plurality of organic Es arranged in a matrix.
3. An organic EL display device comprising the L element and the organic EL element driving device according to claim 1, which drives the organic EL element.